Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

176 files changed, 21493 insertions, 0 deletions

diff --git a/dom/smil/SMILAnimationController.cpp b/dom/smil/SMILAnimationController.cpp
new file mode 100644
index 0000000000..2c103b0f16
--- /dev/null
+++ b/dom/smil/SMILAnimationController.cpp
@@ -0,0 +1,700 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILAnimationController.h"
+
+#include <algorithm>
+
+#include "mozilla/AutoRestore.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/PresShellInlines.h"
+#include "mozilla/RestyleManager.h"
+#include "mozilla/SMILTimedElement.h"
+#include "mozilla/dom/DocumentInlines.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/SVGAnimationElement.h"
+#include "nsContentUtils.h"
+#include "nsCSSProps.h"
+#include "nsRefreshDriver.h"
+#include "mozilla/dom/Document.h"
+#include "SMILCompositor.h"
+#include "SMILCSSProperty.h"
+
+using namespace mozilla::dom;
+
+namespace mozilla {
+
+//----------------------------------------------------------------------
+// SMILAnimationController implementation
+
+//----------------------------------------------------------------------
+// ctors, dtors, factory methods
+
+SMILAnimationController::SMILAnimationController(Document* aDoc)
+    : mDocument(aDoc) {
+  MOZ_ASSERT(aDoc, "need a non-null document");
+
+  if (nsRefreshDriver* refreshDriver = GetRefreshDriver()) {
+    mStartTime = refreshDriver->MostRecentRefresh();
+  } else {
+    mStartTime = mozilla::TimeStamp::Now();
+  }
+  mCurrentSampleTime = mStartTime;
+
+  Begin();
+}
+
+SMILAnimationController::~SMILAnimationController() {
+  NS_ASSERTION(mAnimationElementTable.IsEmpty(),
+               "Animation controller shouldn't be tracking any animation"
+               " elements when it dies");
+  NS_ASSERTION(!mRegisteredWithRefreshDriver,
+               "Leaving stale entry in refresh driver's observer list");
+}
+
+void SMILAnimationController::Disconnect() {
+  MOZ_ASSERT(mDocument, "disconnecting when we weren't connected...?");
+  MOZ_ASSERT(mRefCnt.get() == 1,
+             "Expecting to disconnect when doc is sole remaining owner");
+  NS_ASSERTION(mPauseState & SMILTimeContainer::PAUSE_PAGEHIDE,
+               "Expecting to be paused for pagehide before disconnect");
+
+  StopSampling(GetRefreshDriver());
+
+  mDocument = nullptr;  // (raw pointer)
+}
+
+//----------------------------------------------------------------------
+// SMILTimeContainer methods:
+
+void SMILAnimationController::Pause(uint32_t aType) {
+  SMILTimeContainer::Pause(aType);
+  UpdateSampling();
+}
+
+void SMILAnimationController::Resume(uint32_t aType) {
+  bool wasPaused = !!mPauseState;
+  // Update mCurrentSampleTime so that calls to GetParentTime--used for
+  // calculating parent offsets--are accurate
+  mCurrentSampleTime = mozilla::TimeStamp::Now();
+
+  SMILTimeContainer::Resume(aType);
+
+  if (wasPaused && !mPauseState) {
+    UpdateSampling();
+  }
+}
+
+SMILTime SMILAnimationController::GetParentTime() const {
+  return (SMILTime)(mCurrentSampleTime - mStartTime).ToMilliseconds();
+}
+
+//----------------------------------------------------------------------
+// nsARefreshObserver methods:
+NS_IMPL_ADDREF(SMILAnimationController)
+NS_IMPL_RELEASE(SMILAnimationController)
+
+// nsRefreshDriver Callback function
+void SMILAnimationController::WillRefresh(mozilla::TimeStamp aTime) {
+  // Although we never expect aTime to go backwards, when we initialise the
+  // animation controller, if we can't get hold of a refresh driver we
+  // initialise mCurrentSampleTime to Now(). It may be possible that after
+  // doing so we get sampled by a refresh driver whose most recent refresh time
+  // predates when we were initialised, so to be safe we make sure to take the
+  // most recent time here.
+  aTime = std::max(mCurrentSampleTime, aTime);
+
+  // Sleep detection: If the time between samples is a whole lot greater than we
+  // were expecting then we assume the computer went to sleep or someone's
+  // messing with the clock. In that case, fiddle our parent offset and use our
+  // average time between samples to calculate the new sample time. This
+  // prevents us from hanging while trying to catch up on all the missed time.
+
+  // Smoothing of coefficient for the average function. 0.2 should let us track
+  // the sample rate reasonably tightly without being overly affected by
+  // occasional delays.
+  static const double SAMPLE_DUR_WEIGHTING = 0.2;
+  // If the elapsed time exceeds our expectation by this number of times we'll
+  // initiate special behaviour to basically ignore the intervening time.
+  static const double SAMPLE_DEV_THRESHOLD = 200.0;
+
+  SMILTime elapsedTime =
+      (SMILTime)(aTime - mCurrentSampleTime).ToMilliseconds();
+  if (mAvgTimeBetweenSamples == 0) {
+    // First sample.
+    mAvgTimeBetweenSamples = elapsedTime;
+  } else {
+    if (elapsedTime > SAMPLE_DEV_THRESHOLD * mAvgTimeBetweenSamples) {
+      // Unexpectedly long delay between samples.
+      NS_WARNING(
+          "Detected really long delay between samples, continuing from "
+          "previous sample");
+      mParentOffset += elapsedTime - mAvgTimeBetweenSamples;
+    }
+    // Update the moving average. Due to truncation here the average will
+    // normally be a little less than it should be but that's probably ok.
+    mAvgTimeBetweenSamples =
+        (SMILTime)(elapsedTime * SAMPLE_DUR_WEIGHTING +
+                   mAvgTimeBetweenSamples * (1.0 - SAMPLE_DUR_WEIGHTING));
+  }
+  mCurrentSampleTime = aTime;
+
+  Sample();
+}
+
+//----------------------------------------------------------------------
+// Animation element registration methods:
+
+void SMILAnimationController::RegisterAnimationElement(
+    SVGAnimationElement* aAnimationElement) {
+  const bool wasEmpty = mAnimationElementTable.IsEmpty();
+  mAnimationElementTable.PutEntry(aAnimationElement);
+  if (wasEmpty) {
+    UpdateSampling();
+  }
+}
+
+void SMILAnimationController::UnregisterAnimationElement(
+    SVGAnimationElement* aAnimationElement) {
+  mAnimationElementTable.RemoveEntry(aAnimationElement);
+  if (mAnimationElementTable.IsEmpty()) {
+    UpdateSampling();
+  }
+}
+
+//----------------------------------------------------------------------
+// Page show/hide
+
+void SMILAnimationController::OnPageShow() {
+  Resume(SMILTimeContainer::PAUSE_PAGEHIDE);
+}
+
+void SMILAnimationController::OnPageHide() {
+  Pause(SMILTimeContainer::PAUSE_PAGEHIDE);
+}
+
+//----------------------------------------------------------------------
+// Cycle-collection support
+
+void SMILAnimationController::Traverse(
+    nsCycleCollectionTraversalCallback* aCallback) {
+  // Traverse last compositor table
+  if (mLastCompositorTable) {
+    for (SMILCompositor& compositor : *mLastCompositorTable) {
+      compositor.Traverse(aCallback);
+    }
+  }
+}
+
+void SMILAnimationController::Unlink() { mLastCompositorTable = nullptr; }
+
+//----------------------------------------------------------------------
+// Refresh driver lifecycle related methods
+
+void SMILAnimationController::NotifyRefreshDriverCreated(
+    nsRefreshDriver* aRefreshDriver) {
+  UpdateSampling();
+}
+
+void SMILAnimationController::NotifyRefreshDriverDestroying(
+    nsRefreshDriver* aRefreshDriver) {
+  StopSampling(aRefreshDriver);
+}
+
+//----------------------------------------------------------------------
+// Timer-related implementation helpers
+
+bool SMILAnimationController::ShouldSample() const {
+  return !mPauseState && !mAnimationElementTable.IsEmpty() &&
+         !mChildContainerTable.IsEmpty();
+}
+
+void SMILAnimationController::UpdateSampling() {
+  const bool shouldSample = ShouldSample();
+  const bool isSampling = mRegisteredWithRefreshDriver;
+  if (shouldSample == isSampling) {
+    return;
+  }
+
+  nsRefreshDriver* driver = GetRefreshDriver();
+  if (!driver) {
+    return;
+  }
+
+  if (shouldSample) {
+    // We're effectively resuming from a pause so update our current sample time
+    // or else it will confuse our "average time between samples" calculations.
+    mCurrentSampleTime = mozilla::TimeStamp::Now();
+    driver->AddRefreshObserver(this, FlushType::Style, "SMIL animations");
+    mRegisteredWithRefreshDriver = true;
+    Sample();  // Run the first sample manually.
+  } else {
+    StopSampling(driver);
+  }
+}
+
+void SMILAnimationController::StopSampling(nsRefreshDriver* aRefreshDriver) {
+  if (aRefreshDriver && mRegisteredWithRefreshDriver) {
+    // NOTE: The document might already have been detached from its PresContext
+    // (and RefreshDriver), which would make GetRefreshDriver() return null.
+    MOZ_ASSERT(!GetRefreshDriver() || aRefreshDriver == GetRefreshDriver(),
+               "Stopping sampling with wrong refresh driver");
+    aRefreshDriver->RemoveRefreshObserver(this, FlushType::Style);
+    mRegisteredWithRefreshDriver = false;
+  }
+}
+
+//----------------------------------------------------------------------
+// Sample-related methods and callbacks
+
+void SMILAnimationController::DoSample() {
+  DoSample(true);  // Skip unchanged time containers
+}
+
+void SMILAnimationController::DoSample(bool aSkipUnchangedContainers) {
+  if (!mDocument) {
+    NS_ERROR("Shouldn't be sampling after document has disconnected");
+    return;
+  }
+  if (mRunningSample) {
+    NS_ERROR("Shouldn't be recursively sampling");
+    return;
+  }
+
+  bool isStyleFlushNeeded = mResampleNeeded;
+  mResampleNeeded = false;
+
+  nsCOMPtr<Document> document(mDocument);  // keeps 'this' alive too
+
+  // Set running sample flag -- do this before flushing styles so that when we
+  // flush styles we don't end up requesting extra samples
+  AutoRestore<bool> autoRestoreRunningSample(mRunningSample);
+  mRunningSample = true;
+
+  // STEP 1: Bring model up to date
+  // (i)  Rewind elements where necessary
+  // (ii) Run milestone samples
+  RewindElements();
+  DoMilestoneSamples();
+
+  // STEP 2: Sample the child time containers
+  //
+  // When we sample the child time containers they will simply record the sample
+  // time in document time.
+  TimeContainerHashtable activeContainers(mChildContainerTable.Count());
+  for (SMILTimeContainer* container : mChildContainerTable.Keys()) {
+    if (!container) {
+      continue;
+    }
+
+    if (!container->IsPausedByType(SMILTimeContainer::PAUSE_BEGIN) &&
+        (container->NeedsSample() || !aSkipUnchangedContainers)) {
+      container->ClearMilestones();
+      container->Sample();
+      container->MarkSeekFinished();
+      activeContainers.PutEntry(container);
+    }
+  }
+
+  // STEP 3: (i)  Sample the timed elements AND
+  //         (ii) Create a table of compositors
+  //
+  // (i) Here we sample the timed elements (fetched from the
+  // SVGAnimationElements) which determine from the active time if the
+  // element is active and what its simple time etc. is. This information is
+  // then passed to its time client (SMILAnimationFunction).
+  //
+  // (ii) During the same loop we also build up a table that contains one
+  // compositor for each animated attribute and which maps animated elements to
+  // the corresponding compositor for their target attribute.
+  //
+  // Note that this compositor table needs to be allocated on the heap so we can
+  // store it until the next sample. This lets us find out which elements were
+  // animated in sample 'n-1' but not in sample 'n' (and hence need to have
+  // their animation effects removed in sample 'n').
+  //
+  // Parts (i) and (ii) are not functionally related but we combine them here to
+  // save iterating over the animation elements twice.
+
+  // Create the compositor table
+  UniquePtr<SMILCompositorTable> currentCompositorTable(
+      new SMILCompositorTable(0));
+  nsTArray<RefPtr<SVGAnimationElement>> animElems(
+      mAnimationElementTable.Count());
+
+  for (SVGAnimationElement* animElem : mAnimationElementTable.Keys()) {
+    SampleTimedElement(animElem, &activeContainers);
+    AddAnimationToCompositorTable(animElem, currentCompositorTable.get(),
+                                  isStyleFlushNeeded);
+    animElems.AppendElement(animElem);
+  }
+  activeContainers.Clear();
+
+  // STEP 4: Compare previous sample's compositors against this sample's.
+  // (Transfer cached base values across, & remove animation effects from
+  // no-longer-animated targets.)
+  if (mLastCompositorTable) {
+    // * Transfer over cached base values, from last sample's compositors
+    for (SMILCompositor& compositor : *currentCompositorTable) {
+      SMILCompositor* lastCompositor =
+          mLastCompositorTable->GetEntry(compositor.GetKey());
+
+      if (lastCompositor) {
+        compositor.StealCachedBaseValue(lastCompositor);
+        if (!lastCompositor->HasSameNumberOfAnimationFunctionsAs(compositor)) {
+          // If we have multiple animations on the same element, they share a
+          // compositor. If an active animation ends, it will no longer be in
+          // the compositor table. We need to force compositing to ensure we
+          // render the element with any remaining frozen animations even though
+          // they would not normally trigger compositing.
+          compositor.ToggleForceCompositing();
+        }
+      }
+    }
+
+    // * For each compositor in current sample's hash table, remove entry from
+    // prev sample's hash table -- we don't need to clear animation
+    // effects of those compositors, since they're still being animated.
+    for (const auto& key : currentCompositorTable->Keys()) {
+      mLastCompositorTable->RemoveEntry(key);
+    }
+
+    // * For each entry that remains in prev sample's hash table (i.e. for
+    // every target that's no longer animated), clear animation effects.
+    for (SMILCompositor& compositor : *mLastCompositorTable) {
+      compositor.ClearAnimationEffects();
+    }
+  }
+
+  // return early if there are no active animations to avoid a style flush
+  if (currentCompositorTable->IsEmpty()) {
+    mLastCompositorTable = nullptr;
+    return;
+  }
+
+  if (isStyleFlushNeeded) {
+    document->FlushPendingNotifications(FlushType::Style);
+  }
+
+  // WARNING:
+  // WARNING: the above flush may have destroyed the pres shell and/or
+  // WARNING: frames and other layout related objects.
+  // WARNING:
+
+  // STEP 5: Compose currently-animated attributes.
+  // XXXdholbert: This step traverses our animation targets in an effectively
+  // random order. For animation from/to 'inherit' values to work correctly
+  // when the inherited value is *also* being animated, we really should be
+  // traversing our animated nodes in an ancestors-first order (bug 501183)
+  bool mightHavePendingStyleUpdates = false;
+  for (auto& compositor : *currentCompositorTable) {
+    compositor.ComposeAttribute(mightHavePendingStyleUpdates);
+  }
+
+  // Update last compositor table
+  mLastCompositorTable = std::move(currentCompositorTable);
+  mMightHavePendingStyleUpdates = mightHavePendingStyleUpdates;
+
+  NS_ASSERTION(!mResampleNeeded, "Resample dirty flag set during sample!");
+}
+
+void SMILAnimationController::RewindElements() {
+  const bool rewindNeeded = std::any_of(
+      mChildContainerTable.Keys().cbegin(), mChildContainerTable.Keys().cend(),
+      [](SMILTimeContainer* container) { return container->NeedsRewind(); });
+
+  if (!rewindNeeded) return;
+
+  for (SVGAnimationElement* animElem : mAnimationElementTable.Keys()) {
+    SMILTimeContainer* timeContainer = animElem->GetTimeContainer();
+    if (timeContainer && timeContainer->NeedsRewind()) {
+      animElem->TimedElement().Rewind();
+    }
+  }
+
+  for (SMILTimeContainer* container : mChildContainerTable.Keys()) {
+    container->ClearNeedsRewind();
+  }
+}
+
+void SMILAnimationController::DoMilestoneSamples() {
+  // We need to sample the timing model but because SMIL operates independently
+  // of the frame-rate, we can get one sample at t=0s and the next at t=10min.
+  //
+  // In between those two sample times a whole string of significant events
+  // might be expected to take place: events firing, new interdependencies
+  // between animations resolved and dissolved, etc.
+  //
+  // Furthermore, at any given time, we want to sample all the intervals that
+  // end at that time BEFORE any that begin. This behaviour is implied by SMIL's
+  // endpoint-exclusive timing model.
+  //
+  // So we have the animations (specifically the timed elements) register the
+  // next significant moment (called a milestone) in their lifetime and then we
+  // step through the model at each of these moments and sample those animations
+  // registered for those times. This way events can fire in the correct order,
+  // dependencies can be resolved etc.
+
+  SMILTime sampleTime = INT64_MIN;
+
+  while (true) {
+    // We want to find any milestones AT OR BEFORE the current sample time so we
+    // initialise the next milestone to the moment after (1ms after, to be
+    // precise) the current sample time and see if there are any milestones
+    // before that. Any other milestones will be dealt with in a subsequent
+    // sample.
+    SMILMilestone nextMilestone(GetCurrentTimeAsSMILTime() + 1, true);
+    for (SMILTimeContainer* container : mChildContainerTable.Keys()) {
+      if (container->IsPausedByType(SMILTimeContainer::PAUSE_BEGIN)) {
+        continue;
+      }
+      SMILMilestone thisMilestone;
+      bool didGetMilestone =
+          container->GetNextMilestoneInParentTime(thisMilestone);
+      if (didGetMilestone && thisMilestone < nextMilestone) {
+        nextMilestone = thisMilestone;
+      }
+    }
+
+    if (nextMilestone.mTime > GetCurrentTimeAsSMILTime()) {
+      break;
+    }
+
+    nsTArray<RefPtr<dom::SVGAnimationElement>> elements;
+    for (SMILTimeContainer* container : mChildContainerTable.Keys()) {
+      if (container->IsPausedByType(SMILTimeContainer::PAUSE_BEGIN)) {
+        continue;
+      }
+      container->PopMilestoneElementsAtMilestone(nextMilestone, elements);
+    }
+
+    // During the course of a sampling we don't want to actually go backwards.
+    // Due to negative offsets, early ends and the like, a timed element might
+    // register a milestone that is actually in the past. That's fine, but it's
+    // still only going to get *sampled* with whatever time we're up to and no
+    // earlier.
+    //
+    // Because we're only performing this clamping at the last moment, the
+    // animations will still all get sampled in the correct order and
+    // dependencies will be appropriately resolved.
+    sampleTime = std::max(nextMilestone.mTime, sampleTime);
+
+    for (RefPtr<dom::SVGAnimationElement>& elem : elements) {
+      MOZ_ASSERT(elem, "nullptr animation element in list");
+      SMILTimeContainer* container = elem->GetTimeContainer();
+      if (!container)
+        // The container may be nullptr if the element has been detached from
+        // its parent since registering a milestone.
+        continue;
+
+      SMILTimeValue containerTimeValue =
+          container->ParentToContainerTime(sampleTime);
+      if (!containerTimeValue.IsDefinite()) continue;
+
+      // Clamp the converted container time to non-negative values.
+      SMILTime containerTime =
+          std::max<SMILTime>(0, containerTimeValue.GetMillis());
+
+      if (nextMilestone.mIsEnd) {
+        elem->TimedElement().SampleEndAt(containerTime);
+      } else {
+        elem->TimedElement().SampleAt(containerTime);
+      }
+    }
+  }
+}
+
+/*static*/
+void SMILAnimationController::SampleTimedElement(
+    SVGAnimationElement* aElement, TimeContainerHashtable* aActiveContainers) {
+  SMILTimeContainer* timeContainer = aElement->GetTimeContainer();
+  if (!timeContainer) return;
+
+  // We'd like to call timeContainer->NeedsSample() here and skip all timed
+  // elements that belong to paused time containers that don't need a sample,
+  // but that doesn't work because we've already called Sample() on all the time
+  // containers so the paused ones don't need a sample any more and they'll
+  // return false.
+  //
+  // Instead we build up a hashmap of active time containers during the previous
+  // step (SampleTimeContainer) and then test here if the container for this
+  // timed element is in the list.
+  if (!aActiveContainers->GetEntry(timeContainer)) return;
+
+  SMILTime containerTime = timeContainer->GetCurrentTimeAsSMILTime();
+
+  MOZ_ASSERT(!timeContainer->IsSeeking(),
+             "Doing a regular sample but the time container is still seeking");
+  aElement->TimedElement().SampleAt(containerTime);
+}
+
+/*static*/
+void SMILAnimationController::AddAnimationToCompositorTable(
+    SVGAnimationElement* aElement, SMILCompositorTable* aCompositorTable,
+    bool& aStyleFlushNeeded) {
+  // Add a compositor to the hash table if there's not already one there
+  SMILTargetIdentifier key;
+  if (!GetTargetIdentifierForAnimation(aElement, key))
+    // Something's wrong/missing about animation's target; skip this animation
+    return;
+
+  SMILAnimationFunction& func = aElement->AnimationFunction();
+
+  // Only add active animation functions. If there are no active animations
+  // targeting an attribute, no compositor will be created and any previously
+  // applied animations will be cleared.
+  if (func.IsActiveOrFrozen()) {
+    // Look up the compositor for our target, & add our animation function
+    // to its list of animation functions.
+    SMILCompositor* result = aCompositorTable->PutEntry(key);
+    aStyleFlushNeeded |= func.ValueNeedsReparsingEverySample();
+    result->AddAnimationFunction(&func);
+
+  } else if (func.HasChanged()) {
+    // Look up the compositor for our target, and force it to skip the
+    // "nothing's changed so don't bother compositing" optimization for this
+    // sample. |func| is inactive, but it's probably *newly* inactive (since
+    // it's got HasChanged() == true), so we need to make sure to recompose
+    // its target.
+    SMILCompositor* result = aCompositorTable->PutEntry(key);
+    aStyleFlushNeeded |= func.ValueNeedsReparsingEverySample();
+    result->ToggleForceCompositing();
+
+    // We've now made sure that |func|'s inactivity will be reflected as of
+    // this sample. We need to clear its HasChanged() flag so that it won't
+    // trigger this same clause in future samples (until it changes again).
+    func.ClearHasChanged();
+  }
+}
+
+static inline bool IsTransformAttribute(int32_t aNamespaceID,
+                                        nsAtom* aAttributeName) {
+  return aNamespaceID == kNameSpaceID_None &&
+         (aAttributeName == nsGkAtoms::transform ||
+          aAttributeName == nsGkAtoms::patternTransform ||
+          aAttributeName == nsGkAtoms::gradientTransform);
+}
+
+// Helper function that, given a SVGAnimationElement, looks up its target
+// element & target attribute and populates a SMILTargetIdentifier
+// for this target.
+/*static*/
+bool SMILAnimationController::GetTargetIdentifierForAnimation(
+    SVGAnimationElement* aAnimElem, SMILTargetIdentifier& aResult) {
+  // Look up target (animated) element
+  Element* targetElem = aAnimElem->GetTargetElementContent();
+  if (!targetElem)
+    // Animation has no target elem -- skip it.
+    return false;
+
+  // Look up target (animated) attribute
+  // SMILANIM section 3.1, attributeName may
+  // have an XMLNS prefix to indicate the XML namespace.
+  RefPtr<nsAtom> attributeName;
+  int32_t attributeNamespaceID;
+  if (!aAnimElem->GetTargetAttributeName(&attributeNamespaceID,
+                                         getter_AddRefs(attributeName)))
+    // Animation has no target attr -- skip it.
+    return false;
+
+  // animateTransform can only animate transforms, conversely transforms
+  // can only be animated by animateTransform
+  if (IsTransformAttribute(attributeNamespaceID, attributeName) !=
+      (aAnimElem->IsSVGElement(nsGkAtoms::animateTransform)))
+    return false;
+
+  // Construct the key
+  aResult.mElement = targetElem;
+  aResult.mAttributeName = attributeName;
+  aResult.mAttributeNamespaceID = attributeNamespaceID;
+
+  return true;
+}
+
+bool SMILAnimationController::PreTraverse() {
+  return PreTraverseInSubtree(nullptr);
+}
+
+bool SMILAnimationController::PreTraverseInSubtree(Element* aRoot) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!mMightHavePendingStyleUpdates) {
+    return false;
+  }
+
+  nsPresContext* context = mDocument->GetPresContext();
+  if (!context) {
+    return false;
+  }
+
+  bool foundElementsNeedingRestyle = false;
+  for (SVGAnimationElement* animElement : mAnimationElementTable.Keys()) {
+    SMILTargetIdentifier key;
+    if (!GetTargetIdentifierForAnimation(animElement, key)) {
+      // Something's wrong/missing about animation's target; skip this animation
+      continue;
+    }
+
+    // Ignore restyles that aren't in the flattened tree subtree rooted at
+    // aRoot.
+    if (aRoot && !nsContentUtils::ContentIsFlattenedTreeDescendantOf(
+                     key.mElement, aRoot)) {
+      continue;
+    }
+
+    context->RestyleManager()->PostRestyleEventForAnimations(
+        key.mElement, PseudoStyleType::NotPseudo, RestyleHint::RESTYLE_SMIL);
+
+    foundElementsNeedingRestyle = true;
+  }
+
+  // Only clear the mMightHavePendingStyleUpdates flag if we definitely posted
+  // all restyles.
+  if (!aRoot) {
+    mMightHavePendingStyleUpdates = false;
+  }
+
+  return foundElementsNeedingRestyle;
+}
+
+//----------------------------------------------------------------------
+// Add/remove child time containers
+
+nsresult SMILAnimationController::AddChild(SMILTimeContainer& aChild) {
+  const bool wasEmpty = mChildContainerTable.IsEmpty();
+  TimeContainerPtrKey* key = mChildContainerTable.PutEntry(&aChild);
+  NS_ENSURE_TRUE(key, NS_ERROR_OUT_OF_MEMORY);
+  if (wasEmpty) {
+    UpdateSampling();
+  }
+  return NS_OK;
+}
+
+void SMILAnimationController::RemoveChild(SMILTimeContainer& aChild) {
+  mChildContainerTable.RemoveEntry(&aChild);
+  if (mChildContainerTable.IsEmpty()) {
+    UpdateSampling();
+  }
+}
+
+// Helper method
+nsRefreshDriver* SMILAnimationController::GetRefreshDriver() {
+  if (!mDocument) {
+    NS_ERROR("Requesting refresh driver after document has disconnected!");
+    return nullptr;
+  }
+
+  nsPresContext* context = mDocument->GetPresContext();
+  return context ? context->RefreshDriver() : nullptr;
+}
+
+void SMILAnimationController::FlagDocumentNeedsFlush() {
+  if (PresShell* presShell = mDocument->GetPresShell()) {
+    presShell->SetNeedStyleFlush();
+  }
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILAnimationController.h b/dom/smil/SMILAnimationController.h
new file mode 100644
index 0000000000..04f2e34cf3
--- /dev/null
+++ b/dom/smil/SMILAnimationController.h
@@ -0,0 +1,208 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILANIMATIONCONTROLLER_H_
+#define DOM_SMIL_SMILANIMATIONCONTROLLER_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILCompositorTable.h"
+#include "mozilla/SMILMilestone.h"
+#include "mozilla/SMILTimeContainer.h"
+#include "mozilla/UniquePtr.h"
+#include "nsCOMPtr.h"
+#include "nsTArray.h"
+#include "nsTHashtable.h"
+#include "nsHashKeys.h"
+#include "nsRefreshObservers.h"
+
+class nsRefreshDriver;
+
+namespace mozilla {
+struct SMILTargetIdentifier;
+namespace dom {
+class Element;
+class SVGAnimationElement;
+}  // namespace dom
+
+//----------------------------------------------------------------------
+// SMILAnimationController
+//
+// The animation controller maintains the animation timer and determines the
+// sample times and sample rate for all SMIL animations in a document. There is
+// at most one animation controller per document so that frame-rate tuning can
+// be performed at a document-level.
+//
+// The animation controller can contain many child time containers (timed
+// document root objects) which may correspond to SVG document fragments within
+// a compound document. These time containers can be paused individually or
+// here, at the document level.
+//
+class SMILAnimationController final : public SMILTimeContainer,
+                                      public nsARefreshObserver {
+ public:
+  explicit SMILAnimationController(mozilla::dom::Document* aDoc);
+
+  // Clears mDocument pointer. (Called by our mozilla::dom::Document when it's
+  // going away)
+  void Disconnect();
+
+  // SMILContainer
+  void Pause(uint32_t aType) override;
+  void Resume(uint32_t aType) override;
+  SMILTime GetParentTime() const override;
+
+  // nsARefreshObserver
+  NS_IMETHOD_(MozExternalRefCountType) AddRef() override;
+  NS_IMETHOD_(MozExternalRefCountType) Release() override;
+
+  void WillRefresh(mozilla::TimeStamp aTime) override;
+
+  // Methods for registering and enumerating animation elements
+  void RegisterAnimationElement(
+      mozilla::dom::SVGAnimationElement* aAnimationElement);
+  void UnregisterAnimationElement(
+      mozilla::dom::SVGAnimationElement* aAnimationElement);
+
+  // Methods for resampling all animations
+  // (A resample performs the same operations as a sample but doesn't advance
+  // the current time and doesn't check if the container is paused)
+  // This will flush pending style changes for the document.
+  void Resample() { DoSample(false); }
+
+  void SetResampleNeeded() {
+    if (!mRunningSample && !mResampleNeeded) {
+      FlagDocumentNeedsFlush();
+      mResampleNeeded = true;
+    }
+  }
+
+  // This will flush pending style changes for the document.
+  void FlushResampleRequests() {
+    if (!mResampleNeeded) return;
+
+    Resample();
+  }
+
+  // Methods for handling page transitions
+  void OnPageShow();
+  void OnPageHide();
+
+  // Methods for supporting cycle-collection
+  void Traverse(nsCycleCollectionTraversalCallback* aCallback);
+  void Unlink();
+
+  // Methods for relaying the availability of the refresh driver
+  void NotifyRefreshDriverCreated(nsRefreshDriver* aRefreshDriver);
+  void NotifyRefreshDriverDestroying(nsRefreshDriver* aRefreshDriver);
+
+  // Helper to check if we have any animation elements at all
+  bool HasRegisteredAnimations() const {
+    return mAnimationElementTable.Count() != 0;
+  }
+
+  bool MightHavePendingStyleUpdates() const {
+    return mMightHavePendingStyleUpdates;
+  }
+
+  bool PreTraverse();
+  bool PreTraverseInSubtree(mozilla::dom::Element* aRoot);
+
+ protected:
+  ~SMILAnimationController();
+
+  // alias declarations
+  using TimeContainerPtrKey = nsPtrHashKey<SMILTimeContainer>;
+  using TimeContainerHashtable = nsTHashtable<TimeContainerPtrKey>;
+  using AnimationElementPtrKey = nsPtrHashKey<dom::SVGAnimationElement>;
+  using AnimationElementHashtable = nsTHashtable<AnimationElementPtrKey>;
+
+  // Returns mDocument's refresh driver, if it's got one.
+  nsRefreshDriver* GetRefreshDriver();
+
+  // Methods for controlling whether we're sampling
+  void UpdateSampling();
+  bool ShouldSample() const;
+
+  void StopSampling(nsRefreshDriver* aRefreshDriver);
+
+  // Wrapper for StartSampling that defers if no animations are registered.
+  void MaybeStartSampling(nsRefreshDriver* aRefreshDriver);
+
+  // Sample-related callbacks and implementation helpers
+  void DoSample() override;
+  void DoSample(bool aSkipUnchangedContainers);
+
+  void RewindElements();
+
+  void DoMilestoneSamples();
+
+  static void SampleTimedElement(mozilla::dom::SVGAnimationElement* aElement,
+                                 TimeContainerHashtable* aActiveContainers);
+
+  static void AddAnimationToCompositorTable(
+      mozilla::dom::SVGAnimationElement* aElement,
+      SMILCompositorTable* aCompositorTable, bool& aStyleFlushNeeded);
+
+  static bool GetTargetIdentifierForAnimation(
+      mozilla::dom::SVGAnimationElement* aAnimElem,
+      SMILTargetIdentifier& aResult);
+
+  // Methods for adding/removing time containers
+  nsresult AddChild(SMILTimeContainer& aChild) override;
+  void RemoveChild(SMILTimeContainer& aChild) override;
+
+  void FlagDocumentNeedsFlush();
+
+  // Members
+  nsAutoRefCnt mRefCnt;
+  NS_DECL_OWNINGTHREAD
+
+  AnimationElementHashtable mAnimationElementTable;
+  TimeContainerHashtable mChildContainerTable;
+  mozilla::TimeStamp mCurrentSampleTime;
+  mozilla::TimeStamp mStartTime;
+
+  // Average time between samples from the refresh driver. This is used to
+  // detect large unexpected gaps between samples such as can occur when the
+  // computer sleeps. The nature of the SMIL model means that catching up these
+  // large gaps can be expensive as, for example, many events may need to be
+  // dispatched for the intervening time when no samples were received.
+  //
+  // In such cases, we ignore the intervening gap and continue sampling from
+  // when we were expecting the next sample to arrive.
+  //
+  // Note that we only do this for SMIL and not CSS transitions (which doesn't
+  // have so much work to do to catch up) nor scripted animations (which expect
+  // animation time to follow real time).
+  //
+  // This behaviour does not affect pausing (since we're not *expecting* any
+  // samples then) nor seeking (where the SMIL model behaves somewhat
+  // differently such as not dispatching events).
+  SMILTime mAvgTimeBetweenSamples = 0;
+
+  bool mResampleNeeded = false;
+  bool mRunningSample = false;
+
+  // Are we registered with our document's refresh driver?
+  bool mRegisteredWithRefreshDriver = false;
+
+  // Have we updated animated values without adding them to the restyle tracker?
+  bool mMightHavePendingStyleUpdates = false;
+
+  // Store raw ptr to mDocument.  It owns the controller, so controller
+  // shouldn't outlive it
+  mozilla::dom::Document* mDocument;
+
+  // Contains compositors used in our last sample.  We keep this around
+  // so we can detect when an element/attribute used to be animated,
+  // but isn't anymore for some reason. (e.g. if its <animate> element is
+  // removed or retargeted)
+  UniquePtr<SMILCompositorTable> mLastCompositorTable;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILANIMATIONCONTROLLER_H_
diff --git a/dom/smil/SMILAnimationFunction.cpp b/dom/smil/SMILAnimationFunction.cpp
new file mode 100644
index 0000000000..032ebd60c3
--- /dev/null
+++ b/dom/smil/SMILAnimationFunction.cpp
@@ -0,0 +1,993 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILAnimationFunction.h"
+
+#include <math.h>
+
+#include <algorithm>
+#include <utility>
+
+#include "mozilla/DebugOnly.h"
+#include "mozilla/SMILAttr.h"
+#include "mozilla/SMILCSSValueType.h"
+#include "mozilla/SMILNullType.h"
+#include "mozilla/SMILParserUtils.h"
+#include "mozilla/SMILTimedElement.h"
+#include "mozilla/dom/SVGAnimationElement.h"
+#include "nsAttrValueInlines.h"
+#include "nsCOMArray.h"
+#include "nsCOMPtr.h"
+#include "nsContentUtils.h"
+#include "nsGkAtoms.h"
+#include "nsIContent.h"
+#include "nsReadableUtils.h"
+#include "nsString.h"
+
+using namespace mozilla::dom;
+
+namespace mozilla {
+
+//----------------------------------------------------------------------
+// Static members
+
+nsAttrValue::EnumTable SMILAnimationFunction::sAccumulateTable[] = {
+    {"none", false}, {"sum", true}, {nullptr, 0}};
+
+nsAttrValue::EnumTable SMILAnimationFunction::sAdditiveTable[] = {
+    {"replace", false}, {"sum", true}, {nullptr, 0}};
+
+nsAttrValue::EnumTable SMILAnimationFunction::sCalcModeTable[] = {
+    {"linear", CALC_LINEAR},
+    {"discrete", CALC_DISCRETE},
+    {"paced", CALC_PACED},
+    {"spline", CALC_SPLINE},
+    {nullptr, 0}};
+
+// Any negative number should be fine as a sentinel here,
+// because valid distances are non-negative.
+#define COMPUTE_DISTANCE_ERROR (-1)
+
+//----------------------------------------------------------------------
+// Constructors etc.
+
+SMILAnimationFunction::SMILAnimationFunction()
+    : mSampleTime(-1),
+      mRepeatIteration(0),
+      mBeginTime(INT64_MIN),
+      mAnimationElement(nullptr),
+      mErrorFlags(0),
+      mIsActive(false),
+      mIsFrozen(false),
+      mLastValue(false),
+      mHasChanged(true),
+      mValueNeedsReparsingEverySample(false),
+      mPrevSampleWasSingleValueAnimation(false),
+      mWasSkippedInPrevSample(false) {}
+
+void SMILAnimationFunction::SetAnimationElement(
+    SVGAnimationElement* aAnimationElement) {
+  mAnimationElement = aAnimationElement;
+}
+
+bool SMILAnimationFunction::SetAttr(nsAtom* aAttribute, const nsAString& aValue,
+                                    nsAttrValue& aResult,
+                                    nsresult* aParseResult) {
+  // Some elements such as set and discard don't support all possible attributes
+  if (IsDisallowedAttribute(aAttribute)) {
+    aResult.SetTo(aValue);
+    if (aParseResult) {
+      *aParseResult = NS_OK;
+    }
+    return true;
+  }
+
+  bool foundMatch = true;
+  nsresult parseResult = NS_OK;
+
+  // The attributes 'by', 'from', 'to', and 'values' may be parsed differently
+  // depending on the element & attribute we're animating.  So instead of
+  // parsing them now we re-parse them at every sample.
+  if (aAttribute == nsGkAtoms::by || aAttribute == nsGkAtoms::from ||
+      aAttribute == nsGkAtoms::to || aAttribute == nsGkAtoms::values) {
+    // We parse to, from, by, values at sample time.
+    // XXX Need to flag which attribute has changed and then when we parse it at
+    // sample time, report any errors and reset the flag
+    mHasChanged = true;
+    aResult.SetTo(aValue);
+  } else if (aAttribute == nsGkAtoms::accumulate) {
+    parseResult = SetAccumulate(aValue, aResult);
+  } else if (aAttribute == nsGkAtoms::additive) {
+    parseResult = SetAdditive(aValue, aResult);
+  } else if (aAttribute == nsGkAtoms::calcMode) {
+    parseResult = SetCalcMode(aValue, aResult);
+  } else if (aAttribute == nsGkAtoms::keyTimes) {
+    parseResult = SetKeyTimes(aValue, aResult);
+  } else if (aAttribute == nsGkAtoms::keySplines) {
+    parseResult = SetKeySplines(aValue, aResult);
+  } else {
+    foundMatch = false;
+  }
+
+  if (foundMatch && aParseResult) {
+    *aParseResult = parseResult;
+  }
+
+  return foundMatch;
+}
+
+bool SMILAnimationFunction::UnsetAttr(nsAtom* aAttribute) {
+  if (IsDisallowedAttribute(aAttribute)) {
+    return true;
+  }
+
+  bool foundMatch = true;
+
+  if (aAttribute == nsGkAtoms::by || aAttribute == nsGkAtoms::from ||
+      aAttribute == nsGkAtoms::to || aAttribute == nsGkAtoms::values) {
+    mHasChanged = true;
+  } else if (aAttribute == nsGkAtoms::accumulate) {
+    UnsetAccumulate();
+  } else if (aAttribute == nsGkAtoms::additive) {
+    UnsetAdditive();
+  } else if (aAttribute == nsGkAtoms::calcMode) {
+    UnsetCalcMode();
+  } else if (aAttribute == nsGkAtoms::keyTimes) {
+    UnsetKeyTimes();
+  } else if (aAttribute == nsGkAtoms::keySplines) {
+    UnsetKeySplines();
+  } else {
+    foundMatch = false;
+  }
+
+  return foundMatch;
+}
+
+void SMILAnimationFunction::SampleAt(SMILTime aSampleTime,
+                                     const SMILTimeValue& aSimpleDuration,
+                                     uint32_t aRepeatIteration) {
+  // * Update mHasChanged ("Might this sample be different from prev one?")
+  // Were we previously sampling a fill="freeze" final val? (We're not anymore.)
+  mHasChanged |= mLastValue;
+
+  // Are we sampling at a new point in simple duration? And does that matter?
+  mHasChanged |=
+      (mSampleTime != aSampleTime || mSimpleDuration != aSimpleDuration) &&
+      !IsValueFixedForSimpleDuration();
+
+  // Are we on a new repeat and accumulating across repeats?
+  if (!mErrorFlags) {  // (can't call GetAccumulate() if we've had parse errors)
+    mHasChanged |= (mRepeatIteration != aRepeatIteration) && GetAccumulate();
+  }
+
+  mSampleTime = aSampleTime;
+  mSimpleDuration = aSimpleDuration;
+  mRepeatIteration = aRepeatIteration;
+  mLastValue = false;
+}
+
+void SMILAnimationFunction::SampleLastValue(uint32_t aRepeatIteration) {
+  if (!mLastValue || mRepeatIteration != aRepeatIteration) {
+    mHasChanged = true;
+  }
+
+  mRepeatIteration = aRepeatIteration;
+  mLastValue = true;
+}
+
+void SMILAnimationFunction::Activate(SMILTime aBeginTime) {
+  mBeginTime = aBeginTime;
+  mIsActive = true;
+  mIsFrozen = false;
+  mHasChanged = true;
+}
+
+void SMILAnimationFunction::Inactivate(bool aIsFrozen) {
+  mIsActive = false;
+  mIsFrozen = aIsFrozen;
+  mHasChanged = true;
+}
+
+void SMILAnimationFunction::ComposeResult(const SMILAttr& aSMILAttr,
+                                          SMILValue& aResult) {
+  mHasChanged = false;
+  mPrevSampleWasSingleValueAnimation = false;
+  mWasSkippedInPrevSample = false;
+
+  // Skip animations that are inactive or in error
+  if (!IsActiveOrFrozen() || mErrorFlags != 0) return;
+
+  // Get the animation values
+  SMILValueArray values;
+  nsresult rv = GetValues(aSMILAttr, values);
+  if (NS_FAILED(rv)) return;
+
+  // Check that we have the right number of keySplines and keyTimes
+  CheckValueListDependentAttrs(values.Length());
+  if (mErrorFlags != 0) return;
+
+  // If this interval is active, we must have a non-negative mSampleTime
+  MOZ_ASSERT(mSampleTime >= 0 || !mIsActive,
+             "Negative sample time for active animation");
+  MOZ_ASSERT(mSimpleDuration.IsResolved() || mLastValue,
+             "Unresolved simple duration for active or frozen animation");
+
+  // If we want to add but don't have a base value then just fail outright.
+  // This can happen when we skipped getting the base value because there's an
+  // animation function in the sandwich that should replace it but that function
+  // failed unexpectedly.
+  bool isAdditive = IsAdditive();
+  if (isAdditive && aResult.IsNull()) return;
+
+  SMILValue result;
+
+  if (values.Length() == 1 && !IsToAnimation()) {
+    // Single-valued animation
+    result = values[0];
+    mPrevSampleWasSingleValueAnimation = true;
+
+  } else if (mLastValue) {
+    // Sampling last value
+    const SMILValue& last = values.LastElement();
+    result = last;
+
+    // See comment in AccumulateResult: to-animation does not accumulate
+    if (!IsToAnimation() && GetAccumulate() && mRepeatIteration) {
+      // If the target attribute type doesn't support addition Add will
+      // fail leaving result = last
+      result.Add(last, mRepeatIteration);
+    }
+
+  } else {
+    // Interpolation
+    if (NS_FAILED(InterpolateResult(values, result, aResult))) return;
+
+    if (NS_FAILED(AccumulateResult(values, result))) return;
+  }
+
+  // If additive animation isn't required or isn't supported, set the value.
+  if (!isAdditive || NS_FAILED(aResult.SandwichAdd(result))) {
+    aResult = std::move(result);
+  }
+}
+
+int8_t SMILAnimationFunction::CompareTo(
+    const SMILAnimationFunction* aOther) const {
+  NS_ENSURE_TRUE(aOther, 0);
+
+  NS_ASSERTION(aOther != this, "Trying to compare to self");
+
+  // Inactive animations sort first
+  if (!IsActiveOrFrozen() && aOther->IsActiveOrFrozen()) return -1;
+
+  if (IsActiveOrFrozen() && !aOther->IsActiveOrFrozen()) return 1;
+
+  // Sort based on begin time
+  if (mBeginTime != aOther->GetBeginTime())
+    return mBeginTime > aOther->GetBeginTime() ? 1 : -1;
+
+  // Next sort based on syncbase dependencies: the dependent element sorts after
+  // its syncbase
+  const SMILTimedElement& thisTimedElement = mAnimationElement->TimedElement();
+  const SMILTimedElement& otherTimedElement =
+      aOther->mAnimationElement->TimedElement();
+  if (thisTimedElement.IsTimeDependent(otherTimedElement)) return 1;
+  if (otherTimedElement.IsTimeDependent(thisTimedElement)) return -1;
+
+  // Animations that appear later in the document sort after those earlier in
+  // the document
+  MOZ_ASSERT(mAnimationElement != aOther->mAnimationElement,
+             "Two animations cannot have the same animation content element!");
+
+  return (nsContentUtils::PositionIsBefore(mAnimationElement,
+                                           aOther->mAnimationElement))
+             ? -1
+             : 1;
+}
+
+bool SMILAnimationFunction::WillReplace() const {
+  /*
+   * In IsAdditive() we don't consider to-animation to be additive as it is
+   * a special case that is dealt with differently in the compositing method.
+   * Here, however, we return FALSE for to-animation (i.e. it will NOT replace
+   * the underlying value) as it builds on the underlying value.
+   */
+  return !mErrorFlags && !(IsAdditive() || IsToAnimation());
+}
+
+bool SMILAnimationFunction::HasChanged() const {
+  return mHasChanged || mValueNeedsReparsingEverySample;
+}
+
+bool SMILAnimationFunction::UpdateCachedTarget(
+    const SMILTargetIdentifier& aNewTarget) {
+  if (!mLastTarget.Equals(aNewTarget)) {
+    mLastTarget = aNewTarget;
+    return true;
+  }
+  return false;
+}
+
+//----------------------------------------------------------------------
+// Implementation helpers
+
+nsresult SMILAnimationFunction::InterpolateResult(const SMILValueArray& aValues,
+                                                  SMILValue& aResult,
+                                                  SMILValue& aBaseValue) {
+  // Sanity check animation values
+  if ((!IsToAnimation() && aValues.Length() < 2) ||
+      (IsToAnimation() && aValues.Length() != 1)) {
+    NS_ERROR("Unexpected number of values");
+    return NS_ERROR_FAILURE;
+  }
+
+  if (IsToAnimation() && aBaseValue.IsNull()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Get the normalised progress through the simple duration.
+  //
+  // If we have an indefinite simple duration, just set the progress to be
+  // 0 which will give us the expected behaviour of the animation being fixed at
+  // its starting point.
+  double simpleProgress = 0.0;
+
+  if (mSimpleDuration.IsDefinite()) {
+    SMILTime dur = mSimpleDuration.GetMillis();
+
+    MOZ_ASSERT(dur >= 0, "Simple duration should not be negative");
+    MOZ_ASSERT(mSampleTime >= 0, "Sample time should not be negative");
+
+    if (mSampleTime >= dur || mSampleTime < 0) {
+      NS_ERROR("Animation sampled outside interval");
+      return NS_ERROR_FAILURE;
+    }
+
+    if (dur > 0) {
+      simpleProgress = (double)mSampleTime / dur;
+    }  // else leave simpleProgress at 0.0 (e.g. if mSampleTime == dur == 0)
+  }
+
+  nsresult rv = NS_OK;
+  SMILCalcMode calcMode = GetCalcMode();
+
+  // Force discrete calcMode for visibility since StyleAnimationValue will
+  // try to interpolate it using the special clamping behavior defined for
+  // CSS.
+  if (SMILCSSValueType::PropertyFromValue(aValues[0]) ==
+      eCSSProperty_visibility) {
+    calcMode = CALC_DISCRETE;
+  }
+
+  if (calcMode != CALC_DISCRETE) {
+    // Get the normalised progress between adjacent values
+    const SMILValue* from = nullptr;
+    const SMILValue* to = nullptr;
+    // Init to -1 to make sure that if we ever forget to set this, the
+    // MOZ_ASSERT that tests that intervalProgress is in range will fail.
+    double intervalProgress = -1.f;
+    if (IsToAnimation()) {
+      from = &aBaseValue;
+      to = &aValues[0];
+      if (calcMode == CALC_PACED) {
+        // Note: key[Times/Splines/Points] are ignored for calcMode="paced"
+        intervalProgress = simpleProgress;
+      } else {
+        double scaledSimpleProgress =
+            ScaleSimpleProgress(simpleProgress, calcMode);
+        intervalProgress = ScaleIntervalProgress(scaledSimpleProgress, 0);
+      }
+    } else if (calcMode == CALC_PACED) {
+      rv = ComputePacedPosition(aValues, simpleProgress, intervalProgress, from,
+                                to);
+      // Note: If the above call fails, we'll skip the "from->Interpolate"
+      // call below, and we'll drop into the CALC_DISCRETE section
+      // instead. (as the spec says we should, because our failure was
+      // presumably due to the values being non-additive)
+    } else {  // calcMode == CALC_LINEAR or calcMode == CALC_SPLINE
+      double scaledSimpleProgress =
+          ScaleSimpleProgress(simpleProgress, calcMode);
+      uint32_t index =
+          (uint32_t)floor(scaledSimpleProgress * (aValues.Length() - 1));
+      from = &aValues[index];
+      to = &aValues[index + 1];
+      intervalProgress = scaledSimpleProgress * (aValues.Length() - 1) - index;
+      intervalProgress = ScaleIntervalProgress(intervalProgress, index);
+    }
+
+    if (NS_SUCCEEDED(rv)) {
+      MOZ_ASSERT(from, "NULL from-value during interpolation");
+      MOZ_ASSERT(to, "NULL to-value during interpolation");
+      MOZ_ASSERT(0.0f <= intervalProgress && intervalProgress < 1.0f,
+                 "Interval progress should be in the range [0, 1)");
+      rv = from->Interpolate(*to, intervalProgress, aResult);
+    }
+  }
+
+  // Discrete-CalcMode case
+  // Note: If interpolation failed (isn't supported for this type), the SVG
+  // spec says to force discrete mode.
+  if (calcMode == CALC_DISCRETE || NS_FAILED(rv)) {
+    double scaledSimpleProgress =
+        ScaleSimpleProgress(simpleProgress, CALC_DISCRETE);
+
+    // Floating-point errors can mean that, for example, a sample time of 29s in
+    // a 100s duration animation gives us a simple progress of 0.28999999999
+    // instead of the 0.29 we'd expect. Normally this isn't a noticeable
+    // problem, but when we have sudden jumps in animation values (such as is
+    // the case here with discrete animation) we can get unexpected results.
+    //
+    // To counteract this, before we perform a floor() on the animation
+    // progress, we add a tiny fudge factor to push us into the correct interval
+    // in cases where floating-point errors might cause us to fall short.
+    static const double kFloatingPointFudgeFactor = 1.0e-16;
+    if (scaledSimpleProgress + kFloatingPointFudgeFactor <= 1.0) {
+      scaledSimpleProgress += kFloatingPointFudgeFactor;
+    }
+
+    if (IsToAnimation()) {
+      // We don't follow SMIL 3, 12.6.4, where discrete to animations
+      // are the same as <set> animations.  Instead, we treat it as a
+      // discrete animation with two values (the underlying value and
+      // the to="" value), and honor keyTimes="" as well.
+      uint32_t index = (uint32_t)floor(scaledSimpleProgress * 2);
+      aResult = index == 0 ? aBaseValue : aValues[0];
+    } else {
+      uint32_t index = (uint32_t)floor(scaledSimpleProgress * aValues.Length());
+      aResult = aValues[index];
+
+      // For animation of CSS properties, normally when interpolating we perform
+      // a zero-value fixup which means that empty values (values with type
+      // SMILCSSValueType but a null pointer value) are converted into
+      // a suitable zero value based on whatever they're being interpolated
+      // with. For discrete animation, however, since we don't interpolate,
+      // that never happens. In some rare cases, such as discrete non-additive
+      // by-animation, we can arrive here with |aResult| being such an empty
+      // value so we need to manually perform the fixup.
+      //
+      // We could define a generic method for this on SMILValue but its faster
+      // and simpler to just special case SMILCSSValueType.
+      if (aResult.mType == &SMILCSSValueType::sSingleton) {
+        // We have currently only ever encountered this case for the first
+        // value of a by-animation (which has two values) and since we have no
+        // way of testing other cases we just skip them (but assert if we
+        // ever do encounter them so that we can add code to handle them).
+        if (index + 1 >= aValues.Length()) {
+          MOZ_ASSERT(aResult.mU.mPtr, "The last value should not be empty");
+        } else {
+          // Base the type of the zero value on the next element in the series.
+          SMILCSSValueType::FinalizeValue(aResult, aValues[index + 1]);
+        }
+      }
+    }
+    rv = NS_OK;
+  }
+  return rv;
+}
+
+nsresult SMILAnimationFunction::AccumulateResult(const SMILValueArray& aValues,
+                                                 SMILValue& aResult) {
+  if (!IsToAnimation() && GetAccumulate() && mRepeatIteration) {
+    // If the target attribute type doesn't support addition, Add will
+    // fail and we leave aResult untouched.
+    aResult.Add(aValues.LastElement(), mRepeatIteration);
+  }
+
+  return NS_OK;
+}
+
+/*
+ * Given the simple progress for a paced animation, this method:
+ *  - determines which two elements of the values array we're in between
+ *    (returned as aFrom and aTo)
+ *  - determines where we are between them
+ *    (returned as aIntervalProgress)
+ *
+ * Returns NS_OK, or NS_ERROR_FAILURE if our values don't support distance
+ * computation.
+ */
+nsresult SMILAnimationFunction::ComputePacedPosition(
+    const SMILValueArray& aValues, double aSimpleProgress,
+    double& aIntervalProgress, const SMILValue*& aFrom, const SMILValue*& aTo) {
+  NS_ASSERTION(0.0f <= aSimpleProgress && aSimpleProgress < 1.0f,
+               "aSimpleProgress is out of bounds");
+  NS_ASSERTION(GetCalcMode() == CALC_PACED,
+               "Calling paced-specific function, but not in paced mode");
+  MOZ_ASSERT(aValues.Length() >= 2, "Unexpected number of values");
+
+  // Trivial case: If we have just 2 values, then there's only one interval
+  // for us to traverse, and our progress across that interval is the exact
+  // same as our overall progress.
+  if (aValues.Length() == 2) {
+    aIntervalProgress = aSimpleProgress;
+    aFrom = &aValues[0];
+    aTo = &aValues[1];
+    return NS_OK;
+  }
+
+  double totalDistance = ComputePacedTotalDistance(aValues);
+  if (totalDistance == COMPUTE_DISTANCE_ERROR) return NS_ERROR_FAILURE;
+
+  // If we have 0 total distance, then it's unclear where our "paced" position
+  // should be.  We can just fail, which drops us into discrete animation mode.
+  // (That's fine, since our values are apparently indistinguishable anyway.)
+  if (totalDistance == 0.0) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // total distance we should have moved at this point in time.
+  // (called 'remainingDist' due to how it's used in loop below)
+  double remainingDist = aSimpleProgress * totalDistance;
+
+  // Must be satisfied, because totalDistance is a sum of (non-negative)
+  // distances, and aSimpleProgress is non-negative
+  NS_ASSERTION(remainingDist >= 0, "distance values must be non-negative");
+
+  // Find where remainingDist puts us in the list of values
+  // Note: We could optimize this next loop by caching the
+  // interval-distances in an array, but maybe that's excessive.
+  for (uint32_t i = 0; i < aValues.Length() - 1; i++) {
+    // Note: The following assertion is valid because remainingDist should
+    // start out non-negative, and this loop never shaves off more than its
+    // current value.
+    NS_ASSERTION(remainingDist >= 0, "distance values must be non-negative");
+
+    double curIntervalDist;
+
+    DebugOnly<nsresult> rv =
+        aValues[i].ComputeDistance(aValues[i + 1], curIntervalDist);
+    MOZ_ASSERT(NS_SUCCEEDED(rv),
+               "If we got through ComputePacedTotalDistance, we should "
+               "be able to recompute each sub-distance without errors");
+
+    NS_ASSERTION(curIntervalDist >= 0, "distance values must be non-negative");
+    // Clamp distance value at 0, just in case ComputeDistance is evil.
+    curIntervalDist = std::max(curIntervalDist, 0.0);
+
+    if (remainingDist >= curIntervalDist) {
+      remainingDist -= curIntervalDist;
+    } else {
+      // NOTE: If we get here, then curIntervalDist necessarily is not 0. Why?
+      // Because this clause is only hit when remainingDist < curIntervalDist,
+      // and if curIntervalDist were 0, that would mean remainingDist would
+      // have to be < 0.  But that can't happen, because remainingDist (as
+      // a distance) is non-negative by definition.
+      NS_ASSERTION(curIntervalDist != 0,
+                   "We should never get here with this set to 0...");
+
+      // We found the right spot -- an interpolated position between
+      // values i and i+1.
+      aFrom = &aValues[i];
+      aTo = &aValues[i + 1];
+      aIntervalProgress = remainingDist / curIntervalDist;
+      return NS_OK;
+    }
+  }
+
+  MOZ_ASSERT_UNREACHABLE(
+      "shouldn't complete loop & get here -- if we do, "
+      "then aSimpleProgress was probably out of bounds");
+  return NS_ERROR_FAILURE;
+}
+
+/*
+ * Computes the total distance to be travelled by a paced animation.
+ *
+ * Returns the total distance, or returns COMPUTE_DISTANCE_ERROR if
+ * our values don't support distance computation.
+ */
+double SMILAnimationFunction::ComputePacedTotalDistance(
+    const SMILValueArray& aValues) const {
+  NS_ASSERTION(GetCalcMode() == CALC_PACED,
+               "Calling paced-specific function, but not in paced mode");
+
+  double totalDistance = 0.0;
+  for (uint32_t i = 0; i < aValues.Length() - 1; i++) {
+    double tmpDist;
+    nsresult rv = aValues[i].ComputeDistance(aValues[i + 1], tmpDist);
+    if (NS_FAILED(rv)) {
+      return COMPUTE_DISTANCE_ERROR;
+    }
+
+    // Clamp distance value to 0, just in case we have an evil ComputeDistance
+    // implementation somewhere
+    MOZ_ASSERT(tmpDist >= 0.0f, "distance values must be non-negative");
+    tmpDist = std::max(tmpDist, 0.0);
+
+    totalDistance += tmpDist;
+  }
+
+  return totalDistance;
+}
+
+double SMILAnimationFunction::ScaleSimpleProgress(double aProgress,
+                                                  SMILCalcMode aCalcMode) {
+  if (!HasAttr(nsGkAtoms::keyTimes)) return aProgress;
+
+  uint32_t numTimes = mKeyTimes.Length();
+
+  if (numTimes < 2) return aProgress;
+
+  uint32_t i = 0;
+  for (; i < numTimes - 2 && aProgress >= mKeyTimes[i + 1]; ++i) {
+  }
+
+  if (aCalcMode == CALC_DISCRETE) {
+    // discrete calcMode behaviour differs in that each keyTime defines the time
+    // from when the corresponding value is set, and therefore the last value
+    // needn't be 1. So check if we're in the last 'interval', that is, the
+    // space between the final value and 1.0.
+    if (aProgress >= mKeyTimes[i + 1]) {
+      MOZ_ASSERT(i == numTimes - 2,
+                 "aProgress is not in range of the current interval, yet the "
+                 "current interval is not the last bounded interval either.");
+      ++i;
+    }
+    return (double)i / numTimes;
+  }
+
+  double& intervalStart = mKeyTimes[i];
+  double& intervalEnd = mKeyTimes[i + 1];
+
+  double intervalLength = intervalEnd - intervalStart;
+  if (intervalLength <= 0.0) return intervalStart;
+
+  return (i + (aProgress - intervalStart) / intervalLength) /
+         double(numTimes - 1);
+}
+
+double SMILAnimationFunction::ScaleIntervalProgress(double aProgress,
+                                                    uint32_t aIntervalIndex) {
+  if (GetCalcMode() != CALC_SPLINE) return aProgress;
+
+  if (!HasAttr(nsGkAtoms::keySplines)) return aProgress;
+
+  MOZ_ASSERT(aIntervalIndex < mKeySplines.Length(), "Invalid interval index");
+
+  SMILKeySpline const& spline = mKeySplines[aIntervalIndex];
+  return spline.GetSplineValue(aProgress);
+}
+
+bool SMILAnimationFunction::HasAttr(nsAtom* aAttName) const {
+  if (IsDisallowedAttribute(aAttName)) {
+    return false;
+  }
+  return mAnimationElement->HasAttr(aAttName);
+}
+
+const nsAttrValue* SMILAnimationFunction::GetAttr(nsAtom* aAttName) const {
+  if (IsDisallowedAttribute(aAttName)) {
+    return nullptr;
+  }
+  return mAnimationElement->GetParsedAttr(aAttName);
+}
+
+bool SMILAnimationFunction::GetAttr(nsAtom* aAttName,
+                                    nsAString& aResult) const {
+  if (IsDisallowedAttribute(aAttName)) {
+    return false;
+  }
+  return mAnimationElement->GetAttr(aAttName, aResult);
+}
+
+/*
+ * A utility function to make querying an attribute that corresponds to an
+ * SMILValue a little neater.
+ *
+ * @param aAttName    The attribute name (in the global namespace).
+ * @param aSMILAttr   The SMIL attribute to perform the parsing.
+ * @param[out] aResult        The resulting SMILValue.
+ * @param[out] aPreventCachingOfSandwich
+ *                    If |aResult| contains dependencies on its context that
+ *                    should prevent the result of the animation sandwich from
+ *                    being cached and reused in future samples (as reported
+ *                    by SMILAttr::ValueFromString), then this outparam
+ *                    will be set to true. Otherwise it is left unmodified.
+ *
+ * Returns false if a parse error occurred, otherwise returns true.
+ */
+bool SMILAnimationFunction::ParseAttr(nsAtom* aAttName,
+                                      const SMILAttr& aSMILAttr,
+                                      SMILValue& aResult,
+                                      bool& aPreventCachingOfSandwich) const {
+  nsAutoString attValue;
+  if (GetAttr(aAttName, attValue)) {
+    nsresult rv = aSMILAttr.ValueFromString(attValue, mAnimationElement,
+                                            aResult, aPreventCachingOfSandwich);
+    if (NS_FAILED(rv)) return false;
+  }
+  return true;
+}
+
+/*
+ * SMILANIM specifies the following rules for animation function values:
+ *
+ * (1) if values is set, it overrides everything
+ * (2) for from/to/by animation at least to or by must be specified, from on its
+ *     own (or nothing) is an error--which we will ignore
+ * (3) if both by and to are specified only to will be used, by will be ignored
+ * (4) if by is specified without from (by animation), forces additive behaviour
+ * (5) if to is specified without from (to animation), special care needs to be
+ *     taken when compositing animation as such animations are composited last.
+ *
+ * This helper method applies these rules to fill in the values list and to set
+ * some internal state.
+ */
+nsresult SMILAnimationFunction::GetValues(const SMILAttr& aSMILAttr,
+                                          SMILValueArray& aResult) {
+  if (!mAnimationElement) return NS_ERROR_FAILURE;
+
+  mValueNeedsReparsingEverySample = false;
+  SMILValueArray result;
+
+  // If "values" is set, use it
+  if (HasAttr(nsGkAtoms::values)) {
+    nsAutoString attValue;
+    GetAttr(nsGkAtoms::values, attValue);
+    bool preventCachingOfSandwich = false;
+    if (!SMILParserUtils::ParseValues(attValue, mAnimationElement, aSMILAttr,
+                                      result, preventCachingOfSandwich)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    if (preventCachingOfSandwich) {
+      mValueNeedsReparsingEverySample = true;
+    }
+    // Else try to/from/by
+  } else {
+    bool preventCachingOfSandwich = false;
+    bool parseOk = true;
+    SMILValue to, from, by;
+    parseOk &=
+        ParseAttr(nsGkAtoms::to, aSMILAttr, to, preventCachingOfSandwich);
+    parseOk &=
+        ParseAttr(nsGkAtoms::from, aSMILAttr, from, preventCachingOfSandwich);
+    parseOk &=
+        ParseAttr(nsGkAtoms::by, aSMILAttr, by, preventCachingOfSandwich);
+
+    if (preventCachingOfSandwich) {
+      mValueNeedsReparsingEverySample = true;
+    }
+
+    if (!parseOk || !result.SetCapacity(2, fallible)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    // AppendElement() below must succeed, because SetCapacity() succeeded.
+    if (!to.IsNull()) {
+      if (!from.IsNull()) {
+        MOZ_ALWAYS_TRUE(result.AppendElement(from, fallible));
+        MOZ_ALWAYS_TRUE(result.AppendElement(to, fallible));
+      } else {
+        MOZ_ALWAYS_TRUE(result.AppendElement(to, fallible));
+      }
+    } else if (!by.IsNull()) {
+      SMILValue effectiveFrom(by.mType);
+      if (!from.IsNull()) effectiveFrom = from;
+      // Set values to 'from; from + by'
+      MOZ_ALWAYS_TRUE(result.AppendElement(effectiveFrom, fallible));
+      SMILValue effectiveTo(effectiveFrom);
+      if (!effectiveTo.IsNull() && NS_SUCCEEDED(effectiveTo.Add(by))) {
+        MOZ_ALWAYS_TRUE(result.AppendElement(effectiveTo, fallible));
+      } else {
+        // Using by-animation with non-additive type or bad base-value
+        return NS_ERROR_FAILURE;
+      }
+    } else {
+      // No values, no to, no by -- call it a day
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  aResult = std::move(result);
+
+  return NS_OK;
+}
+
+void SMILAnimationFunction::CheckValueListDependentAttrs(uint32_t aNumValues) {
+  CheckKeyTimes(aNumValues);
+  CheckKeySplines(aNumValues);
+}
+
+/**
+ * Performs checks for the keyTimes attribute required by the SMIL spec but
+ * which depend on other attributes and therefore needs to be updated as
+ * dependent attributes are set.
+ */
+void SMILAnimationFunction::CheckKeyTimes(uint32_t aNumValues) {
+  if (!HasAttr(nsGkAtoms::keyTimes)) return;
+
+  SMILCalcMode calcMode = GetCalcMode();
+
+  // attribute is ignored for calcMode = paced
+  if (calcMode == CALC_PACED) {
+    SetKeyTimesErrorFlag(false);
+    return;
+  }
+
+  uint32_t numKeyTimes = mKeyTimes.Length();
+  if (numKeyTimes < 1) {
+    // keyTimes isn't set or failed preliminary checks
+    SetKeyTimesErrorFlag(true);
+    return;
+  }
+
+  // no. keyTimes == no. values
+  // For to-animation the number of values is considered to be 2.
+  bool matchingNumOfValues = numKeyTimes == (IsToAnimation() ? 2 : aNumValues);
+  if (!matchingNumOfValues) {
+    SetKeyTimesErrorFlag(true);
+    return;
+  }
+
+  // first value must be 0
+  if (mKeyTimes[0] != 0.0) {
+    SetKeyTimesErrorFlag(true);
+    return;
+  }
+
+  // last value must be 1 for linear or spline calcModes
+  if (calcMode != CALC_DISCRETE && numKeyTimes > 1 &&
+      mKeyTimes.LastElement() != 1.0) {
+    SetKeyTimesErrorFlag(true);
+    return;
+  }
+
+  SetKeyTimesErrorFlag(false);
+}
+
+void SMILAnimationFunction::CheckKeySplines(uint32_t aNumValues) {
+  // attribute is ignored if calc mode is not spline
+  if (GetCalcMode() != CALC_SPLINE) {
+    SetKeySplinesErrorFlag(false);
+    return;
+  }
+
+  // calc mode is spline but the attribute is not set
+  if (!HasAttr(nsGkAtoms::keySplines)) {
+    SetKeySplinesErrorFlag(false);
+    return;
+  }
+
+  if (mKeySplines.Length() < 1) {
+    // keyTimes isn't set or failed preliminary checks
+    SetKeySplinesErrorFlag(true);
+    return;
+  }
+
+  // ignore splines if there's only one value
+  if (aNumValues == 1 && !IsToAnimation()) {
+    SetKeySplinesErrorFlag(false);
+    return;
+  }
+
+  // no. keySpline specs == no. values - 1
+  uint32_t splineSpecs = mKeySplines.Length();
+  if ((splineSpecs != aNumValues - 1 && !IsToAnimation()) ||
+      (IsToAnimation() && splineSpecs != 1)) {
+    SetKeySplinesErrorFlag(true);
+    return;
+  }
+
+  SetKeySplinesErrorFlag(false);
+}
+
+bool SMILAnimationFunction::IsValueFixedForSimpleDuration() const {
+  return mSimpleDuration.IsIndefinite() ||
+         (!mHasChanged && mPrevSampleWasSingleValueAnimation);
+}
+
+//----------------------------------------------------------------------
+// Property getters
+
+bool SMILAnimationFunction::GetAccumulate() const {
+  const nsAttrValue* value = GetAttr(nsGkAtoms::accumulate);
+  if (!value) return false;
+
+  return value->GetEnumValue();
+}
+
+bool SMILAnimationFunction::GetAdditive() const {
+  const nsAttrValue* value = GetAttr(nsGkAtoms::additive);
+  if (!value) return false;
+
+  return value->GetEnumValue();
+}
+
+SMILAnimationFunction::SMILCalcMode SMILAnimationFunction::GetCalcMode() const {
+  const nsAttrValue* value = GetAttr(nsGkAtoms::calcMode);
+  if (!value) return CALC_LINEAR;
+
+  return SMILCalcMode(value->GetEnumValue());
+}
+
+//----------------------------------------------------------------------
+// Property setters / un-setters:
+
+nsresult SMILAnimationFunction::SetAccumulate(const nsAString& aAccumulate,
+                                              nsAttrValue& aResult) {
+  mHasChanged = true;
+  bool parseResult =
+      aResult.ParseEnumValue(aAccumulate, sAccumulateTable, true);
+  SetAccumulateErrorFlag(!parseResult);
+  return parseResult ? NS_OK : NS_ERROR_FAILURE;
+}
+
+void SMILAnimationFunction::UnsetAccumulate() {
+  SetAccumulateErrorFlag(false);
+  mHasChanged = true;
+}
+
+nsresult SMILAnimationFunction::SetAdditive(const nsAString& aAdditive,
+                                            nsAttrValue& aResult) {
+  mHasChanged = true;
+  bool parseResult = aResult.ParseEnumValue(aAdditive, sAdditiveTable, true);
+  SetAdditiveErrorFlag(!parseResult);
+  return parseResult ? NS_OK : NS_ERROR_FAILURE;
+}
+
+void SMILAnimationFunction::UnsetAdditive() {
+  SetAdditiveErrorFlag(false);
+  mHasChanged = true;
+}
+
+nsresult SMILAnimationFunction::SetCalcMode(const nsAString& aCalcMode,
+                                            nsAttrValue& aResult) {
+  mHasChanged = true;
+  bool parseResult = aResult.ParseEnumValue(aCalcMode, sCalcModeTable, true);
+  SetCalcModeErrorFlag(!parseResult);
+  return parseResult ? NS_OK : NS_ERROR_FAILURE;
+}
+
+void SMILAnimationFunction::UnsetCalcMode() {
+  SetCalcModeErrorFlag(false);
+  mHasChanged = true;
+}
+
+nsresult SMILAnimationFunction::SetKeySplines(const nsAString& aKeySplines,
+                                              nsAttrValue& aResult) {
+  mKeySplines.Clear();
+  aResult.SetTo(aKeySplines);
+
+  mHasChanged = true;
+
+  if (!SMILParserUtils::ParseKeySplines(aKeySplines, mKeySplines)) {
+    mKeySplines.Clear();
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+void SMILAnimationFunction::UnsetKeySplines() {
+  mKeySplines.Clear();
+  SetKeySplinesErrorFlag(false);
+  mHasChanged = true;
+}
+
+nsresult SMILAnimationFunction::SetKeyTimes(const nsAString& aKeyTimes,
+                                            nsAttrValue& aResult) {
+  mKeyTimes.Clear();
+  aResult.SetTo(aKeyTimes);
+
+  mHasChanged = true;
+
+  if (!SMILParserUtils::ParseSemicolonDelimitedProgressList(aKeyTimes, true,
+                                                            mKeyTimes)) {
+    mKeyTimes.Clear();
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+void SMILAnimationFunction::UnsetKeyTimes() {
+  mKeyTimes.Clear();
+  SetKeyTimesErrorFlag(false);
+  mHasChanged = true;
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILAnimationFunction.h b/dom/smil/SMILAnimationFunction.h
new file mode 100644
index 0000000000..8e85da76f6
--- /dev/null
+++ b/dom/smil/SMILAnimationFunction.h
@@ -0,0 +1,444 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILANIMATIONFUNCTION_H_
+#define DOM_SMIL_SMILANIMATIONFUNCTION_H_
+
+#include "mozilla/SMILAttr.h"
+#include "mozilla/SMILKeySpline.h"
+#include "mozilla/SMILTargetIdentifier.h"
+#include "mozilla/SMILTimeValue.h"
+#include "mozilla/SMILTypes.h"
+#include "mozilla/SMILValue.h"
+#include "nsAttrValue.h"
+#include "nsGkAtoms.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+namespace mozilla {
+namespace dom {
+class SVGAnimationElement;
+}  // namespace dom
+
+//----------------------------------------------------------------------
+// SMILAnimationFunction
+//
+// The animation function calculates animation values. It it is provided with
+// time parameters (sample time, repeat iteration etc.) and it uses this to
+// build an appropriate animation value by performing interpolation and
+// addition operations.
+//
+// It is responsible for implementing the animation parameters of an animation
+// element (e.g. from, by, to, values, calcMode, additive, accumulate, keyTimes,
+// keySplines)
+//
+class SMILAnimationFunction {
+ public:
+  SMILAnimationFunction();
+
+  /*
+   * Sets the owning animation element which this class uses to query attribute
+   * values and compare document positions.
+   */
+  void SetAnimationElement(
+      mozilla::dom::SVGAnimationElement* aAnimationElement);
+
+  /*
+   * Sets animation-specific attributes (or marks them dirty, in the case
+   * of from/to/by/values).
+   *
+   * @param aAttribute The attribute being set
+   * @param aValue     The updated value of the attribute.
+   * @param aResult    The nsAttrValue object that may be used for storing the
+   *                   parsed result.
+   * @param aParseResult  Outparam used for reporting parse errors. Will be set
+   *                      to NS_OK if everything succeeds.
+   * @return  true if aAttribute is a recognized animation-related
+   *          attribute; false otherwise.
+   */
+  virtual bool SetAttr(nsAtom* aAttribute, const nsAString& aValue,
+                       nsAttrValue& aResult, nsresult* aParseResult = nullptr);
+
+  /*
+   * Unsets the given attribute.
+   *
+   * @returns true if aAttribute is a recognized animation-related
+   *          attribute; false otherwise.
+   */
+  virtual bool UnsetAttr(nsAtom* aAttribute);
+
+  /**
+   * Indicate a new sample has occurred.
+   *
+   * @param aSampleTime The sample time for this timed element expressed in
+   *                    simple time.
+   * @param aSimpleDuration The simple duration for this timed element.
+   * @param aRepeatIteration  The repeat iteration for this sample. The first
+   *                          iteration has a value of 0.
+   */
+  void SampleAt(SMILTime aSampleTime, const SMILTimeValue& aSimpleDuration,
+                uint32_t aRepeatIteration);
+
+  /**
+   * Indicate to sample using the last value defined for the animation function.
+   * This value is not normally sampled due to the end-point exclusive timing
+   * model but only occurs when the fill mode is "freeze" and the active
+   * duration is an even multiple of the simple duration.
+   *
+   * @param aRepeatIteration  The repeat iteration for this sample. The first
+   *                          iteration has a value of 0.
+   */
+  void SampleLastValue(uint32_t aRepeatIteration);
+
+  /**
+   * Indicate that this animation is now active. This is used to instruct the
+   * animation function that it should now add its result to the animation
+   * sandwich. The begin time is also provided for proper prioritization of
+   * animation functions, and for this reason, this method must be called
+   * before either of the Sample methods.
+   *
+   * @param aBeginTime The begin time for the newly active interval.
+   */
+  void Activate(SMILTime aBeginTime);
+
+  /**
+   * Indicate that this animation is no longer active. This is used to instruct
+   * the animation function that it should no longer add its result to the
+   * animation sandwich.
+   *
+   * @param aIsFrozen true if this animation should continue to contribute
+   *                  to the animation sandwich using the most recent sample
+   *                  parameters.
+   */
+  void Inactivate(bool aIsFrozen);
+
+  /**
+   * Combines the result of this animation function for the last sample with the
+   * specified value.
+   *
+   * @param aSMILAttr This animation's target attribute. Used here for
+   *                  doing attribute-specific parsing of from/to/by/values.
+   *
+   * @param aResult   The value to compose with.
+   */
+  void ComposeResult(const SMILAttr& aSMILAttr, SMILValue& aResult);
+
+  /**
+   * Returns the relative priority of this animation to another. The priority is
+   * used for determining the position of the animation in the animation
+   * sandwich -- higher priority animations are applied on top of lower
+   * priority animations.
+   *
+   * @return  -1 if this animation has lower priority or 1 if this animation has
+   *          higher priority
+   *
+   * This method should never return any other value, including 0.
+   */
+  int8_t CompareTo(const SMILAnimationFunction* aOther) const;
+
+  /*
+   * The following methods are provided so that the compositor can optimize its
+   * operations by only composing those animation that will affect the final
+   * result.
+   */
+
+  /**
+   * Indicates if the animation is currently active or frozen. Inactive
+   * animations will not contribute to the composed result.
+   *
+   * @return  true if the animation is active or frozen, false otherwise.
+   */
+  bool IsActiveOrFrozen() const {
+    /*
+     * - Frozen animations should be considered active for the purposes of
+     * compositing.
+     * - This function does not assume that our SMILValues (by/from/to/values)
+     * have already been parsed.
+     */
+    return (mIsActive || mIsFrozen);
+  }
+
+  /**
+   * Indicates if the animation is active.
+   *
+   * @return  true if the animation is active, false otherwise.
+   */
+  bool IsActive() const { return mIsActive; }
+
+  /**
+   * Indicates if this animation will replace the passed in result rather than
+   * adding to it. Animations that replace the underlying value may be called
+   * without first calling lower priority animations.
+   *
+   * @return  True if the animation will replace, false if it will add or
+   *          otherwise build on the passed in value.
+   */
+  virtual bool WillReplace() const;
+
+  /**
+   * Indicates if the parameters for this animation have changed since the last
+   * time it was composited. This allows rendering to be performed only when
+   * necessary, particularly when no animations are active.
+   *
+   * Note that the caller is responsible for determining if the animation
+   * target has changed (with help from my UpdateCachedTarget() method).
+   *
+   * @return  true if the animation parameters have changed, false
+   *          otherwise.
+   */
+  bool HasChanged() const;
+
+  /**
+   * This method lets us clear the 'HasChanged' flag for inactive animations
+   * after we've reacted to their change to the 'inactive' state, so that we
+   * won't needlessly recompose their targets in every sample.
+   *
+   * This should only be called on an animation function that is inactive and
+   * that returns true from HasChanged().
+   */
+  void ClearHasChanged() {
+    MOZ_ASSERT(HasChanged(),
+               "clearing mHasChanged flag, when it's already false");
+    MOZ_ASSERT(!IsActiveOrFrozen(),
+               "clearing mHasChanged flag for active animation");
+    mHasChanged = false;
+  }
+
+  /**
+   * Updates the cached record of our animation target, and returns a boolean
+   * that indicates whether the target has changed since the last call to this
+   * function. (This lets SMILCompositor check whether its animation
+   * functions have changed value or target since the last sample.  If none of
+   * them have, then the compositor doesn't need to do anything.)
+   *
+   * @param aNewTarget A SMILTargetIdentifier representing the animation
+   *                   target of this function for this sample.
+   * @return  true if |aNewTarget| is different from the old cached value;
+   *          otherwise, false.
+   */
+  bool UpdateCachedTarget(const SMILTargetIdentifier& aNewTarget);
+
+  /**
+   * Returns true if this function was skipped in the previous sample (because
+   * there was a higher-priority non-additive animation). If a skipped animation
+   * function is later used, then the animation sandwich must be recomposited.
+   */
+  bool WasSkippedInPrevSample() const { return mWasSkippedInPrevSample; }
+
+  /**
+   * Mark this animation function as having been skipped. By marking the
+   * function as skipped, if it is used in a subsequent sample we'll know to
+   * recomposite the sandwich.
+   */
+  void SetWasSkipped() { mWasSkippedInPrevSample = true; }
+
+  /**
+   * Returns true if we need to recalculate the animation value on every sample.
+   * (e.g. because it depends on context like the font-size)
+   */
+  bool ValueNeedsReparsingEverySample() const {
+    return mValueNeedsReparsingEverySample;
+  }
+
+  // Comparator utility class, used for sorting SMILAnimationFunctions
+  class Comparator {
+   public:
+    bool Equals(const SMILAnimationFunction* aElem1,
+                const SMILAnimationFunction* aElem2) const {
+      return (aElem1->CompareTo(aElem2) == 0);
+    }
+    bool LessThan(const SMILAnimationFunction* aElem1,
+                  const SMILAnimationFunction* aElem2) const {
+      return (aElem1->CompareTo(aElem2) < 0);
+    }
+  };
+
+ protected:
+  // alias declarations
+  using SMILValueArray = FallibleTArray<SMILValue>;
+
+  // Types
+  enum SMILCalcMode : uint8_t {
+    CALC_LINEAR,
+    CALC_DISCRETE,
+    CALC_PACED,
+    CALC_SPLINE
+  };
+
+  // Used for sorting SMILAnimationFunctions
+  SMILTime GetBeginTime() const { return mBeginTime; }
+
+  // Property getters
+  bool GetAccumulate() const;
+  bool GetAdditive() const;
+  virtual SMILCalcMode GetCalcMode() const;
+
+  // Property setters
+  nsresult SetAccumulate(const nsAString& aAccumulate, nsAttrValue& aResult);
+  nsresult SetAdditive(const nsAString& aAdditive, nsAttrValue& aResult);
+  nsresult SetCalcMode(const nsAString& aCalcMode, nsAttrValue& aResult);
+  nsresult SetKeyTimes(const nsAString& aKeyTimes, nsAttrValue& aResult);
+  nsresult SetKeySplines(const nsAString& aKeySplines, nsAttrValue& aResult);
+
+  // Property un-setters
+  void UnsetAccumulate();
+  void UnsetAdditive();
+  void UnsetCalcMode();
+  void UnsetKeyTimes();
+  void UnsetKeySplines();
+
+  // Helpers
+  virtual bool IsDisallowedAttribute(const nsAtom* aAttribute) const {
+    return false;
+  }
+  virtual nsresult InterpolateResult(const SMILValueArray& aValues,
+                                     SMILValue& aResult, SMILValue& aBaseValue);
+  nsresult AccumulateResult(const SMILValueArray& aValues, SMILValue& aResult);
+
+  nsresult ComputePacedPosition(const SMILValueArray& aValues,
+                                double aSimpleProgress,
+                                double& aIntervalProgress,
+                                const SMILValue*& aFrom, const SMILValue*& aTo);
+  double ComputePacedTotalDistance(const SMILValueArray& aValues) const;
+
+  /**
+   * Adjust the simple progress, that is, the point within the simple duration,
+   * by applying any keyTimes.
+   */
+  double ScaleSimpleProgress(double aProgress, SMILCalcMode aCalcMode);
+  /**
+   * Adjust the progress within an interval, that is, between two animation
+   * values, by applying any keySplines.
+   */
+  double ScaleIntervalProgress(double aProgress, uint32_t aIntervalIndex);
+
+  // Convenience attribute getters
+  bool HasAttr(nsAtom* aAttName) const;
+  const nsAttrValue* GetAttr(nsAtom* aAttName) const;
+  bool GetAttr(nsAtom* aAttName, nsAString& aResult) const;
+
+  bool ParseAttr(nsAtom* aAttName, const SMILAttr& aSMILAttr,
+                 SMILValue& aResult, bool& aPreventCachingOfSandwich) const;
+
+  virtual nsresult GetValues(const SMILAttr& aSMILAttr,
+                             SMILValueArray& aResult);
+
+  virtual void CheckValueListDependentAttrs(uint32_t aNumValues);
+  void CheckKeyTimes(uint32_t aNumValues);
+  void CheckKeySplines(uint32_t aNumValues);
+
+  virtual bool IsToAnimation() const {
+    return !HasAttr(nsGkAtoms::values) && HasAttr(nsGkAtoms::to) &&
+           !HasAttr(nsGkAtoms::from);
+  }
+
+  // Returns true if we know our composited value won't change over the
+  // simple duration of this animation (for a fixed base value).
+  virtual bool IsValueFixedForSimpleDuration() const;
+
+  inline bool IsAdditive() const {
+    /*
+     * Animation is additive if:
+     *
+     * (1) additive = "sum" (GetAdditive() == true), or
+     * (2) it is 'by animation' (by is set, from and values are not)
+     *
+     * Although animation is not additive if it is 'to animation'
+     */
+    bool isByAnimation = (!HasAttr(nsGkAtoms::values) &&
+                          HasAttr(nsGkAtoms::by) && !HasAttr(nsGkAtoms::from));
+    return !IsToAnimation() && (GetAdditive() || isByAnimation);
+  }
+
+  // Setters for error flags
+  // These correspond to bit-indices in mErrorFlags, for tracking parse errors
+  // in these attributes, when those parse errors should block us from doing
+  // animation.
+  enum AnimationAttributeIdx {
+    BF_ACCUMULATE = 0,
+    BF_ADDITIVE = 1,
+    BF_CALC_MODE = 2,
+    BF_KEY_TIMES = 3,
+    BF_KEY_SPLINES = 4,
+    BF_KEY_POINTS = 5  // <animateMotion> only
+  };
+
+  inline void SetAccumulateErrorFlag(bool aNewValue) {
+    SetErrorFlag(BF_ACCUMULATE, aNewValue);
+  }
+  inline void SetAdditiveErrorFlag(bool aNewValue) {
+    SetErrorFlag(BF_ADDITIVE, aNewValue);
+  }
+  inline void SetCalcModeErrorFlag(bool aNewValue) {
+    SetErrorFlag(BF_CALC_MODE, aNewValue);
+  }
+  inline void SetKeyTimesErrorFlag(bool aNewValue) {
+    SetErrorFlag(BF_KEY_TIMES, aNewValue);
+  }
+  inline void SetKeySplinesErrorFlag(bool aNewValue) {
+    SetErrorFlag(BF_KEY_SPLINES, aNewValue);
+  }
+  inline void SetKeyPointsErrorFlag(bool aNewValue) {
+    SetErrorFlag(BF_KEY_POINTS, aNewValue);
+  }
+  inline void SetErrorFlag(AnimationAttributeIdx aField, bool aValue) {
+    if (aValue) {
+      mErrorFlags |= (0x01 << aField);
+    } else {
+      mErrorFlags &= ~(0x01 << aField);
+    }
+  }
+
+  // Members
+  // -------
+
+  static nsAttrValue::EnumTable sAdditiveTable[];
+  static nsAttrValue::EnumTable sCalcModeTable[];
+  static nsAttrValue::EnumTable sAccumulateTable[];
+
+  FallibleTArray<double> mKeyTimes;
+  FallibleTArray<SMILKeySpline> mKeySplines;
+
+  // These are the parameters provided by the previous sample. Currently we
+  // perform lazy calculation. That is, we only calculate the result if and when
+  // instructed by the compositor. This allows us to apply the result directly
+  // to the animation value and allows the compositor to filter out functions
+  // that it determines will not contribute to the final result.
+  SMILTime mSampleTime;  // sample time within simple dur
+  SMILTimeValue mSimpleDuration;
+  uint32_t mRepeatIteration;
+
+  SMILTime mBeginTime;  // document time
+
+  // The owning animation element. This is used for sorting based on document
+  // position and for fetching attribute values stored in the element.
+  // Raw pointer is OK here, because this SMILAnimationFunction can't outlive
+  // its owning animation element.
+  mozilla::dom::SVGAnimationElement* mAnimationElement;
+
+  // Which attributes have been set but have had errors. This is not used for
+  // all attributes but only those which have specified error behaviour
+  // associated with them.
+  uint16_t mErrorFlags;
+
+  // Allows us to check whether an animation function has changed target from
+  // sample to sample (because if neither target nor animated value have
+  // changed, we don't have to do anything).
+  SMILWeakTargetIdentifier mLastTarget;
+
+  // Boolean flags
+  bool mIsActive : 1;
+  bool mIsFrozen : 1;
+  bool mLastValue : 1;
+  bool mHasChanged : 1;
+  bool mValueNeedsReparsingEverySample : 1;
+  bool mPrevSampleWasSingleValueAnimation : 1;
+  bool mWasSkippedInPrevSample : 1;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILANIMATIONFUNCTION_H_
diff --git a/dom/smil/SMILAttr.h b/dom/smil/SMILAttr.h
new file mode 100644
index 0000000000..a67921a9ad
--- /dev/null
+++ b/dom/smil/SMILAttr.h
@@ -0,0 +1,100 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILATTR_H_
+#define DOM_SMIL_SMILATTR_H_
+
+#include "nscore.h"
+#include "nsStringFwd.h"
+
+class nsIContent;
+
+namespace mozilla {
+
+class SMILValue;
+
+namespace dom {
+class SVGAnimationElement;
+}  // namespace dom
+
+////////////////////////////////////////////////////////////////////////
+// SMILAttr: A variable targeted by SMIL for animation and can therefore have
+// an underlying (base) value and an animated value For example, an attribute of
+// a particular SVG element.
+//
+// These objects only exist during the compositing phase of SMIL animation
+// calculations. They have a single owner who is responsible for deleting the
+// object.
+
+class SMILAttr {
+ public:
+  /**
+   * Creates a new SMILValue for this attribute from a string. The string is
+   * parsed in the context of this attribute so that context-dependent values
+   * such as em-based units can be resolved into a canonical form suitable for
+   * animation (including interpolation etc.).
+   *
+   * @param aStr        A string defining the new value to be created.
+   * @param aSrcElement The source animation element. This may be needed to
+   *                    provided additional context data such as for
+   *                    animateTransform where the 'type' attribute is needed to
+   *                    parse the value.
+   * @param[out] aValue Outparam for storing the parsed value.
+   * @param[out] aPreventCachingOfSandwich
+   *                    Outparam to indicate whether the attribute contains
+   *                    dependencies on its context that should prevent the
+   *                    result of the animation sandwich from being cached and
+   *                    reused in future samples.
+   * @return NS_OK on success or an error code if creation failed.
+   */
+  virtual nsresult ValueFromString(
+      const nsAString& aStr,
+      const mozilla::dom::SVGAnimationElement* aSrcElement, SMILValue& aValue,
+      bool& aPreventCachingOfSandwich) const = 0;
+
+  /**
+   * Gets the underlying value of this attribute.
+   *
+   * @return a SMILValue object. returned_object.IsNull() will be true if an
+   * error occurred.
+   */
+  virtual SMILValue GetBaseValue() const = 0;
+
+  /**
+   * Clears the animated value of this attribute.
+   *
+   * NOTE: The animation target is not guaranteed to be in a document when this
+   * method is called. (See bug 523188)
+   */
+  virtual void ClearAnimValue() = 0;
+
+  /**
+   * Sets the presentation value of this attribute.
+   *
+   * @param aValue  The value to set.
+   * @return NS_OK on success or an error code if setting failed.
+   */
+  virtual nsresult SetAnimValue(const SMILValue& aValue) = 0;
+
+  /**
+   * Returns the targeted content node, for any SMILAttr implementations
+   * that want to expose that to the animation logic.  Otherwise, returns
+   * null.
+   *
+   * @return the targeted content node, if this SMILAttr implementation
+   * wishes to make it avaiable.  Otherwise, nullptr.
+   */
+  virtual const nsIContent* GetTargetNode() const { return nullptr; }
+
+  /**
+   * Virtual destructor, to make sure subclasses can clean themselves up.
+   */
+  virtual ~SMILAttr() = default;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILATTR_H_
diff --git a/dom/smil/SMILBoolType.cpp b/dom/smil/SMILBoolType.cpp
new file mode 100644
index 0000000000..218b7af16f
--- /dev/null
+++ b/dom/smil/SMILBoolType.cpp
@@ -0,0 +1,69 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILBoolType.h"
+
+#include "mozilla/SMILValue.h"
+#include "nsDebug.h"
+#include <math.h>
+
+namespace mozilla {
+
+void SMILBoolType::Init(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.IsNull(), "Unexpected value type");
+  aValue.mU.mBool = false;
+  aValue.mType = this;
+}
+
+void SMILBoolType::Destroy(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.mType == this, "Unexpected SMIL value");
+  aValue.mU.mBool = false;
+  aValue.mType = SMILNullType::Singleton();
+}
+
+nsresult SMILBoolType::Assign(SMILValue& aDest, const SMILValue& aSrc) const {
+  MOZ_ASSERT(aDest.mType == aSrc.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aDest.mType == this, "Unexpected SMIL value");
+  aDest.mU.mBool = aSrc.mU.mBool;
+  return NS_OK;
+}
+
+bool SMILBoolType::IsEqual(const SMILValue& aLeft,
+                           const SMILValue& aRight) const {
+  MOZ_ASSERT(aLeft.mType == aRight.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aLeft.mType == this, "Unexpected type for SMIL value");
+
+  return aLeft.mU.mBool == aRight.mU.mBool;
+}
+
+nsresult SMILBoolType::Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+                           uint32_t aCount) const {
+  MOZ_ASSERT(aValueToAdd.mType == aDest.mType, "Trying to add invalid types");
+  MOZ_ASSERT(aValueToAdd.mType == this, "Unexpected source type");
+  return NS_ERROR_FAILURE;  // bool values can't be added to each other
+}
+
+nsresult SMILBoolType::ComputeDistance(const SMILValue& aFrom,
+                                       const SMILValue& aTo,
+                                       double& aDistance) const {
+  MOZ_ASSERT(aFrom.mType == aTo.mType, "Trying to compare different types");
+  MOZ_ASSERT(aFrom.mType == this, "Unexpected source type");
+  return NS_ERROR_FAILURE;  // there is no concept of distance between bool
+                            // values
+}
+
+nsresult SMILBoolType::Interpolate(const SMILValue& aStartVal,
+                                   const SMILValue& aEndVal,
+                                   double aUnitDistance,
+                                   SMILValue& aResult) const {
+  MOZ_ASSERT(aStartVal.mType == aEndVal.mType,
+             "Trying to interpolate different types");
+  MOZ_ASSERT(aStartVal.mType == this, "Unexpected types for interpolation");
+  MOZ_ASSERT(aResult.mType == this, "Unexpected result type");
+  return NS_ERROR_FAILURE;  // bool values do not interpolate
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILBoolType.h b/dom/smil/SMILBoolType.h
new file mode 100644
index 0000000000..a8c12a6860
--- /dev/null
+++ b/dom/smil/SMILBoolType.h
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILBOOLTYPE_H_
+#define DOM_SMIL_SMILBOOLTYPE_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILType.h"
+
+namespace mozilla {
+
+class SMILBoolType : public SMILType {
+ public:
+  // Singleton for SMILValue objects to hold onto.
+  static SMILBoolType* Singleton() {
+    static SMILBoolType sSingleton;
+    return &sSingleton;
+  }
+
+ protected:
+  // SMILType Methods
+  // -------------------
+  void Init(SMILValue& aValue) const override;
+  void Destroy(SMILValue& aValue) const override;
+  nsresult Assign(SMILValue& aDest, const SMILValue& aSrc) const override;
+  nsresult Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+               uint32_t aCount) const override;
+  bool IsEqual(const SMILValue& aLeft, const SMILValue& aRight) const override;
+  nsresult ComputeDistance(const SMILValue& aFrom, const SMILValue& aTo,
+                           double& aDistance) const override;
+  nsresult Interpolate(const SMILValue& aStartVal, const SMILValue& aEndVal,
+                       double aUnitDistance, SMILValue& aResult) const override;
+
+ private:
+  // Private constructor: prevent instances beyond my singleton.
+  constexpr SMILBoolType() = default;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILBOOLTYPE_H_
diff --git a/dom/smil/SMILCSSProperty.cpp b/dom/smil/SMILCSSProperty.cpp
new file mode 100644
index 0000000000..1de2b313c7
--- /dev/null
+++ b/dom/smil/SMILCSSProperty.cpp
@@ -0,0 +1,199 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* representation of a SMIL-animatable CSS property on an element */
+
+#include "SMILCSSProperty.h"
+
+#include <utility>
+
+#include "mozilla/AnimatedPropertyID.h"
+#include "mozilla/SMILCSSValueType.h"
+#include "mozilla/SMILValue.h"
+#include "mozilla/ServoBindings.h"
+#include "mozilla/StyleAnimationValue.h"
+#include "mozilla/dom/Element.h"
+#include "nsCSSProps.h"
+#include "nsDOMCSSAttrDeclaration.h"
+
+namespace mozilla {
+
+// Class Methods
+SMILCSSProperty::SMILCSSProperty(nsCSSPropertyID aPropID,
+                                 dom::Element* aElement,
+                                 const ComputedStyle* aBaseComputedStyle)
+    : mPropID(aPropID),
+      mElement(aElement),
+      mBaseComputedStyle(aBaseComputedStyle) {
+  MOZ_ASSERT(IsPropertyAnimatable(mPropID),
+             "Creating a SMILCSSProperty for a property "
+             "that's not supported for animation");
+}
+
+SMILValue SMILCSSProperty::GetBaseValue() const {
+  // To benefit from Return Value Optimization and avoid copy constructor calls
+  // due to our use of return-by-value, we must return the exact same object
+  // from ALL return points. This function must only return THIS variable:
+  SMILValue baseValue;
+
+  // SPECIAL CASE: (a) Shorthands
+  //               (b) 'display'
+  //               (c) No base ComputedStyle
+  if (nsCSSProps::IsShorthand(mPropID) || mPropID == eCSSProperty_display ||
+      !mBaseComputedStyle) {
+    // We can't look up the base (computed-style) value of shorthand
+    // properties because they aren't guaranteed to have a consistent computed
+    // value.
+    //
+    // Also, although we can look up the base value of the display property,
+    // doing so involves clearing and resetting the property which can cause
+    // frames to be recreated which we'd like to avoid.
+    //
+    // Furthermore, if we don't (yet) have a base ComputedStyle we obviously
+    // can't resolve a base value.
+    //
+    // In any case, just return a dummy value (initialized with the right
+    // type, so as not to indicate failure).
+    SMILValue tmpVal(&SMILCSSValueType::sSingleton);
+    std::swap(baseValue, tmpVal);
+    return baseValue;
+  }
+
+  AnimationValue computedValue;
+  AnimatedPropertyID property(mPropID);
+  MOZ_ASSERT(!property.IsCustom(),
+             "Cannot animate custom properties with SMIL");
+  computedValue.mServo =
+      Servo_ComputedValues_ExtractAnimationValue(mBaseComputedStyle, &property)
+          .Consume();
+  if (!computedValue.mServo) {
+    return baseValue;
+  }
+
+  baseValue = SMILCSSValueType::ValueFromAnimationValue(mPropID, mElement,
+                                                        computedValue);
+  return baseValue;
+}
+
+nsresult SMILCSSProperty::ValueFromString(
+    const nsAString& aStr, const dom::SVGAnimationElement* aSrcElement,
+    SMILValue& aValue, bool& aPreventCachingOfSandwich) const {
+  NS_ENSURE_TRUE(IsPropertyAnimatable(mPropID), NS_ERROR_FAILURE);
+
+  SMILCSSValueType::ValueFromString(mPropID, mElement, aStr, aValue,
+                                    &aPreventCachingOfSandwich);
+
+  if (aValue.IsNull()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // XXX Due to bug 536660 (or at least that seems to be the most likely
+  // culprit), when we have animation setting display:none on a <use> element,
+  // if we DON'T set the property every sample, chaos ensues.
+  if (!aPreventCachingOfSandwich && mPropID == eCSSProperty_display) {
+    aPreventCachingOfSandwich = true;
+  }
+  return NS_OK;
+}
+
+nsresult SMILCSSProperty::SetAnimValue(const SMILValue& aValue) {
+  NS_ENSURE_TRUE(IsPropertyAnimatable(mPropID), NS_ERROR_FAILURE);
+  return mElement->SMILOverrideStyle()->SetSMILValue(mPropID, aValue);
+}
+
+void SMILCSSProperty::ClearAnimValue() {
+  mElement->SMILOverrideStyle()->ClearSMILValue(mPropID);
+}
+
+// Based on http://www.w3.org/TR/SVG/propidx.html
+// static
+bool SMILCSSProperty::IsPropertyAnimatable(nsCSSPropertyID aPropID) {
+  // NOTE: Right now, Gecko doesn't recognize the following properties from
+  // the SVG Property Index:
+  //   alignment-baseline
+  //   baseline-shift
+  //   color-profile
+  //   glyph-orientation-horizontal
+  //   glyph-orientation-vertical
+  //   kerning
+  //   writing-mode
+
+  switch (aPropID) {
+    case eCSSProperty_clip:
+    case eCSSProperty_clip_rule:
+    case eCSSProperty_clip_path:
+    case eCSSProperty_color:
+    case eCSSProperty_color_interpolation:
+    case eCSSProperty_color_interpolation_filters:
+    case eCSSProperty_cursor:
+    case eCSSProperty_display:
+    case eCSSProperty_dominant_baseline:
+    case eCSSProperty_fill:
+    case eCSSProperty_fill_opacity:
+    case eCSSProperty_fill_rule:
+    case eCSSProperty_filter:
+    case eCSSProperty_flood_color:
+    case eCSSProperty_flood_opacity:
+    case eCSSProperty_font:
+    case eCSSProperty_font_family:
+    case eCSSProperty_font_size:
+    case eCSSProperty_font_size_adjust:
+    case eCSSProperty_font_stretch:
+    case eCSSProperty_font_style:
+    case eCSSProperty_font_variant:
+    case eCSSProperty_font_weight:
+    case eCSSProperty_height:
+    case eCSSProperty_image_rendering:
+    case eCSSProperty_letter_spacing:
+    case eCSSProperty_lighting_color:
+    case eCSSProperty_marker:
+    case eCSSProperty_marker_end:
+    case eCSSProperty_marker_mid:
+    case eCSSProperty_marker_start:
+    case eCSSProperty_mask:
+    case eCSSProperty_mask_type:
+    case eCSSProperty_opacity:
+    case eCSSProperty_overflow:
+    case eCSSProperty_pointer_events:
+    case eCSSProperty_shape_rendering:
+    case eCSSProperty_stop_color:
+    case eCSSProperty_stop_opacity:
+    case eCSSProperty_stroke:
+    case eCSSProperty_stroke_dasharray:
+    case eCSSProperty_stroke_dashoffset:
+    case eCSSProperty_stroke_linecap:
+    case eCSSProperty_stroke_linejoin:
+    case eCSSProperty_stroke_miterlimit:
+    case eCSSProperty_stroke_opacity:
+    case eCSSProperty_stroke_width:
+    case eCSSProperty_text_anchor:
+    case eCSSProperty_text_decoration:
+    case eCSSProperty_text_decoration_line:
+    case eCSSProperty_text_rendering:
+    case eCSSProperty_vector_effect:
+    case eCSSProperty_width:
+    case eCSSProperty_visibility:
+    case eCSSProperty_word_spacing:
+      return true;
+
+    // EXPLICITLY NON-ANIMATABLE PROPERTIES:
+    // (Some of these aren't supported at all in Gecko -- I've commented those
+    // ones out. If/when we add support for them, uncomment their line here)
+    // ----------------------------------------------------------------------
+    // case eCSSProperty_enable_background:
+    // case eCSSProperty_glyph_orientation_horizontal:
+    // case eCSSProperty_glyph_orientation_vertical:
+    // case eCSSProperty_writing_mode:
+    case eCSSProperty_direction:
+    case eCSSProperty_unicode_bidi:
+      return false;
+
+    default:
+      return false;
+  }
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILCSSProperty.h b/dom/smil/SMILCSSProperty.h
new file mode 100644
index 0000000000..d83721e56b
--- /dev/null
+++ b/dom/smil/SMILCSSProperty.h
@@ -0,0 +1,80 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* representation of a SMIL-animatable CSS property on an element */
+
+#ifndef DOM_SMIL_SMILCSSPROPERTY_H_
+#define DOM_SMIL_SMILCSSPROPERTY_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILAttr.h"
+#include "nsAtom.h"
+#include "nsCSSPropertyID.h"
+#include "nsCSSValue.h"
+
+namespace mozilla {
+class ComputedStyle;
+namespace dom {
+class Element;
+}  // namespace dom
+
+/**
+ * SMILCSSProperty: Implements the SMILAttr interface for SMIL animations
+ * that target CSS properties.  Represents a particular animation-targeted CSS
+ * property on a particular element.
+ */
+class SMILCSSProperty : public SMILAttr {
+ public:
+  /**
+   * Constructs a new SMILCSSProperty.
+   * @param  aPropID   The CSS property we're interested in animating.
+   * @param  aElement  The element whose CSS property is being animated.
+   * @param  aBaseComputedStyle  The ComputedStyle to use when getting the base
+   *                             value. If this is nullptr and GetBaseValue is
+   *                             called, an empty SMILValue initialized with
+   *                             the SMILCSSValueType will be returned.
+   */
+  SMILCSSProperty(nsCSSPropertyID aPropID, dom::Element* aElement,
+                  const ComputedStyle* aBaseComputedStyle);
+
+  // SMILAttr methods
+  nsresult ValueFromString(const nsAString& aStr,
+                           const dom::SVGAnimationElement* aSrcElement,
+                           SMILValue& aValue,
+                           bool& aPreventCachingOfSandwich) const override;
+  SMILValue GetBaseValue() const override;
+  nsresult SetAnimValue(const SMILValue& aValue) override;
+  void ClearAnimValue() override;
+
+  /**
+   * Utility method - returns true if the given property is supported for
+   * SMIL animation.
+   *
+   * @param   aProperty  The property to check for animation support.
+   * @return  true if the given property is supported for SMIL animation, or
+   *          false otherwise
+   */
+  static bool IsPropertyAnimatable(nsCSSPropertyID aPropID);
+
+ protected:
+  nsCSSPropertyID mPropID;
+  // Using non-refcounted pointer for mElement -- we know mElement will stay
+  // alive for my lifetime because a SMILAttr (like me) only lives as long
+  // as the Compositing step, and DOM elements don't get a chance to die during
+  // that time.
+  dom::Element* mElement;
+
+  // The style to use when fetching base styles.
+  //
+  // As with mElement, since a SMILAttr only lives as long as the
+  // compositing step and since ComposeAttribute holds an owning reference to
+  // the base ComputedStyle, we can use a non-owning reference here.
+  const ComputedStyle* mBaseComputedStyle;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILCSSPROPERTY_H_
diff --git a/dom/smil/SMILCSSValueType.cpp b/dom/smil/SMILCSSValueType.cpp
new file mode 100644
index 0000000000..32f19805a6
--- /dev/null
+++ b/dom/smil/SMILCSSValueType.cpp
@@ -0,0 +1,550 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* representation of a value for a SMIL-animated CSS property */
+
+#include "SMILCSSValueType.h"
+
+#include "nsComputedDOMStyle.h"
+#include "nsColor.h"
+#include "nsCSSProps.h"
+#include "nsCSSValue.h"
+#include "nsDebug.h"
+#include "nsPresContextInlines.h"
+#include "nsPresContext.h"
+#include "nsString.h"
+#include "nsStyleUtil.h"
+#include "mozilla/DeclarationBlock.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/PresShellInlines.h"
+#include "mozilla/ServoBindings.h"
+#include "mozilla/StyleAnimationValue.h"
+#include "mozilla/ServoCSSParser.h"
+#include "mozilla/ServoStyleSet.h"
+#include "mozilla/SMILParserUtils.h"
+#include "mozilla/SMILValue.h"
+#include "mozilla/dom/BaseKeyframeTypesBinding.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/Element.h"
+
+using namespace mozilla::dom;
+
+namespace mozilla {
+
+using ServoAnimationValues = CopyableAutoTArray<RefPtr<StyleAnimationValue>, 1>;
+
+/*static*/
+SMILCSSValueType SMILCSSValueType::sSingleton;
+
+struct ValueWrapper {
+  ValueWrapper(nsCSSPropertyID aPropID, const AnimationValue& aValue)
+      : mPropID(aPropID) {
+    MOZ_ASSERT(!aValue.IsNull());
+    mServoValues.AppendElement(aValue.mServo);
+  }
+  ValueWrapper(nsCSSPropertyID aPropID,
+               const RefPtr<StyleAnimationValue>& aValue)
+      : mPropID(aPropID), mServoValues{(aValue)} {}
+  ValueWrapper(nsCSSPropertyID aPropID, ServoAnimationValues&& aValues)
+      : mPropID(aPropID), mServoValues{std::move(aValues)} {}
+
+  bool operator==(const ValueWrapper& aOther) const {
+    if (mPropID != aOther.mPropID) {
+      return false;
+    }
+
+    MOZ_ASSERT(!mServoValues.IsEmpty());
+    size_t len = mServoValues.Length();
+    if (len != aOther.mServoValues.Length()) {
+      return false;
+    }
+    for (size_t i = 0; i < len; i++) {
+      if (!Servo_AnimationValue_DeepEqual(mServoValues[i],
+                                          aOther.mServoValues[i])) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  bool operator!=(const ValueWrapper& aOther) const {
+    return !(*this == aOther);
+  }
+
+  nsCSSPropertyID mPropID;
+  ServoAnimationValues mServoValues;
+};
+
+// Helper Methods
+// --------------
+
+// If one argument is null, this method updates it to point to "zero"
+// for the other argument's Unit (if applicable; otherwise, we return false).
+//
+// If neither argument is null, this method simply returns true.
+//
+// If both arguments are null, this method returns false.
+//
+// |aZeroValueStorage| should be a reference to a
+// RefPtr<StyleAnimationValue>. This is used where we may need to allocate a
+// new ServoAnimationValue to represent the appropriate zero value.
+//
+// Returns true on success, or otherwise.
+static bool FinalizeServoAnimationValues(
+    const RefPtr<StyleAnimationValue>*& aValue1,
+    const RefPtr<StyleAnimationValue>*& aValue2,
+    RefPtr<StyleAnimationValue>& aZeroValueStorage) {
+  if (!aValue1 && !aValue2) {
+    return false;
+  }
+
+  // Are we missing either val? (If so, it's an implied 0 in other val's units)
+
+  if (!aValue1) {
+    aZeroValueStorage = Servo_AnimationValues_GetZeroValue(*aValue2).Consume();
+    aValue1 = &aZeroValueStorage;
+  } else if (!aValue2) {
+    aZeroValueStorage = Servo_AnimationValues_GetZeroValue(*aValue1).Consume();
+    aValue2 = &aZeroValueStorage;
+  }
+  return *aValue1 && *aValue2;
+}
+
+static ValueWrapper* ExtractValueWrapper(SMILValue& aValue) {
+  return static_cast<ValueWrapper*>(aValue.mU.mPtr);
+}
+
+static const ValueWrapper* ExtractValueWrapper(const SMILValue& aValue) {
+  return static_cast<const ValueWrapper*>(aValue.mU.mPtr);
+}
+
+// Class methods
+// -------------
+void SMILCSSValueType::Init(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.IsNull(), "Unexpected SMIL value type");
+
+  aValue.mU.mPtr = nullptr;
+  aValue.mType = this;
+}
+
+void SMILCSSValueType::Destroy(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.mType == this, "Unexpected SMIL value type");
+  delete static_cast<ValueWrapper*>(aValue.mU.mPtr);
+  aValue.mType = SMILNullType::Singleton();
+}
+
+nsresult SMILCSSValueType::Assign(SMILValue& aDest,
+                                  const SMILValue& aSrc) const {
+  MOZ_ASSERT(aDest.mType == aSrc.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aDest.mType == this, "Unexpected SMIL value type");
+  const ValueWrapper* srcWrapper = ExtractValueWrapper(aSrc);
+  ValueWrapper* destWrapper = ExtractValueWrapper(aDest);
+
+  if (srcWrapper) {
+    if (!destWrapper) {
+      // barely-initialized dest -- need to alloc & copy
+      aDest.mU.mPtr = new ValueWrapper(*srcWrapper);
+    } else {
+      // both already fully-initialized -- just copy straight across
+      *destWrapper = *srcWrapper;
+    }
+  } else if (destWrapper) {
+    // fully-initialized dest, barely-initialized src -- clear dest
+    delete destWrapper;
+    aDest.mU.mPtr = destWrapper = nullptr;
+  }  // else, both are barely-initialized -- nothing to do.
+
+  return NS_OK;
+}
+
+bool SMILCSSValueType::IsEqual(const SMILValue& aLeft,
+                               const SMILValue& aRight) const {
+  MOZ_ASSERT(aLeft.mType == aRight.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aLeft.mType == this, "Unexpected SMIL value");
+  const ValueWrapper* leftWrapper = ExtractValueWrapper(aLeft);
+  const ValueWrapper* rightWrapper = ExtractValueWrapper(aRight);
+
+  if (leftWrapper) {
+    if (rightWrapper) {
+      // Both non-null
+      NS_WARNING_ASSERTION(leftWrapper != rightWrapper,
+                           "Two SMILValues with matching ValueWrapper ptr");
+      return *leftWrapper == *rightWrapper;
+    }
+    // Left non-null, right null
+    return false;
+  }
+  if (rightWrapper) {
+    // Left null, right non-null
+    return false;
+  }
+  // Both null
+  return true;
+}
+
+static bool AddOrAccumulate(SMILValue& aDest, const SMILValue& aValueToAdd,
+                            CompositeOperation aCompositeOp, uint64_t aCount) {
+  MOZ_ASSERT(aValueToAdd.mType == aDest.mType,
+             "Trying to add mismatching types");
+  MOZ_ASSERT(aValueToAdd.mType == &SMILCSSValueType::sSingleton,
+             "Unexpected SMIL value type");
+  MOZ_ASSERT(aCompositeOp == CompositeOperation::Add ||
+                 aCompositeOp == CompositeOperation::Accumulate,
+             "Composite operation should be add or accumulate");
+  MOZ_ASSERT(aCompositeOp != CompositeOperation::Add || aCount == 1,
+             "Count should be 1 if composite operation is add");
+
+  ValueWrapper* destWrapper = ExtractValueWrapper(aDest);
+  const ValueWrapper* valueToAddWrapper = ExtractValueWrapper(aValueToAdd);
+
+  // If both of the values are empty just fail. This can happen in rare cases
+  // such as when the underlying animation produced an empty value.
+  //
+  // Technically, it doesn't matter what we return here since in either case it
+  // will produce the same result: an empty value.
+  if (!destWrapper && !valueToAddWrapper) {
+    return false;
+  }
+
+  nsCSSPropertyID property =
+      valueToAddWrapper ? valueToAddWrapper->mPropID : destWrapper->mPropID;
+  // Special case: font-size-adjust and stroke-dasharray are explicitly
+  // non-additive (even though StyleAnimationValue *could* support adding them)
+  if (property == eCSSProperty_font_size_adjust ||
+      property == eCSSProperty_stroke_dasharray) {
+    return false;
+  }
+  // Skip font shorthand since it includes font-size-adjust.
+  if (property == eCSSProperty_font) {
+    return false;
+  }
+
+  size_t len = valueToAddWrapper ? valueToAddWrapper->mServoValues.Length()
+                                 : destWrapper->mServoValues.Length();
+
+  MOZ_ASSERT(!valueToAddWrapper || !destWrapper ||
+                 valueToAddWrapper->mServoValues.Length() ==
+                     destWrapper->mServoValues.Length(),
+             "Both of values' length in the wrappers should be the same if "
+             "both of them exist");
+
+  for (size_t i = 0; i < len; i++) {
+    const RefPtr<StyleAnimationValue>* valueToAdd =
+        valueToAddWrapper ? &valueToAddWrapper->mServoValues[i] : nullptr;
+    const RefPtr<StyleAnimationValue>* destValue =
+        destWrapper ? &destWrapper->mServoValues[i] : nullptr;
+    RefPtr<StyleAnimationValue> zeroValueStorage;
+    if (!FinalizeServoAnimationValues(valueToAdd, destValue,
+                                      zeroValueStorage)) {
+      return false;
+    }
+
+    // FinalizeServoAnimationValues may have updated destValue so we should make
+    // sure the aDest and aDestWrapper outparams are up-to-date.
+    if (destWrapper) {
+      destWrapper->mServoValues[i] = *destValue;
+    } else {
+      // aDest may be a barely-initialized "zero" destination.
+      aDest.mU.mPtr = destWrapper = new ValueWrapper(property, *destValue);
+      destWrapper->mServoValues.SetLength(len);
+    }
+
+    RefPtr<StyleAnimationValue> result;
+    if (aCompositeOp == CompositeOperation::Add) {
+      result = Servo_AnimationValues_Add(*destValue, *valueToAdd).Consume();
+    } else {
+      result = Servo_AnimationValues_Accumulate(*destValue, *valueToAdd, aCount)
+                   .Consume();
+    }
+
+    if (!result) {
+      return false;
+    }
+    destWrapper->mServoValues[i] = result;
+  }
+
+  return true;
+}
+
+nsresult SMILCSSValueType::SandwichAdd(SMILValue& aDest,
+                                       const SMILValue& aValueToAdd) const {
+  return AddOrAccumulate(aDest, aValueToAdd, CompositeOperation::Add, 1)
+             ? NS_OK
+             : NS_ERROR_FAILURE;
+}
+
+nsresult SMILCSSValueType::Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+                               uint32_t aCount) const {
+  return AddOrAccumulate(aDest, aValueToAdd, CompositeOperation::Accumulate,
+                         aCount)
+             ? NS_OK
+             : NS_ERROR_FAILURE;
+}
+
+nsresult SMILCSSValueType::ComputeDistance(const SMILValue& aFrom,
+                                           const SMILValue& aTo,
+                                           double& aDistance) const {
+  MOZ_ASSERT(aFrom.mType == aTo.mType, "Trying to compare different types");
+  MOZ_ASSERT(aFrom.mType == this, "Unexpected source type");
+
+  const ValueWrapper* fromWrapper = ExtractValueWrapper(aFrom);
+  const ValueWrapper* toWrapper = ExtractValueWrapper(aTo);
+  MOZ_ASSERT(toWrapper, "expecting non-null endpoint");
+
+  size_t len = toWrapper->mServoValues.Length();
+  MOZ_ASSERT(!fromWrapper || fromWrapper->mServoValues.Length() == len,
+             "From and to values length should be the same if "
+             "The start value exists");
+
+  double squareDistance = 0;
+
+  for (size_t i = 0; i < len; i++) {
+    const RefPtr<StyleAnimationValue>* fromValue =
+        fromWrapper ? &fromWrapper->mServoValues[i] : nullptr;
+    const RefPtr<StyleAnimationValue>* toValue = &toWrapper->mServoValues[i];
+    RefPtr<StyleAnimationValue> zeroValueStorage;
+    if (!FinalizeServoAnimationValues(fromValue, toValue, zeroValueStorage)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    double distance =
+        Servo_AnimationValues_ComputeDistance(*fromValue, *toValue);
+    if (distance < 0.0) {
+      return NS_ERROR_FAILURE;
+    }
+
+    if (len == 1) {
+      aDistance = distance;
+      return NS_OK;
+    }
+    squareDistance += distance * distance;
+  }
+
+  aDistance = sqrt(squareDistance);
+
+  return NS_OK;
+}
+
+nsresult SMILCSSValueType::Interpolate(const SMILValue& aStartVal,
+                                       const SMILValue& aEndVal,
+                                       double aUnitDistance,
+                                       SMILValue& aResult) const {
+  MOZ_ASSERT(aStartVal.mType == aEndVal.mType,
+             "Trying to interpolate different types");
+  MOZ_ASSERT(aStartVal.mType == this, "Unexpected types for interpolation");
+  MOZ_ASSERT(aResult.mType == this, "Unexpected result type");
+  MOZ_ASSERT(aUnitDistance >= 0.0 && aUnitDistance <= 1.0,
+             "unit distance value out of bounds");
+  MOZ_ASSERT(!aResult.mU.mPtr, "expecting barely-initialized outparam");
+
+  const ValueWrapper* startWrapper = ExtractValueWrapper(aStartVal);
+  const ValueWrapper* endWrapper = ExtractValueWrapper(aEndVal);
+  MOZ_ASSERT(endWrapper, "expecting non-null endpoint");
+
+  // For discretely-animated properties Servo_AnimationValues_Interpolate will
+  // perform the discrete animation (i.e. 50% flip) and return a success result.
+  // However, SMIL has its own special discrete animation behavior that it uses
+  // when keyTimes are specified, but we won't run that unless that this method
+  // returns a failure to indicate that the property cannot be smoothly
+  // interpolated, i.e. that we need to use a discrete calcMode.
+  //
+  // For shorthands, Servo_Property_IsDiscreteAnimatable will always return
+  // false. That's fine since most shorthands (like 'font' and
+  // 'text-decoration') include non-discrete components. If authors want to
+  // treat all components as discrete then they should use calcMode="discrete".
+  if (Servo_Property_IsDiscreteAnimatable(endWrapper->mPropID)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  ServoAnimationValues results;
+  size_t len = endWrapper->mServoValues.Length();
+  results.SetCapacity(len);
+  MOZ_ASSERT(!startWrapper || startWrapper->mServoValues.Length() == len,
+             "Start and end values length should be the same if "
+             "the start value exists");
+  for (size_t i = 0; i < len; i++) {
+    const RefPtr<StyleAnimationValue>* startValue =
+        startWrapper ? &startWrapper->mServoValues[i] : nullptr;
+    const RefPtr<StyleAnimationValue>* endValue = &endWrapper->mServoValues[i];
+    RefPtr<StyleAnimationValue> zeroValueStorage;
+    if (!FinalizeServoAnimationValues(startValue, endValue, zeroValueStorage)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    RefPtr<StyleAnimationValue> result =
+        Servo_AnimationValues_Interpolate(*startValue, *endValue, aUnitDistance)
+            .Consume();
+    if (!result) {
+      return NS_ERROR_FAILURE;
+    }
+    results.AppendElement(result);
+  }
+  aResult.mU.mPtr = new ValueWrapper(endWrapper->mPropID, std::move(results));
+
+  return NS_OK;
+}
+
+static ServoAnimationValues ValueFromStringHelper(
+    nsCSSPropertyID aPropID, Element* aTargetElement,
+    nsPresContext* aPresContext, const ComputedStyle* aComputedStyle,
+    const nsAString& aString) {
+  ServoAnimationValues result;
+
+  Document* doc = aTargetElement->GetComposedDoc();
+  if (!doc) {
+    return result;
+  }
+
+  // Parse property
+  ServoCSSParser::ParsingEnvironment env =
+      ServoCSSParser::GetParsingEnvironment(doc);
+  RefPtr<StyleLockedDeclarationBlock> servoDeclarationBlock =
+      ServoCSSParser::ParseProperty(
+          aPropID, NS_ConvertUTF16toUTF8(aString), env,
+          StyleParsingMode::ALLOW_UNITLESS_LENGTH |
+              StyleParsingMode::ALLOW_ALL_NUMERIC_VALUES);
+  if (!servoDeclarationBlock) {
+    return result;
+  }
+
+  // Compute value
+  aPresContext->StyleSet()->GetAnimationValues(
+      servoDeclarationBlock, aTargetElement, aComputedStyle, result);
+
+  return result;
+}
+
+// static
+void SMILCSSValueType::ValueFromString(nsCSSPropertyID aPropID,
+                                       Element* aTargetElement,
+                                       const nsAString& aString,
+                                       SMILValue& aValue,
+                                       bool* aIsContextSensitive) {
+  MOZ_ASSERT(aValue.IsNull(), "Outparam should be null-typed");
+  nsPresContext* presContext =
+      nsContentUtils::GetContextForContent(aTargetElement);
+  if (!presContext) {
+    NS_WARNING("Not parsing animation value; unable to get PresContext");
+    return;
+  }
+
+  Document* doc = aTargetElement->GetComposedDoc();
+  if (doc && !nsStyleUtil::CSPAllowsInlineStyle(nullptr, doc, nullptr, 0, 1,
+                                                aString, nullptr)) {
+    return;
+  }
+
+  RefPtr<const ComputedStyle> computedStyle =
+      nsComputedDOMStyle::GetComputedStyle(aTargetElement);
+  if (!computedStyle) {
+    return;
+  }
+
+  ServoAnimationValues parsedValues = ValueFromStringHelper(
+      aPropID, aTargetElement, presContext, computedStyle, aString);
+  if (aIsContextSensitive) {
+    // FIXME: Bug 1358955 - detect context-sensitive values and set this value
+    // appropriately.
+    *aIsContextSensitive = false;
+  }
+
+  if (!parsedValues.IsEmpty()) {
+    sSingleton.Init(aValue);
+    aValue.mU.mPtr = new ValueWrapper(aPropID, std::move(parsedValues));
+  }
+}
+
+// static
+SMILValue SMILCSSValueType::ValueFromAnimationValue(
+    nsCSSPropertyID aPropID, Element* aTargetElement,
+    const AnimationValue& aValue) {
+  SMILValue result;
+
+  Document* doc = aTargetElement->GetComposedDoc();
+  // We'd like to avoid serializing |aValue| if possible, and since the
+  // string passed to CSPAllowsInlineStyle is only used for reporting violations
+  // and an intermediate CSS value is not likely to be particularly useful
+  // in that case, we just use a generic placeholder string instead.
+  static const nsLiteralString kPlaceholderText = u"[SVG animation of CSS]"_ns;
+  if (doc && !nsStyleUtil::CSPAllowsInlineStyle(nullptr, doc, nullptr, 0, 1,
+                                                kPlaceholderText, nullptr)) {
+    return result;
+  }
+
+  sSingleton.Init(result);
+  result.mU.mPtr = new ValueWrapper(aPropID, aValue);
+
+  return result;
+}
+
+// static
+bool SMILCSSValueType::SetPropertyValues(const SMILValue& aValue,
+                                         DeclarationBlock& aDecl) {
+  MOZ_ASSERT(aValue.mType == &SMILCSSValueType::sSingleton,
+             "Unexpected SMIL value type");
+  const ValueWrapper* wrapper = ExtractValueWrapper(aValue);
+  if (!wrapper) {
+    return false;
+  }
+
+  bool changed = false;
+  for (const auto& value : wrapper->mServoValues) {
+    changed |= Servo_DeclarationBlock_SetPropertyToAnimationValue(aDecl.Raw(),
+                                                                  value, {});
+  }
+
+  return changed;
+}
+
+// static
+nsCSSPropertyID SMILCSSValueType::PropertyFromValue(const SMILValue& aValue) {
+  if (aValue.mType != &SMILCSSValueType::sSingleton) {
+    return eCSSProperty_UNKNOWN;
+  }
+
+  const ValueWrapper* wrapper = ExtractValueWrapper(aValue);
+  if (!wrapper) {
+    return eCSSProperty_UNKNOWN;
+  }
+
+  return wrapper->mPropID;
+}
+
+// static
+void SMILCSSValueType::FinalizeValue(SMILValue& aValue,
+                                     const SMILValue& aValueToMatch) {
+  MOZ_ASSERT(aValue.mType == aValueToMatch.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aValue.mType == &SMILCSSValueType::sSingleton,
+             "Unexpected SMIL value type");
+
+  ValueWrapper* valueWrapper = ExtractValueWrapper(aValue);
+  // If |aValue| already has a value, there's nothing to do here.
+  if (valueWrapper) {
+    return;
+  }
+
+  const ValueWrapper* valueToMatchWrapper = ExtractValueWrapper(aValueToMatch);
+  if (!valueToMatchWrapper) {
+    MOZ_ASSERT_UNREACHABLE("Value to match is empty");
+    return;
+  }
+
+  ServoAnimationValues zeroValues;
+  zeroValues.SetCapacity(valueToMatchWrapper->mServoValues.Length());
+
+  for (const auto& valueToMatch : valueToMatchWrapper->mServoValues) {
+    RefPtr<StyleAnimationValue> zeroValue =
+        Servo_AnimationValues_GetZeroValue(valueToMatch).Consume();
+    if (!zeroValue) {
+      return;
+    }
+    zeroValues.AppendElement(std::move(zeroValue));
+  }
+  aValue.mU.mPtr =
+      new ValueWrapper(valueToMatchWrapper->mPropID, std::move(zeroValues));
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILCSSValueType.h b/dom/smil/SMILCSSValueType.h
new file mode 100644
index 0000000000..72c66bdc43
--- /dev/null
+++ b/dom/smil/SMILCSSValueType.h
@@ -0,0 +1,133 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* representation of a value for a SMIL-animated CSS property */
+
+#ifndef DOM_SMIL_SMILCSSVALUETYPE_H_
+#define DOM_SMIL_SMILCSSVALUETYPE_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILType.h"
+#include "nsCSSPropertyID.h"
+#include "nsStringFwd.h"
+
+namespace mozilla {
+struct AnimationValue;
+class DeclarationBlock;
+namespace dom {
+class Element;
+}  // namespace dom
+
+/*
+ * SMILCSSValueType: Represents a SMIL-animated CSS value.
+ */
+class SMILCSSValueType : public SMILType {
+ public:
+  // Singleton for SMILValue objects to hold onto.
+  static SMILCSSValueType sSingleton;
+
+ protected:
+  // SMILType Methods
+  // -------------------
+  void Init(SMILValue& aValue) const override;
+  void Destroy(SMILValue&) const override;
+  nsresult Assign(SMILValue& aDest, const SMILValue& aSrc) const override;
+  bool IsEqual(const SMILValue& aLeft, const SMILValue& aRight) const override;
+  nsresult Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+               uint32_t aCount) const override;
+  nsresult SandwichAdd(SMILValue& aDest,
+                       const SMILValue& aValueToAdd) const override;
+  nsresult ComputeDistance(const SMILValue& aFrom, const SMILValue& aTo,
+                           double& aDistance) const override;
+  nsresult Interpolate(const SMILValue& aStartVal, const SMILValue& aEndVal,
+                       double aUnitDistance, SMILValue& aResult) const override;
+
+ public:
+  // Helper Methods
+  // --------------
+  /**
+   * Sets up the given SMILValue to represent the given string value.  The
+   * string is interpreted as a value for the given property on the given
+   * element.
+   *
+   * On failure, this method leaves aValue.mType == SMILNullType::sSingleton.
+   * Otherwise, this method leaves aValue.mType == this class's singleton.
+   *
+   * @param       aPropID         The property for which we're parsing a value.
+   * @param       aTargetElement  The target element to whom the property/value
+   *                              setting applies.
+   * @param       aString         The string to be parsed as a CSS value.
+   * @param [out] aValue          The SMILValue to be populated. Should
+   *                              initially be null-typed.
+   * @param [out] aIsContextSensitive Set to true if |aString| may produce
+   *                                  a different |aValue| depending on other
+   *                                  CSS properties on |aTargetElement|
+   *                                  or its ancestors (e.g. 'inherit).
+   *                                  false otherwise. May be nullptr.
+   *                                  Not set if the method fails.
+   * @pre  aValue.IsNull()
+   * @post aValue.IsNull() || aValue.mType == SMILCSSValueType::sSingleton
+   */
+  static void ValueFromString(nsCSSPropertyID aPropID,
+                              dom::Element* aTargetElement,
+                              const nsAString& aString, SMILValue& aValue,
+                              bool* aIsContextSensitive);
+
+  /**
+   * Creates a SMILValue to wrap the given animation value.
+   *
+   * @param aPropID         The property that |aValue| corresponds to.
+   * @param aTargetElement  The target element to which the animation value
+   *                        applies.
+   * @param aValue          The animation value to use.
+   * @return                A new SMILValue. On failure, returns a
+   *                        SMILValue with the null type (i.e. rv.IsNull()
+   *                        returns true).
+   */
+  static SMILValue ValueFromAnimationValue(nsCSSPropertyID aPropID,
+                                           dom::Element* aTargetElement,
+                                           const AnimationValue& aValue);
+
+  /**
+   * Sets the relevant property values in the declaration block.
+   *
+   * Returns whether the declaration changed.
+   */
+  static bool SetPropertyValues(const SMILValue&, mozilla::DeclarationBlock&);
+
+  /**
+   * Return the CSS property animated by the specified value.
+   *
+   * @param   aValue   The SMILValue to examine.
+   * @return           The nsCSSPropertyID enum value of the property animated
+   *                   by |aValue|, or eCSSProperty_UNKNOWN if the type of
+   *                   |aValue| is not SMILCSSValueType.
+   */
+  static nsCSSPropertyID PropertyFromValue(const SMILValue& aValue);
+
+  /**
+   * If |aValue| is an empty value, converts it to a suitable zero value by
+   * matching the type of value stored in |aValueToMatch|.
+   *
+   * There is no indication if this method fails. If a suitable zero value could
+   * not be created, |aValue| is simply unmodified.
+   *
+   * @param aValue        The SMILValue (of type SMILCSSValueType) to
+   *                      possibly update.
+   * @param aValueToMatch A SMILValue (of type SMILCSSValueType) for which
+   *                      a corresponding zero value will be created if |aValue|
+   *                      is empty.
+   */
+  static void FinalizeValue(SMILValue& aValue, const SMILValue& aValueToMatch);
+
+ private:
+  // Private constructor: prevent instances beyond my singleton.
+  constexpr SMILCSSValueType() = default;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILCSSVALUETYPE_H_
diff --git a/dom/smil/SMILCompositor.cpp b/dom/smil/SMILCompositor.cpp
new file mode 100644
index 0000000000..6b55267cae
--- /dev/null
+++ b/dom/smil/SMILCompositor.cpp
@@ -0,0 +1,239 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILCompositor.h"
+
+#include "mozilla/dom/SVGSVGElement.h"
+#include "nsComputedDOMStyle.h"
+#include "nsCSSProps.h"
+#include "nsHashKeys.h"
+#include "SMILCSSProperty.h"
+
+namespace mozilla {
+
+// PLDHashEntryHdr methods
+bool SMILCompositor::KeyEquals(KeyTypePointer aKey) const {
+  return aKey && aKey->Equals(mKey);
+}
+
+/*static*/
+PLDHashNumber SMILCompositor::HashKey(KeyTypePointer aKey) {
+  // Combine the 3 values into one numeric value, which will be hashed.
+  // NOTE: We right-shift one of the pointers by 2 to get some randomness in
+  // its 2 lowest-order bits. (Those shifted-off bits will always be 0 since
+  // our pointers will be word-aligned.)
+  return (NS_PTR_TO_UINT32(aKey->mElement.get()) >> 2) +
+         NS_PTR_TO_UINT32(aKey->mAttributeName.get());
+}
+
+// Cycle-collection support
+void SMILCompositor::Traverse(nsCycleCollectionTraversalCallback* aCallback) {
+  if (!mKey.mElement) return;
+
+  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(*aCallback, "Compositor mKey.mElement");
+  aCallback->NoteXPCOMChild(mKey.mElement);
+}
+
+// Other methods
+void SMILCompositor::AddAnimationFunction(SMILAnimationFunction* aFunc) {
+  if (aFunc) {
+    mAnimationFunctions.AppendElement(aFunc);
+  }
+}
+
+void SMILCompositor::ComposeAttribute(bool& aMightHavePendingStyleUpdates) {
+  if (!mKey.mElement) return;
+
+  // If we might need to resolve base styles, grab a suitable ComputedStyle
+  // for initializing our SMILAttr with.
+  RefPtr<const ComputedStyle> baseComputedStyle;
+  if (MightNeedBaseStyle()) {
+    baseComputedStyle = nsComputedDOMStyle::GetUnanimatedComputedStyleNoFlush(
+        mKey.mElement, PseudoStyleType::NotPseudo);
+  }
+
+  // FIRST: Get the SMILAttr (to grab base value from, and to eventually
+  // give animated value to)
+  UniquePtr<SMILAttr> smilAttr = CreateSMILAttr(baseComputedStyle);
+  if (!smilAttr) {
+    // Target attribute not found (or, out of memory)
+    return;
+  }
+  if (mAnimationFunctions.IsEmpty()) {
+    // No active animation functions. (We can still have a SMILCompositor in
+    // that case if an animation function has *just* become inactive)
+    smilAttr->ClearAnimValue();
+    // Removing the animation effect may require a style update.
+    aMightHavePendingStyleUpdates = true;
+    return;
+  }
+
+  // SECOND: Sort the animationFunctions, to prepare for compositing.
+  SMILAnimationFunction::Comparator comparator;
+  mAnimationFunctions.Sort(comparator);
+
+  // THIRD: Step backwards through animation functions to find out
+  // which ones we actually care about.
+  uint32_t firstFuncToCompose = GetFirstFuncToAffectSandwich();
+
+  // FOURTH: Get & cache base value
+  SMILValue sandwichResultValue;
+  if (!mAnimationFunctions[firstFuncToCompose]->WillReplace()) {
+    sandwichResultValue = smilAttr->GetBaseValue();
+  }
+  UpdateCachedBaseValue(sandwichResultValue);
+
+  if (!mForceCompositing) {
+    return;
+  }
+
+  // FIFTH: Compose animation functions
+  aMightHavePendingStyleUpdates = true;
+  uint32_t length = mAnimationFunctions.Length();
+  for (uint32_t i = firstFuncToCompose; i < length; ++i) {
+    mAnimationFunctions[i]->ComposeResult(*smilAttr, sandwichResultValue);
+  }
+  if (sandwichResultValue.IsNull()) {
+    smilAttr->ClearAnimValue();
+    return;
+  }
+
+  // SIXTH: Set the animated value to the final composited result.
+  nsresult rv = smilAttr->SetAnimValue(sandwichResultValue);
+  if (NS_FAILED(rv)) {
+    NS_WARNING("SMILAttr::SetAnimValue failed");
+  }
+}
+
+void SMILCompositor::ClearAnimationEffects() {
+  if (!mKey.mElement || !mKey.mAttributeName) return;
+
+  UniquePtr<SMILAttr> smilAttr = CreateSMILAttr(nullptr);
+  if (!smilAttr) {
+    // Target attribute not found (or, out of memory)
+    return;
+  }
+  smilAttr->ClearAnimValue();
+}
+
+// Protected Helper Functions
+// --------------------------
+UniquePtr<SMILAttr> SMILCompositor::CreateSMILAttr(
+    const ComputedStyle* aBaseComputedStyle) {
+  nsCSSPropertyID propID = GetCSSPropertyToAnimate();
+
+  if (propID != eCSSProperty_UNKNOWN) {
+    return MakeUnique<SMILCSSProperty>(propID, mKey.mElement.get(),
+                                       aBaseComputedStyle);
+  }
+
+  return mKey.mElement->GetAnimatedAttr(mKey.mAttributeNamespaceID,
+                                        mKey.mAttributeName);
+}
+
+nsCSSPropertyID SMILCompositor::GetCSSPropertyToAnimate() const {
+  if (mKey.mAttributeNamespaceID != kNameSpaceID_None) {
+    return eCSSProperty_UNKNOWN;
+  }
+
+  nsCSSPropertyID propID =
+      nsCSSProps::LookupProperty(nsAtomCString(mKey.mAttributeName));
+
+  if (!SMILCSSProperty::IsPropertyAnimatable(propID)) {
+    return eCSSProperty_UNKNOWN;
+  }
+
+  // If we are animating the 'width' or 'height' of an outer SVG
+  // element we should animate it as a CSS property, but for other elements
+  // in SVG namespace (e.g. <rect>) we should animate it as a length attribute.
+  if ((mKey.mAttributeName == nsGkAtoms::width ||
+       mKey.mAttributeName == nsGkAtoms::height) &&
+      mKey.mElement->GetNameSpaceID() == kNameSpaceID_SVG) {
+    // Not an <svg> element.
+    if (!mKey.mElement->IsSVGElement(nsGkAtoms::svg)) {
+      return eCSSProperty_UNKNOWN;
+    }
+
+    // An inner <svg> element
+    if (static_cast<dom::SVGSVGElement const&>(*mKey.mElement).IsInner()) {
+      return eCSSProperty_UNKNOWN;
+    }
+
+    // Indeed an outer <svg> element, fall through.
+  }
+
+  return propID;
+}
+
+bool SMILCompositor::MightNeedBaseStyle() const {
+  if (GetCSSPropertyToAnimate() == eCSSProperty_UNKNOWN) {
+    return false;
+  }
+
+  // We should return true if at least one animation function might build on
+  // the base value.
+  for (const SMILAnimationFunction* func : mAnimationFunctions) {
+    if (!func->WillReplace()) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+uint32_t SMILCompositor::GetFirstFuncToAffectSandwich() {
+  // For performance reasons, we throttle most animations on elements in
+  // display:none subtrees. (We can't throttle animations that target the
+  // "display" property itself, though -- if we did, display:none elements
+  // could never be dynamically displayed via animations.)
+  // To determine whether we're in a display:none subtree, we will check the
+  // element's primary frame since element in display:none subtree doesn't have
+  // a primary frame. Before this process, we will construct frame when we
+  // append an element to subtree. So we will not need to worry about pending
+  // frame construction in this step.
+  bool canThrottle = mKey.mAttributeName != nsGkAtoms::display &&
+                     !mKey.mElement->GetPrimaryFrame();
+
+  uint32_t i;
+  for (i = mAnimationFunctions.Length(); i > 0; --i) {
+    SMILAnimationFunction* curAnimFunc = mAnimationFunctions[i - 1];
+    // In the following, the lack of short-circuit behavior of |= means that we
+    // will ALWAYS run UpdateCachedTarget (even if mForceCompositing is true)
+    // but only call HasChanged and WasSkippedInPrevSample if necessary.  This
+    // is important since we need UpdateCachedTarget to run in order to detect
+    // changes to the target in subsequent samples.
+    mForceCompositing |= curAnimFunc->UpdateCachedTarget(mKey) ||
+                         (curAnimFunc->HasChanged() && !canThrottle) ||
+                         curAnimFunc->WasSkippedInPrevSample();
+
+    if (curAnimFunc->WillReplace()) {
+      --i;
+      break;
+    }
+  }
+
+  // Mark remaining animation functions as having been skipped so if we later
+  // use them we'll know to force compositing.
+  // Note that we only really need to do this if something has changed
+  // (otherwise we would have set the flag on a previous sample) and if
+  // something has changed mForceCompositing will be true.
+  if (mForceCompositing) {
+    for (uint32_t j = i; j > 0; --j) {
+      mAnimationFunctions[j - 1]->SetWasSkipped();
+    }
+  }
+  return i;
+}
+
+void SMILCompositor::UpdateCachedBaseValue(const SMILValue& aBaseValue) {
+  if (mCachedBaseValue != aBaseValue) {
+    // Base value has changed since last sample.
+    mCachedBaseValue = aBaseValue;
+    mForceCompositing = true;
+  }
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILCompositor.h b/dom/smil/SMILCompositor.h
new file mode 100644
index 0000000000..5f987d5854
--- /dev/null
+++ b/dom/smil/SMILCompositor.h
@@ -0,0 +1,132 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILCOMPOSITOR_H_
+#define DOM_SMIL_SMILCOMPOSITOR_H_
+
+#include <utility>
+
+#include "PLDHashTable.h"
+#include "SMILTargetIdentifier.h"
+#include "mozilla/SMILAnimationFunction.h"
+#include "mozilla/SMILCompositorTable.h"
+#include "mozilla/UniquePtr.h"
+#include "nsCSSPropertyID.h"
+#include "nsString.h"
+#include "nsTHashtable.h"
+
+namespace mozilla {
+
+class ComputedStyle;
+
+//----------------------------------------------------------------------
+// SMILCompositor
+//
+// Performs the composition of the animation sandwich by combining the results
+// of a series animation functions according to the rules of SMIL composition
+// including prioritising animations.
+
+class SMILCompositor : public PLDHashEntryHdr {
+ public:
+  using KeyType = SMILTargetIdentifier;
+  using KeyTypeRef = const KeyType&;
+  using KeyTypePointer = const KeyType*;
+
+  explicit SMILCompositor(KeyTypePointer aKey)
+      : mKey(*aKey), mForceCompositing(false) {}
+  SMILCompositor(SMILCompositor&& toMove) noexcept
+      : PLDHashEntryHdr(std::move(toMove)),
+        mKey(std::move(toMove.mKey)),
+        mAnimationFunctions(std::move(toMove.mAnimationFunctions)),
+        mForceCompositing(false) {}
+
+  // PLDHashEntryHdr methods
+  KeyTypeRef GetKey() const { return mKey; }
+  bool KeyEquals(KeyTypePointer aKey) const;
+  static KeyTypePointer KeyToPointer(KeyTypeRef aKey) { return &aKey; }
+  static PLDHashNumber HashKey(KeyTypePointer aKey);
+  enum { ALLOW_MEMMOVE = false };
+
+  // Adds the given animation function to this Compositor's list of functions
+  void AddAnimationFunction(SMILAnimationFunction* aFunc);
+
+  // Composes the attribute's current value with the list of animation
+  // functions, and assigns the resulting value to this compositor's target
+  // attribute. If a change is made that might produce style updates,
+  // aMightHavePendingStyleUpdates is set to true. Otherwise it is not modified.
+  void ComposeAttribute(bool& aMightHavePendingStyleUpdates);
+
+  // Clears animation effects on my target attribute
+  void ClearAnimationEffects();
+
+  // Cycle-collection support
+  void Traverse(nsCycleCollectionTraversalCallback* aCallback);
+
+  // Toggles a bit that will force us to composite (bypassing early-return
+  // optimizations) when we hit ComposeAttribute.
+  void ToggleForceCompositing() { mForceCompositing = true; }
+
+  // Transfers |aOther|'s mCachedBaseValue to |this|
+  void StealCachedBaseValue(SMILCompositor* aOther) {
+    mCachedBaseValue = std::move(aOther->mCachedBaseValue);
+  }
+
+  bool HasSameNumberOfAnimationFunctionsAs(const SMILCompositor& aOther) const {
+    return mAnimationFunctions.Length() == aOther.mAnimationFunctions.Length();
+  }
+
+ private:
+  // Create a SMILAttr for my target, on the heap.
+  //
+  // @param aBaseComputedStyle  An optional ComputedStyle which, if set, will be
+  //                           used when fetching the base style.
+  UniquePtr<SMILAttr> CreateSMILAttr(const ComputedStyle* aBaseComputedStyle);
+
+  // Returns the CSS property this compositor should animate, or
+  // eCSSProperty_UNKNOWN if this compositor does not animate a CSS property.
+  nsCSSPropertyID GetCSSPropertyToAnimate() const;
+
+  // Returns true if we might need to refer to base styles (i.e. we are
+  // targeting a CSS property and have one or more animation functions that
+  // don't just replace the underlying value).
+  //
+  // This might return true in some cases where we don't actually need the base
+  // style since it doesn't build up the animation sandwich to check if the
+  // functions that appear to need the base style are actually replaced by
+  // a function further up the stack.
+  bool MightNeedBaseStyle() const;
+
+  // Finds the index of the first function that will affect our animation
+  // sandwich. Also toggles the 'mForceCompositing' flag if it finds that any
+  // (used) functions have changed.
+  uint32_t GetFirstFuncToAffectSandwich();
+
+  // If the passed-in base value differs from our cached base value, this
+  // method updates the cached value (and toggles the 'mForceCompositing' flag)
+  void UpdateCachedBaseValue(const SMILValue& aBaseValue);
+
+  // The hash key (tuple of element and attributeName)
+  KeyType mKey;
+
+  // Hash Value: List of animation functions that animate the specified attr
+  nsTArray<SMILAnimationFunction*> mAnimationFunctions;
+
+  // Member data for detecting when we need to force-recompose
+  // ---------------------------------------------------------
+  // Flag for tracking whether we need to compose. Initialized to false, but
+  // gets flipped to true if we detect that something has changed.
+  bool mForceCompositing;
+
+  // Cached base value, so we can detect & force-recompose when it changes
+  // from one sample to the next. (SMILAnimationController moves this
+  // forward from the previous sample's compositor by calling
+  // StealCachedBaseValue.)
+  SMILValue mCachedBaseValue;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILCOMPOSITOR_H_
diff --git a/dom/smil/SMILCompositorTable.h b/dom/smil/SMILCompositorTable.h
new file mode 100644
index 0000000000..649c108872
--- /dev/null
+++ b/dom/smil/SMILCompositorTable.h
@@ -0,0 +1,28 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILCOMPOSITORTABLE_H_
+#define DOM_SMIL_SMILCOMPOSITORTABLE_H_
+
+#include "nsTHashtable.h"
+
+//----------------------------------------------------------------------
+// SMILCompositorTable : A hashmap of SMILCompositors
+//
+// This is just a forward-declaration because it is included in
+// SMILAnimationController which is used in Document. We don't want to
+// expose all of SMILCompositor or otherwise any changes to it will mean the
+// whole world will need to be rebuilt.
+
+namespace mozilla {
+
+class SMILCompositor;
+
+using SMILCompositorTable = nsTHashtable<SMILCompositor>;
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILCOMPOSITORTABLE_H_
diff --git a/dom/smil/SMILEnumType.cpp b/dom/smil/SMILEnumType.cpp
new file mode 100644
index 0000000000..fbc5c6d2b8
--- /dev/null
+++ b/dom/smil/SMILEnumType.cpp
@@ -0,0 +1,69 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILEnumType.h"
+
+#include "mozilla/SMILValue.h"
+#include "nsDebug.h"
+#include <math.h>
+
+namespace mozilla {
+
+void SMILEnumType::Init(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.IsNull(), "Unexpected value type");
+  aValue.mU.mUint = 0;
+  aValue.mType = this;
+}
+
+void SMILEnumType::Destroy(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.mType == this, "Unexpected SMIL value");
+  aValue.mU.mUint = 0;
+  aValue.mType = SMILNullType::Singleton();
+}
+
+nsresult SMILEnumType::Assign(SMILValue& aDest, const SMILValue& aSrc) const {
+  MOZ_ASSERT(aDest.mType == aSrc.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aDest.mType == this, "Unexpected SMIL value");
+  aDest.mU.mUint = aSrc.mU.mUint;
+  return NS_OK;
+}
+
+bool SMILEnumType::IsEqual(const SMILValue& aLeft,
+                           const SMILValue& aRight) const {
+  MOZ_ASSERT(aLeft.mType == aRight.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aLeft.mType == this, "Unexpected type for SMIL value");
+
+  return aLeft.mU.mUint == aRight.mU.mUint;
+}
+
+nsresult SMILEnumType::Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+                           uint32_t aCount) const {
+  MOZ_ASSERT(aValueToAdd.mType == aDest.mType, "Trying to add invalid types");
+  MOZ_ASSERT(aValueToAdd.mType == this, "Unexpected source type");
+  return NS_ERROR_FAILURE;  // enum values can't be added to each other
+}
+
+nsresult SMILEnumType::ComputeDistance(const SMILValue& aFrom,
+                                       const SMILValue& aTo,
+                                       double& aDistance) const {
+  MOZ_ASSERT(aFrom.mType == aTo.mType, "Trying to compare different types");
+  MOZ_ASSERT(aFrom.mType == this, "Unexpected source type");
+  return NS_ERROR_FAILURE;  // there is no concept of distance between enum
+                            // values
+}
+
+nsresult SMILEnumType::Interpolate(const SMILValue& aStartVal,
+                                   const SMILValue& aEndVal,
+                                   double aUnitDistance,
+                                   SMILValue& aResult) const {
+  MOZ_ASSERT(aStartVal.mType == aEndVal.mType,
+             "Trying to interpolate different types");
+  MOZ_ASSERT(aStartVal.mType == this, "Unexpected types for interpolation");
+  MOZ_ASSERT(aResult.mType == this, "Unexpected result type");
+  return NS_ERROR_FAILURE;  // enum values do not interpolate
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILEnumType.h b/dom/smil/SMILEnumType.h
new file mode 100644
index 0000000000..a380ad21b7
--- /dev/null
+++ b/dom/smil/SMILEnumType.h
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILENUMTYPE_H_
+#define DOM_SMIL_SMILENUMTYPE_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILType.h"
+
+namespace mozilla {
+
+class SMILEnumType : public SMILType {
+ public:
+  // Singleton for SMILValue objects to hold onto.
+  static SMILEnumType* Singleton() {
+    static SMILEnumType sSingleton;
+    return &sSingleton;
+  }
+
+ protected:
+  // SMILType Methods
+  // -------------------
+  void Init(SMILValue& aValue) const override;
+  void Destroy(SMILValue& aValue) const override;
+  nsresult Assign(SMILValue& aDest, const SMILValue& aSrc) const override;
+  bool IsEqual(const SMILValue& aLeft, const SMILValue& aRight) const override;
+  nsresult Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+               uint32_t aCount) const override;
+  nsresult ComputeDistance(const SMILValue& aFrom, const SMILValue& aTo,
+                           double& aDistance) const override;
+  nsresult Interpolate(const SMILValue& aStartVal, const SMILValue& aEndVal,
+                       double aUnitDistance, SMILValue& aResult) const override;
+
+ private:
+  // Private constructor: prevent instances beyond my singleton.
+  constexpr SMILEnumType() = default;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILENUMTYPE_H_
diff --git a/dom/smil/SMILFloatType.cpp b/dom/smil/SMILFloatType.cpp
new file mode 100644
index 0000000000..ac50cfe8d2
--- /dev/null
+++ b/dom/smil/SMILFloatType.cpp
@@ -0,0 +1,81 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILFloatType.h"
+
+#include "mozilla/SMILValue.h"
+#include "nsDebug.h"
+#include <math.h>
+
+namespace mozilla {
+
+void SMILFloatType::Init(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.IsNull(), "Unexpected value type");
+  aValue.mU.mDouble = 0.0;
+  aValue.mType = this;
+}
+
+void SMILFloatType::Destroy(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.mType == this, "Unexpected SMIL value");
+  aValue.mU.mDouble = 0.0;
+  aValue.mType = SMILNullType::Singleton();
+}
+
+nsresult SMILFloatType::Assign(SMILValue& aDest, const SMILValue& aSrc) const {
+  MOZ_ASSERT(aDest.mType == aSrc.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aDest.mType == this, "Unexpected SMIL value");
+  aDest.mU.mDouble = aSrc.mU.mDouble;
+  return NS_OK;
+}
+
+bool SMILFloatType::IsEqual(const SMILValue& aLeft,
+                            const SMILValue& aRight) const {
+  MOZ_ASSERT(aLeft.mType == aRight.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aLeft.mType == this, "Unexpected type for SMIL value");
+
+  return aLeft.mU.mDouble == aRight.mU.mDouble;
+}
+
+nsresult SMILFloatType::Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+                            uint32_t aCount) const {
+  MOZ_ASSERT(aValueToAdd.mType == aDest.mType, "Trying to add invalid types");
+  MOZ_ASSERT(aValueToAdd.mType == this, "Unexpected source type");
+  aDest.mU.mDouble += aValueToAdd.mU.mDouble * aCount;
+  return NS_OK;
+}
+
+nsresult SMILFloatType::ComputeDistance(const SMILValue& aFrom,
+                                        const SMILValue& aTo,
+                                        double& aDistance) const {
+  MOZ_ASSERT(aFrom.mType == aTo.mType, "Trying to compare different types");
+  MOZ_ASSERT(aFrom.mType == this, "Unexpected source type");
+
+  const double& from = aFrom.mU.mDouble;
+  const double& to = aTo.mU.mDouble;
+
+  aDistance = fabs(to - from);
+
+  return NS_OK;
+}
+
+nsresult SMILFloatType::Interpolate(const SMILValue& aStartVal,
+                                    const SMILValue& aEndVal,
+                                    double aUnitDistance,
+                                    SMILValue& aResult) const {
+  MOZ_ASSERT(aStartVal.mType == aEndVal.mType,
+             "Trying to interpolate different types");
+  MOZ_ASSERT(aStartVal.mType == this, "Unexpected types for interpolation");
+  MOZ_ASSERT(aResult.mType == this, "Unexpected result type");
+
+  const double& startVal = aStartVal.mU.mDouble;
+  const double& endVal = aEndVal.mU.mDouble;
+
+  aResult.mU.mDouble = (startVal + (endVal - startVal) * aUnitDistance);
+
+  return NS_OK;
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILFloatType.h b/dom/smil/SMILFloatType.h
new file mode 100644
index 0000000000..18e3d0fdfa
--- /dev/null
+++ b/dom/smil/SMILFloatType.h
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILFLOATTYPE_H_
+#define DOM_SMIL_SMILFLOATTYPE_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILType.h"
+
+namespace mozilla {
+
+class SMILFloatType : public SMILType {
+ public:
+  // Singleton for SMILValue objects to hold onto.
+  static SMILFloatType* Singleton() {
+    static SMILFloatType sSingleton;
+    return &sSingleton;
+  }
+
+ protected:
+  // SMILType Methods
+  // -------------------
+  void Init(SMILValue& aValue) const override;
+  void Destroy(SMILValue& aValue) const override;
+  nsresult Assign(SMILValue& aDest, const SMILValue& aSrc) const override;
+  bool IsEqual(const SMILValue& aLeft, const SMILValue& aRight) const override;
+  nsresult Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+               uint32_t aCount) const override;
+  nsresult ComputeDistance(const SMILValue& aFrom, const SMILValue& aTo,
+                           double& aDistance) const override;
+  nsresult Interpolate(const SMILValue& aStartVal, const SMILValue& aEndVal,
+                       double aUnitDistance, SMILValue& aResult) const override;
+
+ private:
+  // Private constructor: prevent instances beyond my singleton.
+  constexpr SMILFloatType() = default;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILFLOATTYPE_H_
diff --git a/dom/smil/SMILInstanceTime.cpp b/dom/smil/SMILInstanceTime.cpp
new file mode 100644
index 0000000000..7f38b8c1d7
--- /dev/null
+++ b/dom/smil/SMILInstanceTime.cpp
@@ -0,0 +1,188 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILInstanceTime.h"
+
+#include "mozilla/AutoRestore.h"
+#include "mozilla/SMILInterval.h"
+#include "mozilla/SMILTimeValueSpec.h"
+
+namespace mozilla {
+
+//----------------------------------------------------------------------
+// Implementation
+
+SMILInstanceTime::SMILInstanceTime(const SMILTimeValue& aTime,
+                                   SMILInstanceTimeSource aSource,
+                                   SMILTimeValueSpec* aCreator,
+                                   SMILInterval* aBaseInterval)
+    : mTime(aTime),
+      mFlags(0),
+      mVisited(false),
+      mFixedEndpointRefCnt(0),
+      mSerial(0),
+      mCreator(aCreator),
+      mBaseInterval(nullptr)  // This will get set to aBaseInterval in a call to
+                              // SetBaseInterval() at end of constructor
+{
+  switch (aSource) {
+    case SOURCE_NONE:
+      // No special flags
+      break;
+
+    case SOURCE_DOM:
+      mFlags = kDynamic | kFromDOM;
+      break;
+
+    case SOURCE_SYNCBASE:
+      mFlags = kMayUpdate;
+      break;
+
+    case SOURCE_EVENT:
+      mFlags = kDynamic;
+      break;
+  }
+
+  SetBaseInterval(aBaseInterval);
+}
+
+SMILInstanceTime::~SMILInstanceTime() {
+  MOZ_ASSERT(!mBaseInterval,
+             "Destroying instance time without first calling Unlink()");
+  MOZ_ASSERT(mFixedEndpointRefCnt == 0,
+             "Destroying instance time that is still used as the fixed "
+             "endpoint of an interval");
+}
+
+void SMILInstanceTime::Unlink() {
+  RefPtr<SMILInstanceTime> deathGrip(this);
+  if (mBaseInterval) {
+    mBaseInterval->RemoveDependentTime(*this);
+    mBaseInterval = nullptr;
+  }
+  mCreator = nullptr;
+}
+
+void SMILInstanceTime::HandleChangedInterval(
+    const SMILTimeContainer* aSrcContainer, bool aBeginObjectChanged,
+    bool aEndObjectChanged) {
+  // It's possible a sequence of notifications might cause our base interval to
+  // be updated and then deleted. Furthermore, the delete might happen whilst
+  // we're still in the queue to be notified of the change. In any case, if we
+  // don't have a base interval, just ignore the change.
+  if (!mBaseInterval) return;
+
+  MOZ_ASSERT(mCreator, "Base interval is set but creator is not.");
+
+  if (mVisited) {
+    // Break the cycle here
+    Unlink();
+    return;
+  }
+
+  bool objectChanged =
+      mCreator->DependsOnBegin() ? aBeginObjectChanged : aEndObjectChanged;
+
+  RefPtr<SMILInstanceTime> deathGrip(this);
+  mozilla::AutoRestore<bool> setVisited(mVisited);
+  mVisited = true;
+
+  mCreator->HandleChangedInstanceTime(*GetBaseTime(), aSrcContainer, *this,
+                                      objectChanged);
+}
+
+void SMILInstanceTime::HandleDeletedInterval() {
+  MOZ_ASSERT(mBaseInterval,
+             "Got call to HandleDeletedInterval on an independent instance "
+             "time");
+  MOZ_ASSERT(mCreator, "Base interval is set but creator is not");
+
+  mBaseInterval = nullptr;
+  mFlags &= ~kMayUpdate;  // Can't update without a base interval
+
+  RefPtr<SMILInstanceTime> deathGrip(this);
+  mCreator->HandleDeletedInstanceTime(*this);
+  mCreator = nullptr;
+}
+
+void SMILInstanceTime::HandleFilteredInterval() {
+  MOZ_ASSERT(mBaseInterval,
+             "Got call to HandleFilteredInterval on an independent instance "
+             "time");
+
+  mBaseInterval = nullptr;
+  mFlags &= ~kMayUpdate;  // Can't update without a base interval
+  mCreator = nullptr;
+}
+
+bool SMILInstanceTime::ShouldPreserve() const {
+  return mFixedEndpointRefCnt > 0 || (mFlags & kWasDynamicEndpoint);
+}
+
+void SMILInstanceTime::UnmarkShouldPreserve() {
+  mFlags &= ~kWasDynamicEndpoint;
+}
+
+void SMILInstanceTime::AddRefFixedEndpoint() {
+  MOZ_ASSERT(mFixedEndpointRefCnt < UINT16_MAX,
+             "Fixed endpoint reference count upper limit reached");
+  ++mFixedEndpointRefCnt;
+  mFlags &= ~kMayUpdate;  // Once fixed, always fixed
+}
+
+void SMILInstanceTime::ReleaseFixedEndpoint() {
+  MOZ_ASSERT(mFixedEndpointRefCnt > 0, "Duplicate release");
+  --mFixedEndpointRefCnt;
+  if (mFixedEndpointRefCnt == 0 && IsDynamic()) {
+    mFlags |= kWasDynamicEndpoint;
+  }
+}
+
+bool SMILInstanceTime::IsDependentOn(const SMILInstanceTime& aOther) const {
+  if (mVisited) return false;
+
+  const SMILInstanceTime* myBaseTime = GetBaseTime();
+  if (!myBaseTime) return false;
+
+  if (myBaseTime == &aOther) return true;
+
+  mozilla::AutoRestore<bool> setVisited(mVisited);
+  mVisited = true;
+  return myBaseTime->IsDependentOn(aOther);
+}
+
+const SMILInstanceTime* SMILInstanceTime::GetBaseTime() const {
+  if (!mBaseInterval) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(mCreator, "Base interval is set but there is no creator.");
+  if (!mCreator) {
+    return nullptr;
+  }
+
+  return mCreator->DependsOnBegin() ? mBaseInterval->Begin()
+                                    : mBaseInterval->End();
+}
+
+void SMILInstanceTime::SetBaseInterval(SMILInterval* aBaseInterval) {
+  MOZ_ASSERT(!mBaseInterval,
+             "Attempting to reassociate an instance time with a different "
+             "interval.");
+
+  if (aBaseInterval) {
+    MOZ_ASSERT(mCreator,
+               "Attempting to create a dependent instance time without "
+               "reference to the creating SMILTimeValueSpec object.");
+    if (!mCreator) return;
+
+    aBaseInterval->AddDependentTime(*this);
+  }
+
+  mBaseInterval = aBaseInterval;
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILInstanceTime.h b/dom/smil/SMILInstanceTime.h
new file mode 100644
index 0000000000..1224cfc8fe
--- /dev/null
+++ b/dom/smil/SMILInstanceTime.h
@@ -0,0 +1,166 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILINSTANCETIME_H_
+#define DOM_SMIL_SMILINSTANCETIME_H_
+
+#include "nsISupportsImpl.h"
+#include "mozilla/SMILTimeValue.h"
+
+namespace mozilla {
+class SMILInterval;
+class SMILTimeContainer;
+class SMILTimeValueSpec;
+
+//----------------------------------------------------------------------
+// SMILInstanceTime
+//
+// An instant in document simple time that may be used in creating a new
+// interval.
+//
+// For an overview of how this class is related to other SMIL time classes see
+// the documentation in SMILTimeValue.h
+//
+// These objects are owned by an SMILTimedElement but MAY also be referenced
+// by:
+//
+// a) SMILIntervals that belong to the same SMILTimedElement and which refer
+//    to the SMILInstanceTimes which form the interval endpoints; and/or
+// b) SMILIntervals that belong to other SMILTimedElements but which need to
+//    update dependent instance times when they change or are deleted.
+//    E.g. for begin='a.begin', 'a' needs to inform dependent
+//    SMILInstanceTimes if its begin time changes. This notification is
+//    performed by the SMILInterval.
+
+class SMILInstanceTime final {
+ public:
+  // Instance time source. Times generated by events, syncbase relationships,
+  // and DOM calls behave differently in some circumstances such as when a timed
+  // element is reset.
+  enum SMILInstanceTimeSource {
+    // No particularly significant source, e.g. offset time, 'indefinite'
+    SOURCE_NONE,
+    // Generated by a DOM call such as beginElement
+    SOURCE_DOM,
+    // Generated by a syncbase relationship
+    SOURCE_SYNCBASE,
+    // Generated by an event
+    SOURCE_EVENT
+  };
+
+  explicit SMILInstanceTime(const SMILTimeValue& aTime,
+                            SMILInstanceTimeSource aSource = SOURCE_NONE,
+                            SMILTimeValueSpec* aCreator = nullptr,
+                            SMILInterval* aBaseInterval = nullptr);
+
+  void Unlink();
+  void HandleChangedInterval(const SMILTimeContainer* aSrcContainer,
+                             bool aBeginObjectChanged, bool aEndObjectChanged);
+  void HandleDeletedInterval();
+  void HandleFilteredInterval();
+
+  const SMILTimeValue& Time() const { return mTime; }
+  const SMILTimeValueSpec* GetCreator() const { return mCreator; }
+
+  bool IsDynamic() const { return !!(mFlags & kDynamic); }
+  bool IsFixedTime() const { return !(mFlags & kMayUpdate); }
+  bool FromDOM() const { return !!(mFlags & kFromDOM); }
+
+  bool ShouldPreserve() const;
+  void UnmarkShouldPreserve();
+
+  void AddRefFixedEndpoint();
+  void ReleaseFixedEndpoint();
+
+  void DependentUpdate(const SMILTimeValue& aNewTime) {
+    MOZ_ASSERT(!IsFixedTime(),
+               "Updating an instance time that is not expected to be updated");
+    mTime = aNewTime;
+  }
+
+  bool IsDependent() const { return !!mBaseInterval; }
+  bool IsDependentOn(const SMILInstanceTime& aOther) const;
+  const SMILInterval* GetBaseInterval() const { return mBaseInterval; }
+  const SMILInstanceTime* GetBaseTime() const;
+
+  bool SameTimeAndBase(const SMILInstanceTime& aOther) const {
+    return mTime == aOther.mTime && GetBaseTime() == aOther.GetBaseTime();
+  }
+
+  // Get and set a serial number which may be used by a containing class to
+  // control the sort order of otherwise similar instance times.
+  uint32_t Serial() const { return mSerial; }
+  void SetSerial(uint32_t aIndex) { mSerial = aIndex; }
+
+  NS_INLINE_DECL_REFCOUNTING(SMILInstanceTime)
+
+ private:
+  // Private destructor, to discourage deletion outside of Release():
+  ~SMILInstanceTime();
+
+  void SetBaseInterval(SMILInterval* aBaseInterval);
+
+  SMILTimeValue mTime;
+
+  // Internal flags used to represent the behaviour of different instance times
+  enum {
+    // Indicates that this instance time was generated by an event or a DOM
+    // call. Such instance times require special handling when (i) the owning
+    // element is reset, (ii) when they are to be added as a new end instance
+    // times (as per SMIL's event sensitivity contraints), and (iii) when
+    // a backwards seek is performed and the timing model is reconstructed.
+    kDynamic = 1,
+
+    // Indicates that this instance time is referred to by an
+    // SMILTimeValueSpec and as such may be updated. Such instance time should
+    // not be filtered out by the SMILTimedElement even if they appear to be
+    // in the past as they may be updated to a future time.
+    kMayUpdate = 2,
+
+    // Indicates that this instance time was generated from the DOM as opposed
+    // to an SMILTimeValueSpec. When a 'begin' or 'end' attribute is set or
+    // reset we should clear all the instance times that have been generated by
+    // that attribute (and hence an SMILTimeValueSpec), but not those from the
+    // DOM.
+    kFromDOM = 4,
+
+    // Indicates that this instance time was used as the endpoint of an interval
+    // that has been filtered or removed. However, since it is a dynamic time it
+    // should be preserved and not filtered.
+    kWasDynamicEndpoint = 8
+  };
+  uint8_t mFlags;         // Combination of kDynamic, kMayUpdate, etc.
+  mutable bool mVisited;  // Cycle tracking
+
+  // Additional reference count to determine if this instance time is currently
+  // used as a fixed endpoint in any intervals. Instance times that are used in
+  // this way should not be removed when the owning SMILTimedElement removes
+  // instance times in response to a restart or in an attempt to free up memory
+  // by filtering out old instance times.
+  //
+  // Instance times are only shared in a few cases, namely:
+  // a) early ends,
+  // b) zero-duration intervals,
+  // c) momentarily whilst establishing new intervals and updating the current
+  //    interval, and
+  // d) trimmed intervals
+  // Hence the limited range of a uint16_t should be more than adequate.
+  uint16_t mFixedEndpointRefCnt;
+
+  uint32_t mSerial;  // A serial number used by the containing class to
+                     // specify the sort order for instance times with the
+                     // same mTime.
+
+  SMILTimeValueSpec* mCreator;  // The SMILTimeValueSpec object that created
+                                // us. (currently only needed for syncbase
+                                // instance times.)
+  SMILInterval* mBaseInterval;  // Interval from which this time is derived
+                                // (only used for syncbase instance times)
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILINSTANCETIME_H_
diff --git a/dom/smil/SMILIntegerType.cpp b/dom/smil/SMILIntegerType.cpp
new file mode 100644
index 0000000000..c1ac207836
--- /dev/null
+++ b/dom/smil/SMILIntegerType.cpp
@@ -0,0 +1,86 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILIntegerType.h"
+
+#include "mozilla/SMILValue.h"
+#include "nsDebug.h"
+#include <math.h>
+
+namespace mozilla {
+
+void SMILIntegerType::Init(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.IsNull(), "Unexpected value type");
+  aValue.mU.mInt = 0;
+  aValue.mType = this;
+}
+
+void SMILIntegerType::Destroy(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.mType == this, "Unexpected SMIL value");
+  aValue.mU.mInt = 0;
+  aValue.mType = SMILNullType::Singleton();
+}
+
+nsresult SMILIntegerType::Assign(SMILValue& aDest,
+                                 const SMILValue& aSrc) const {
+  MOZ_ASSERT(aDest.mType == aSrc.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aDest.mType == this, "Unexpected SMIL value");
+  aDest.mU.mInt = aSrc.mU.mInt;
+  return NS_OK;
+}
+
+bool SMILIntegerType::IsEqual(const SMILValue& aLeft,
+                              const SMILValue& aRight) const {
+  MOZ_ASSERT(aLeft.mType == aRight.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aLeft.mType == this, "Unexpected type for SMIL value");
+
+  return aLeft.mU.mInt == aRight.mU.mInt;
+}
+
+nsresult SMILIntegerType::Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+                              uint32_t aCount) const {
+  MOZ_ASSERT(aValueToAdd.mType == aDest.mType, "Trying to add invalid types");
+  MOZ_ASSERT(aValueToAdd.mType == this, "Unexpected source type");
+  aDest.mU.mInt += aValueToAdd.mU.mInt * aCount;
+  return NS_OK;
+}
+
+nsresult SMILIntegerType::ComputeDistance(const SMILValue& aFrom,
+                                          const SMILValue& aTo,
+                                          double& aDistance) const {
+  MOZ_ASSERT(aFrom.mType == aTo.mType, "Trying to compare different types");
+  MOZ_ASSERT(aFrom.mType == this, "Unexpected source type");
+  aDistance = fabs(double(aTo.mU.mInt - aFrom.mU.mInt));
+  return NS_OK;
+}
+
+nsresult SMILIntegerType::Interpolate(const SMILValue& aStartVal,
+                                      const SMILValue& aEndVal,
+                                      double aUnitDistance,
+                                      SMILValue& aResult) const {
+  MOZ_ASSERT(aStartVal.mType == aEndVal.mType,
+             "Trying to interpolate different types");
+  MOZ_ASSERT(aStartVal.mType == this, "Unexpected types for interpolation");
+  MOZ_ASSERT(aResult.mType == this, "Unexpected result type");
+
+  const double startVal = double(aStartVal.mU.mInt);
+  const double endVal = double(aEndVal.mU.mInt);
+  const double currentVal = startVal + (endVal - startVal) * aUnitDistance;
+
+  // When currentVal is exactly midway between its two nearest integers, we
+  // jump to the "next" integer to provide simple, easy to remember and
+  // consistent behaviour (from the SMIL author's point of view).
+
+  if (startVal < endVal) {
+    aResult.mU.mInt = int64_t(floor(currentVal + 0.5));  // round mid up
+  } else {
+    aResult.mU.mInt = int64_t(ceil(currentVal - 0.5));  // round mid down
+  }
+
+  return NS_OK;
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILIntegerType.h b/dom/smil/SMILIntegerType.h
new file mode 100644
index 0000000000..6bdff63d80
--- /dev/null
+++ b/dom/smil/SMILIntegerType.h
@@ -0,0 +1,39 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILINTEGERTYPE_H_
+#define DOM_SMIL_SMILINTEGERTYPE_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILType.h"
+
+namespace mozilla {
+
+class SMILIntegerType : public SMILType {
+ public:
+  void Init(SMILValue& aValue) const override;
+  void Destroy(SMILValue& aValue) const override;
+  nsresult Assign(SMILValue& aDest, const SMILValue& aSrc) const override;
+  bool IsEqual(const SMILValue& aLeft, const SMILValue& aRight) const override;
+  nsresult Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+               uint32_t aCount) const override;
+  nsresult ComputeDistance(const SMILValue& aFrom, const SMILValue& aTo,
+                           double& aDistance) const override;
+  nsresult Interpolate(const SMILValue& aStartVal, const SMILValue& aEndVal,
+                       double aUnitDistance, SMILValue& aResult) const override;
+
+  static SMILIntegerType* Singleton() {
+    static SMILIntegerType sSingleton;
+    return &sSingleton;
+  }
+
+ private:
+  constexpr SMILIntegerType() = default;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILINTEGERTYPE_H_
diff --git a/dom/smil/SMILInterval.cpp b/dom/smil/SMILInterval.cpp
new file mode 100644
index 0000000000..e0ee99ac00
--- /dev/null
+++ b/dom/smil/SMILInterval.cpp
@@ -0,0 +1,137 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILInterval.h"
+
+#include "mozilla/DebugOnly.h"
+
+namespace mozilla {
+
+SMILInterval::SMILInterval() : mBeginFixed(false), mEndFixed(false) {}
+
+SMILInterval::SMILInterval(const SMILInterval& aOther)
+    : mBegin(aOther.mBegin),
+      mEnd(aOther.mEnd),
+      mBeginFixed(false),
+      mEndFixed(false) {
+  MOZ_ASSERT(aOther.mDependentTimes.IsEmpty(),
+             "Attempt to copy-construct an interval with dependent times; this "
+             "will lead to instance times being shared between intervals.");
+
+  // For the time being we don't allow intervals with fixed endpoints to be
+  // copied since we only ever copy-construct to establish a new current
+  // interval. If we ever need to copy historical intervals we may need to move
+  // the ReleaseFixedEndpoint calls from Unlink to the dtor.
+  MOZ_ASSERT(!aOther.mBeginFixed && !aOther.mEndFixed,
+             "Attempt to copy-construct an interval with fixed endpoints");
+}
+
+SMILInterval::~SMILInterval() {
+  MOZ_ASSERT(mDependentTimes.IsEmpty(),
+             "Destroying interval without disassociating dependent instance "
+             "times. Unlink was not called");
+}
+
+void SMILInterval::Unlink(bool aFiltered) {
+  for (int32_t i = mDependentTimes.Length() - 1; i >= 0; --i) {
+    if (aFiltered) {
+      mDependentTimes[i]->HandleFilteredInterval();
+    } else {
+      mDependentTimes[i]->HandleDeletedInterval();
+    }
+  }
+  mDependentTimes.Clear();
+  if (mBegin && mBeginFixed) {
+    mBegin->ReleaseFixedEndpoint();
+  }
+  mBegin = nullptr;
+  if (mEnd && mEndFixed) {
+    mEnd->ReleaseFixedEndpoint();
+  }
+  mEnd = nullptr;
+}
+
+SMILInstanceTime* SMILInterval::Begin() {
+  MOZ_ASSERT(mBegin && mEnd, "Requesting Begin() on un-initialized interval.");
+  return mBegin;
+}
+
+SMILInstanceTime* SMILInterval::End() {
+  MOZ_ASSERT(mBegin && mEnd, "Requesting End() on un-initialized interval.");
+  return mEnd;
+}
+
+void SMILInterval::SetBegin(SMILInstanceTime& aBegin) {
+  MOZ_ASSERT(aBegin.Time().IsDefinite(),
+             "Attempt to set unresolved or indefinite begin time on interval");
+  MOZ_ASSERT(!mBeginFixed,
+             "Attempt to set begin time but the begin point is fixed");
+  // Check that we're not making an instance time dependent on itself. Such an
+  // arrangement does not make intuitive sense and should be detected when
+  // creating or updating intervals.
+  MOZ_ASSERT(!mBegin || aBegin.GetBaseTime() != mBegin,
+             "Attempt to make self-dependent instance time");
+
+  mBegin = &aBegin;
+}
+
+void SMILInterval::SetEnd(SMILInstanceTime& aEnd) {
+  MOZ_ASSERT(!mEndFixed, "Attempt to set end time but the end point is fixed");
+  // As with SetBegin, check we're not making an instance time dependent on
+  // itself.
+  MOZ_ASSERT(!mEnd || aEnd.GetBaseTime() != mEnd,
+             "Attempting to make self-dependent instance time");
+
+  mEnd = &aEnd;
+}
+
+void SMILInterval::FixBegin() {
+  MOZ_ASSERT(mBegin && mEnd, "Fixing begin point on un-initialized interval");
+  MOZ_ASSERT(!mBeginFixed, "Duplicate calls to FixBegin()");
+  mBeginFixed = true;
+  mBegin->AddRefFixedEndpoint();
+}
+
+void SMILInterval::FixEnd() {
+  MOZ_ASSERT(mBegin && mEnd, "Fixing end point on un-initialized interval");
+  MOZ_ASSERT(mBeginFixed,
+             "Fixing the end of an interval without a fixed begin");
+  MOZ_ASSERT(!mEndFixed, "Duplicate calls to FixEnd()");
+  mEndFixed = true;
+  mEnd->AddRefFixedEndpoint();
+}
+
+void SMILInterval::AddDependentTime(SMILInstanceTime& aTime) {
+  RefPtr<SMILInstanceTime>* inserted =
+      mDependentTimes.InsertElementSorted(&aTime);
+  if (!inserted) {
+    NS_WARNING("Insufficient memory to insert instance time.");
+  }
+}
+
+void SMILInterval::RemoveDependentTime(const SMILInstanceTime& aTime) {
+  DebugOnly<bool> found = mDependentTimes.RemoveElementSorted(&aTime);
+  MOZ_ASSERT(found, "Couldn't find instance time to delete.");
+}
+
+void SMILInterval::GetDependentTimes(InstanceTimeList& aTimes) {
+  aTimes = mDependentTimes.Clone();
+}
+
+bool SMILInterval::IsDependencyChainLink() const {
+  if (!mBegin || !mEnd)
+    return false;  // Not yet initialised so it can't be part of a chain
+
+  if (mDependentTimes.IsEmpty()) return false;  // No dependents, chain end
+
+  // So we have dependents, but we're still only a link in the chain (as opposed
+  // to the end of the chain) if one of our endpoints is dependent on an
+  // interval other than ourselves.
+  return (mBegin->IsDependent() && mBegin->GetBaseInterval() != this) ||
+         (mEnd->IsDependent() && mEnd->GetBaseInterval() != this);
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILInterval.h b/dom/smil/SMILInterval.h
new file mode 100644
index 0000000000..a569fce147
--- /dev/null
+++ b/dom/smil/SMILInterval.h
@@ -0,0 +1,86 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILINTERVAL_H_
+#define DOM_SMIL_SMILINTERVAL_H_
+
+#include "mozilla/SMILInstanceTime.h"
+#include "nsTArray.h"
+
+namespace mozilla {
+
+//----------------------------------------------------------------------
+// SMILInterval class
+//
+// A structure consisting of a begin and end time. The begin time must be
+// resolved (i.e. not indefinite or unresolved).
+//
+// For an overview of how this class is related to other SMIL time classes see
+// the documentation in SMILTimeValue.h
+
+class SMILInterval {
+ public:
+  SMILInterval();
+  SMILInterval(const SMILInterval& aOther);
+  ~SMILInterval();
+  void Unlink(bool aFiltered = false);
+
+  const SMILInstanceTime* Begin() const {
+    MOZ_ASSERT(mBegin && mEnd,
+               "Requesting Begin() on un-initialized instance time");
+    return mBegin;
+  }
+  SMILInstanceTime* Begin();
+
+  const SMILInstanceTime* End() const {
+    MOZ_ASSERT(mBegin && mEnd,
+               "Requesting End() on un-initialized instance time");
+    return mEnd;
+  }
+  SMILInstanceTime* End();
+
+  void SetBegin(SMILInstanceTime& aBegin);
+  void SetEnd(SMILInstanceTime& aEnd);
+  void Set(SMILInstanceTime& aBegin, SMILInstanceTime& aEnd) {
+    SetBegin(aBegin);
+    SetEnd(aEnd);
+  }
+
+  void FixBegin();
+  void FixEnd();
+
+  using InstanceTimeList = nsTArray<RefPtr<SMILInstanceTime>>;
+
+  void AddDependentTime(SMILInstanceTime& aTime);
+  void RemoveDependentTime(const SMILInstanceTime& aTime);
+  void GetDependentTimes(InstanceTimeList& aTimes);
+
+  // Cue for assessing if this interval can be filtered
+  bool IsDependencyChainLink() const;
+
+ private:
+  RefPtr<SMILInstanceTime> mBegin;
+  RefPtr<SMILInstanceTime> mEnd;
+
+  // SMILInstanceTimes to notify when this interval is changed or deleted.
+  InstanceTimeList mDependentTimes;
+
+  // Indicates if the end points of the interval are fixed or not.
+  //
+  // Note that this is not the same as having an end point whose TIME is fixed
+  // (i.e. SMILInstanceTime::IsFixed() returns true). This is because it is
+  // possible to have an end point with a fixed TIME and yet still update the
+  // end point to refer to a different SMILInstanceTime object.
+  //
+  // However, if mBegin/EndFixed is true, then BOTH the SMILInstanceTime
+  // OBJECT returned for that end point and its TIME value will not change.
+  bool mBeginFixed;
+  bool mEndFixed;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILINTERVAL_H_
diff --git a/dom/smil/SMILKeySpline.cpp b/dom/smil/SMILKeySpline.cpp
new file mode 100644
index 0000000000..dd508e1bcb
--- /dev/null
+++ b/dom/smil/SMILKeySpline.cpp
@@ -0,0 +1,127 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILKeySpline.h"
+#include <stdint.h>
+#include <math.h>
+
+namespace mozilla {
+
+#define NEWTON_ITERATIONS 4
+#define NEWTON_MIN_SLOPE 0.02
+#define SUBDIVISION_PRECISION 0.0000001
+#define SUBDIVISION_MAX_ITERATIONS 10
+
+const double SMILKeySpline::kSampleStepSize =
+    1.0 / double(kSplineTableSize - 1);
+
+void SMILKeySpline::Init(double aX1, double aY1, double aX2, double aY2) {
+  mX1 = aX1;
+  mY1 = aY1;
+  mX2 = aX2;
+  mY2 = aY2;
+
+  if (mX1 != mY1 || mX2 != mY2) CalcSampleValues();
+}
+
+double SMILKeySpline::GetSplineValue(double aX) const {
+  if (mX1 == mY1 && mX2 == mY2) return aX;
+
+  return CalcBezier(GetTForX(aX), mY1, mY2);
+}
+
+void SMILKeySpline::GetSplineDerivativeValues(double aX, double& aDX,
+                                              double& aDY) const {
+  double t = GetTForX(aX);
+  aDX = GetSlope(t, mX1, mX2);
+  aDY = GetSlope(t, mY1, mY2);
+}
+
+void SMILKeySpline::CalcSampleValues() {
+  for (uint32_t i = 0; i < kSplineTableSize; ++i) {
+    mSampleValues[i] = CalcBezier(double(i) * kSampleStepSize, mX1, mX2);
+  }
+}
+
+/*static*/
+double SMILKeySpline::CalcBezier(double aT, double aA1, double aA2) {
+  // use Horner's scheme to evaluate the Bezier polynomial
+  return ((A(aA1, aA2) * aT + B(aA1, aA2)) * aT + C(aA1)) * aT;
+}
+
+/*static*/
+double SMILKeySpline::GetSlope(double aT, double aA1, double aA2) {
+  return 3.0 * A(aA1, aA2) * aT * aT + 2.0 * B(aA1, aA2) * aT + C(aA1);
+}
+
+double SMILKeySpline::GetTForX(double aX) const {
+  // Early return when aX == 1.0 to avoid floating-point inaccuracies.
+  if (aX == 1.0) {
+    return 1.0;
+  }
+  // Find interval where t lies
+  double intervalStart = 0.0;
+  const double* currentSample = &mSampleValues[1];
+  const double* const lastSample = &mSampleValues[kSplineTableSize - 1];
+  for (; currentSample != lastSample && *currentSample <= aX; ++currentSample) {
+    intervalStart += kSampleStepSize;
+  }
+  --currentSample;  // t now lies between *currentSample and *currentSample+1
+
+  // Interpolate to provide an initial guess for t
+  double dist = (aX - *currentSample) / (*(currentSample + 1) - *currentSample);
+  double guessForT = intervalStart + dist * kSampleStepSize;
+
+  // Check the slope to see what strategy to use. If the slope is too small
+  // Newton-Raphson iteration won't converge on a root so we use bisection
+  // instead.
+  double initialSlope = GetSlope(guessForT, mX1, mX2);
+  if (initialSlope >= NEWTON_MIN_SLOPE) {
+    return NewtonRaphsonIterate(aX, guessForT);
+  }
+  if (initialSlope == 0.0) {
+    return guessForT;
+  }
+  return BinarySubdivide(aX, intervalStart, intervalStart + kSampleStepSize);
+}
+
+double SMILKeySpline::NewtonRaphsonIterate(double aX, double aGuessT) const {
+  // Refine guess with Newton-Raphson iteration
+  for (uint32_t i = 0; i < NEWTON_ITERATIONS; ++i) {
+    // We're trying to find where f(t) = aX,
+    // so we're actually looking for a root for: CalcBezier(t) - aX
+    double currentX = CalcBezier(aGuessT, mX1, mX2) - aX;
+    double currentSlope = GetSlope(aGuessT, mX1, mX2);
+
+    if (currentSlope == 0.0) return aGuessT;
+
+    aGuessT -= currentX / currentSlope;
+  }
+
+  return aGuessT;
+}
+
+double SMILKeySpline::BinarySubdivide(double aX, double aA, double aB) const {
+  double currentX;
+  double currentT;
+  uint32_t i = 0;
+
+  do {
+    currentT = aA + (aB - aA) / 2.0;
+    currentX = CalcBezier(currentT, mX1, mX2) - aX;
+
+    if (currentX > 0.0) {
+      aB = currentT;
+    } else {
+      aA = currentT;
+    }
+  } while (fabs(currentX) > SUBDIVISION_PRECISION &&
+           ++i < SUBDIVISION_MAX_ITERATIONS);
+
+  return currentT;
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILKeySpline.h b/dom/smil/SMILKeySpline.h
new file mode 100644
index 0000000000..d5f180e94a
--- /dev/null
+++ b/dom/smil/SMILKeySpline.h
@@ -0,0 +1,107 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILKEYSPLINE_H_
+#define DOM_SMIL_SMILKEYSPLINE_H_
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/PodOperations.h"
+
+namespace mozilla {
+
+/**
+ * Utility class to provide scaling defined in a keySplines element.
+ */
+class SMILKeySpline {
+ public:
+  constexpr SMILKeySpline() : mX1(0), mY1(0), mX2(0), mY2(0) {
+    /* caller must call Init later */\
+  }
+
+    /**
+     * Creates a new key spline control point description.
+     *
+     * aX1, etc. are the x1, y1, x2, y2 cubic Bezier control points as defined
+     * by SMILANIM 3.2.3. They must each be in the range 0.0 <= x <= 1.0
+     */
+    SMILKeySpline(double aX1, double aY1, double aX2, double aY2)
+        : mX1(0), mY1(0), mX2(0), mY2(0) {
+      Init(aX1, aY1, aX2, aY2);
+    }
+
+    double X1() const { return mX1; }
+    double Y1() const { return mY1; }
+    double X2() const { return mX2; }
+    double Y2() const { return mY2; }
+
+    void Init(double aX1, double aY1, double aX2, double aY2);
+
+    /**
+     * Gets the output (y) value for an input (x).
+     *
+     * @param aX  The input x value. A floating-point number between 0 and
+     *            1 (inclusive).
+     */
+    double GetSplineValue(double aX) const;
+
+    void GetSplineDerivativeValues(double aX, double& aDX, double& aDY) const;
+
+    bool operator==(const SMILKeySpline& aOther) const {
+      return mX1 == aOther.mX1 && mY1 == aOther.mY1 && mX2 == aOther.mX2 &&
+             mY2 == aOther.mY2;
+    }
+    bool operator!=(const SMILKeySpline& aOther) const {
+      return !(*this == aOther);
+    }
+    int32_t Compare(const SMILKeySpline& aRhs) const {
+      if (mX1 != aRhs.mX1) return mX1 < aRhs.mX1 ? -1 : 1;
+      if (mY1 != aRhs.mY1) return mY1 < aRhs.mY1 ? -1 : 1;
+      if (mX2 != aRhs.mX2) return mX2 < aRhs.mX2 ? -1 : 1;
+      if (mY2 != aRhs.mY2) return mY2 < aRhs.mY2 ? -1 : 1;
+      return 0;
+    }
+
+   private:
+    void CalcSampleValues();
+
+    /**
+     * Returns x(t) given t, x1, and x2, or y(t) given t, y1, and y2.
+     */
+    static double CalcBezier(double aT, double aA1, double aA2);
+
+    /**
+     * Returns dx/dt given t, x1, and x2, or dy/dt given t, y1, and y2.
+     */
+    static double GetSlope(double aT, double aA1, double aA2);
+
+    double GetTForX(double aX) const;
+
+    double NewtonRaphsonIterate(double aX, double aGuessT) const;
+
+    double BinarySubdivide(double aX, double aA, double aB) const;
+
+    static double A(double aA1, double aA2) {
+      return 1.0 - 3.0 * aA2 + 3.0 * aA1;
+    }
+
+    static double B(double aA1, double aA2) { return 3.0 * aA2 - 6.0 * aA1; }
+
+    static double C(double aA1) { return 3.0 * aA1; }
+
+    double mX1;
+    double mY1;
+    double mX2;
+    double mY2;
+
+    enum { kSplineTableSize = 11 };
+    double mSampleValues[kSplineTableSize] = {};
+
+    static const double kSampleStepSize;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILKEYSPLINE_H_
diff --git a/dom/smil/SMILMilestone.h b/dom/smil/SMILMilestone.h
new file mode 100644
index 0000000000..8b9372428f
--- /dev/null
+++ b/dom/smil/SMILMilestone.h
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILMILESTONE_H_
+#define DOM_SMIL_SMILMILESTONE_H_
+
+#include "mozilla/SMILTypes.h"
+
+namespace mozilla {
+
+/*
+ * A significant moment in an SMILTimedElement's lifetime where a sample is
+ * required.
+ *
+ * Animations register the next milestone in their lifetime with the time
+ * container that they belong to. When the animation controller goes to run
+ * a sample it first visits all the animations that have a registered milestone
+ * in order of their milestone times. This allows interdependencies between
+ * animations to be correctly resolved and events to fire in the proper order.
+ *
+ * A distinction is made between a milestone representing the end of an interval
+ * and any other milestone. This is because if animation A ends at time t, and
+ * animation B begins at the same time t (or has some other significant moment
+ * such as firing a repeat event), SMIL's endpoint-exclusive timing model
+ * implies that the interval end occurs first. In fact, interval ends can be
+ * thought of as ending an infinitesimally small time before t. Therefore,
+ * A should be sampled before B.
+ *
+ * Furthermore, this distinction between sampling the end of an interval and
+ * a regular sample is used within the timing model (specifically in
+ * SMILTimedElement) to ensure that all intervals ending at time t are sampled
+ * before any new intervals are entered so that we have a fully up-to-date set
+ * of instance times available before committing to a new interval. Once an
+ * interval is entered, the begin time is fixed.
+ */
+class SMILMilestone {
+ public:
+  SMILMilestone(SMILTime aTime, bool aIsEnd) : mTime(aTime), mIsEnd(aIsEnd) {}
+
+  SMILMilestone() : mTime(0), mIsEnd(false) {}
+
+  bool operator==(const SMILMilestone& aOther) const {
+    return mTime == aOther.mTime && mIsEnd == aOther.mIsEnd;
+  }
+
+  bool operator!=(const SMILMilestone& aOther) const {
+    return !(*this == aOther);
+  }
+
+  bool operator<(const SMILMilestone& aOther) const {
+    // Earlier times sort first, and for equal times end milestones sort first
+    return mTime < aOther.mTime ||
+           (mTime == aOther.mTime && mIsEnd && !aOther.mIsEnd);
+  }
+
+  bool operator<=(const SMILMilestone& aOther) const {
+    return *this == aOther || *this < aOther;
+  }
+
+  bool operator>=(const SMILMilestone& aOther) const {
+    return !(*this < aOther);
+  }
+
+  SMILTime mTime;  // The milestone time. This may be in container time or
+                   // parent container time depending on where it is used.
+  bool mIsEnd;     // true if this milestone corresponds to an interval
+                   // end, false otherwise.
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILMILESTONE_H_
diff --git a/dom/smil/SMILNullType.cpp b/dom/smil/SMILNullType.cpp
new file mode 100644
index 0000000000..571f6f3afe
--- /dev/null
+++ b/dom/smil/SMILNullType.cpp
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILNullType.h"
+
+#include "mozilla/SMILValue.h"
+#include "nsDebug.h"
+
+namespace mozilla {
+
+/*static*/
+SMILNullType* SMILNullType::Singleton() {
+  static SMILNullType sSingleton;
+  return &sSingleton;
+}
+
+nsresult SMILNullType::Assign(SMILValue& aDest, const SMILValue& aSrc) const {
+  MOZ_ASSERT(aDest.mType == aSrc.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aSrc.mType == this, "Unexpected source type");
+  aDest.mU = aSrc.mU;
+  aDest.mType = Singleton();
+  return NS_OK;
+}
+
+bool SMILNullType::IsEqual(const SMILValue& aLeft,
+                           const SMILValue& aRight) const {
+  MOZ_ASSERT(aLeft.mType == aRight.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aLeft.mType == this, "Unexpected type for SMIL value");
+
+  return true;  // All null-typed values are equivalent.
+}
+
+nsresult SMILNullType::Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+                           uint32_t aCount) const {
+  MOZ_ASSERT_UNREACHABLE("Adding NULL type");
+  return NS_ERROR_FAILURE;
+}
+
+nsresult SMILNullType::ComputeDistance(const SMILValue& aFrom,
+                                       const SMILValue& aTo,
+                                       double& aDistance) const {
+  MOZ_ASSERT_UNREACHABLE("Computing distance for NULL type");
+  return NS_ERROR_FAILURE;
+}
+
+nsresult SMILNullType::Interpolate(const SMILValue& aStartVal,
+                                   const SMILValue& aEndVal,
+                                   double aUnitDistance,
+                                   SMILValue& aResult) const {
+  MOZ_ASSERT_UNREACHABLE("Interpolating NULL type");
+  return NS_ERROR_FAILURE;
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILNullType.h b/dom/smil/SMILNullType.h
new file mode 100644
index 0000000000..83f69b2478
--- /dev/null
+++ b/dom/smil/SMILNullType.h
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILNULLTYPE_H_
+#define DOM_SMIL_SMILNULLTYPE_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILType.h"
+
+namespace mozilla {
+
+class SMILNullType : public SMILType {
+ public:
+  // Singleton for SMILValue objects to hold onto.
+  static SMILNullType* Singleton();
+
+ protected:
+  // SMILType Methods
+  // -------------------
+  void Init(SMILValue& aValue) const override {}
+  void Destroy(SMILValue& aValue) const override {}
+  nsresult Assign(SMILValue& aDest, const SMILValue& aSrc) const override;
+
+  // The remaining methods should never be called, so although they're very
+  // simple they don't need to be inline.
+  bool IsEqual(const SMILValue& aLeft, const SMILValue& aRight) const override;
+  nsresult Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+               uint32_t aCount) const override;
+  nsresult ComputeDistance(const SMILValue& aFrom, const SMILValue& aTo,
+                           double& aDistance) const override;
+  nsresult Interpolate(const SMILValue& aStartVal, const SMILValue& aEndVal,
+                       double aUnitDistance, SMILValue& aResult) const override;
+
+ private:
+  // Private constructor: prevent instances beyond my singleton.
+  constexpr SMILNullType() = default;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILNULLTYPE_H_
diff --git a/dom/smil/SMILParserUtils.cpp b/dom/smil/SMILParserUtils.cpp
new file mode 100644
index 0000000000..948192cc82
--- /dev/null
+++ b/dom/smil/SMILParserUtils.cpp
@@ -0,0 +1,632 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILParserUtils.h"
+
+#include "mozilla/SMILAttr.h"
+#include "mozilla/SMILKeySpline.h"
+#include "mozilla/SMILRepeatCount.h"
+#include "mozilla/SMILTimeValueSpecParams.h"
+#include "mozilla/SMILTypes.h"
+#include "mozilla/SMILValue.h"
+#include "mozilla/SVGContentUtils.h"
+#include "mozilla/TextUtils.h"
+#include "nsContentUtils.h"
+#include "nsCharSeparatedTokenizer.h"
+
+using namespace mozilla::dom;
+//------------------------------------------------------------------------------
+// Helper functions and Constants
+
+namespace {
+
+using namespace mozilla;
+
+const uint32_t MSEC_PER_SEC = 1000;
+const uint32_t MSEC_PER_MIN = 1000 * 60;
+const uint32_t MSEC_PER_HOUR = 1000 * 60 * 60;
+
+#define ACCESSKEY_PREFIX_LC u"accesskey("_ns  // SMIL2+
+#define ACCESSKEY_PREFIX_CC u"accessKey("_ns  // SVG/SMIL ANIM
+#define REPEAT_PREFIX u"repeat("_ns
+#define WALLCLOCK_PREFIX u"wallclock("_ns
+
+inline bool SkipWhitespace(RangedPtr<const char16_t>& aIter,
+                           const RangedPtr<const char16_t>& aEnd) {
+  while (aIter != aEnd) {
+    if (!nsContentUtils::IsHTMLWhitespace(*aIter)) {
+      return true;
+    }
+    ++aIter;
+  }
+  return false;
+}
+
+inline bool ParseColon(RangedPtr<const char16_t>& aIter,
+                       const RangedPtr<const char16_t>& aEnd) {
+  if (aIter == aEnd || *aIter != ':') {
+    return false;
+  }
+  ++aIter;
+  return true;
+}
+
+/*
+ * Exactly two digits in the range 00 - 59 are expected.
+ */
+bool ParseSecondsOrMinutes(RangedPtr<const char16_t>& aIter,
+                           const RangedPtr<const char16_t>& aEnd,
+                           uint32_t& aValue) {
+  if (aIter == aEnd || !mozilla::IsAsciiDigit(*aIter)) {
+    return false;
+  }
+
+  RangedPtr<const char16_t> iter(aIter);
+
+  if (++iter == aEnd || !mozilla::IsAsciiDigit(*iter)) {
+    return false;
+  }
+
+  uint32_t value = 10 * mozilla::AsciiAlphanumericToNumber(*aIter) +
+                   mozilla::AsciiAlphanumericToNumber(*iter);
+  if (value > 59) {
+    return false;
+  }
+  if (++iter != aEnd && mozilla::IsAsciiDigit(*iter)) {
+    return false;
+  }
+
+  aValue = value;
+  aIter = iter;
+  return true;
+}
+
+inline bool ParseClockMetric(RangedPtr<const char16_t>& aIter,
+                             const RangedPtr<const char16_t>& aEnd,
+                             uint32_t& aMultiplier) {
+  if (aIter == aEnd) {
+    aMultiplier = MSEC_PER_SEC;
+    return true;
+  }
+
+  switch (*aIter) {
+    case 'h':
+      if (++aIter == aEnd) {
+        aMultiplier = MSEC_PER_HOUR;
+        return true;
+      }
+      return false;
+    case 'm': {
+      const nsAString& metric = Substring(aIter.get(), aEnd.get());
+      if (metric.EqualsLiteral("min")) {
+        aMultiplier = MSEC_PER_MIN;
+        aIter = aEnd;
+        return true;
+      }
+      if (metric.EqualsLiteral("ms")) {
+        aMultiplier = 1;
+        aIter = aEnd;
+        return true;
+      }
+    }
+      return false;
+    case 's':
+      if (++aIter == aEnd) {
+        aMultiplier = MSEC_PER_SEC;
+        return true;
+      }
+  }
+  return false;
+}
+
+/**
+ * See http://www.w3.org/TR/SVG/animate.html#ClockValueSyntax
+ */
+bool ParseClockValue(RangedPtr<const char16_t>& aIter,
+                     const RangedPtr<const char16_t>& aEnd,
+                     SMILTimeValue::Rounding aRounding,
+                     SMILTimeValue* aResult) {
+  if (aIter == aEnd) {
+    return false;
+  }
+
+  // TIMECOUNT_VALUE     ::= Timecount ("." Fraction)? (Metric)?
+  // PARTIAL_CLOCK_VALUE ::= Minutes ":" Seconds ("." Fraction)?
+  // FULL_CLOCK_VALUE    ::= Hours ":" Minutes ":" Seconds ("." Fraction)?
+  enum ClockType { TIMECOUNT_VALUE, PARTIAL_CLOCK_VALUE, FULL_CLOCK_VALUE };
+
+  int32_t clockType = TIMECOUNT_VALUE;
+
+  RangedPtr<const char16_t> iter(aIter);
+
+  // Determine which type of clock value we have by counting the number
+  // of colons in the string.
+  do {
+    switch (*iter) {
+      case ':':
+        if (clockType == FULL_CLOCK_VALUE) {
+          return false;
+        }
+        ++clockType;
+        break;
+      case 'e':
+      case 'E':
+      case '-':
+      case '+':
+        // Exclude anything invalid (for clock values)
+        // that number parsing might otherwise allow.
+        return false;
+    }
+    ++iter;
+  } while (iter != aEnd);
+
+  iter = aIter;
+
+  int32_t hours = 0, timecount = 0;
+  double fraction = 0.0;
+  uint32_t minutes, seconds, multiplier;
+
+  switch (clockType) {
+    case FULL_CLOCK_VALUE:
+      if (!SVGContentUtils::ParseInteger(iter, aEnd, hours) ||
+          !ParseColon(iter, aEnd)) {
+        return false;
+      }
+      [[fallthrough]];
+    case PARTIAL_CLOCK_VALUE:
+      if (!ParseSecondsOrMinutes(iter, aEnd, minutes) ||
+          !ParseColon(iter, aEnd) ||
+          !ParseSecondsOrMinutes(iter, aEnd, seconds)) {
+        return false;
+      }
+      if (iter != aEnd && (*iter != '.' || !SVGContentUtils::ParseNumber(
+                                               iter, aEnd, fraction))) {
+        return false;
+      }
+      aResult->SetMillis(SMILTime(hours) * MSEC_PER_HOUR +
+                             minutes * MSEC_PER_MIN +
+                             (seconds + fraction) * MSEC_PER_SEC,
+                         aRounding);
+      aIter = iter;
+      return true;
+    case TIMECOUNT_VALUE:
+      if (*iter != '.' &&
+          !SVGContentUtils::ParseInteger(iter, aEnd, timecount)) {
+        return false;
+      }
+      if (iter != aEnd && *iter == '.' &&
+          !SVGContentUtils::ParseNumber(iter, aEnd, fraction)) {
+        return false;
+      }
+      if (!ParseClockMetric(iter, aEnd, multiplier)) {
+        return false;
+      }
+      aResult->SetMillis((timecount + fraction) * multiplier, aRounding);
+      aIter = iter;
+      return true;
+  }
+
+  return false;
+}
+
+bool ParseOffsetValue(RangedPtr<const char16_t>& aIter,
+                      const RangedPtr<const char16_t>& aEnd,
+                      SMILTimeValue* aResult) {
+  RangedPtr<const char16_t> iter(aIter);
+
+  int32_t sign;
+  if (!SVGContentUtils::ParseOptionalSign(iter, aEnd, sign) ||
+      !SkipWhitespace(iter, aEnd) ||
+      !ParseClockValue(iter, aEnd, SMILTimeValue::Rounding::Nearest, aResult)) {
+    return false;
+  }
+  if (sign == -1) {
+    aResult->SetMillis(-aResult->GetMillis());
+  }
+  aIter = iter;
+  return true;
+}
+
+bool ParseOffsetValue(const nsAString& aSpec, SMILTimeValue* aResult) {
+  RangedPtr<const char16_t> iter(SVGContentUtils::GetStartRangedPtr(aSpec));
+  const RangedPtr<const char16_t> end(SVGContentUtils::GetEndRangedPtr(aSpec));
+
+  return ParseOffsetValue(iter, end, aResult) && iter == end;
+}
+
+bool ParseOptionalOffset(RangedPtr<const char16_t>& aIter,
+                         const RangedPtr<const char16_t>& aEnd,
+                         SMILTimeValue* aResult) {
+  if (aIter == aEnd) {
+    *aResult = SMILTimeValue::Zero();
+    return true;
+  }
+
+  return SkipWhitespace(aIter, aEnd) && ParseOffsetValue(aIter, aEnd, aResult);
+}
+
+void MoveToNextToken(RangedPtr<const char16_t>& aIter,
+                     const RangedPtr<const char16_t>& aEnd, bool aBreakOnDot,
+                     bool& aIsAnyCharEscaped) {
+  aIsAnyCharEscaped = false;
+
+  bool isCurrentCharEscaped = false;
+
+  while (aIter != aEnd && !nsContentUtils::IsHTMLWhitespace(*aIter)) {
+    if (isCurrentCharEscaped) {
+      isCurrentCharEscaped = false;
+    } else {
+      if (*aIter == '+' || *aIter == '-' || (aBreakOnDot && *aIter == '.')) {
+        break;
+      }
+      if (*aIter == '\\') {
+        isCurrentCharEscaped = true;
+        aIsAnyCharEscaped = true;
+      }
+    }
+    ++aIter;
+  }
+}
+
+already_AddRefed<nsAtom> ConvertUnescapedTokenToAtom(const nsAString& aToken) {
+  // Whether the token is an id-ref or event-symbol it should be a valid NCName
+  if (aToken.IsEmpty() || NS_FAILED(nsContentUtils::CheckQName(aToken, false)))
+    return nullptr;
+  return NS_Atomize(aToken);
+}
+
+already_AddRefed<nsAtom> ConvertTokenToAtom(const nsAString& aToken,
+                                            bool aUnescapeToken) {
+  // Unescaping involves making a copy of the string which we'd like to avoid if
+  // possible
+  if (!aUnescapeToken) {
+    return ConvertUnescapedTokenToAtom(aToken);
+  }
+
+  nsAutoString token(aToken);
+
+  const char16_t* read = token.BeginReading();
+  const char16_t* const end = token.EndReading();
+  char16_t* write = token.BeginWriting();
+  bool escape = false;
+
+  while (read != end) {
+    MOZ_ASSERT(write <= read, "Writing past where we've read");
+    if (!escape && *read == '\\') {
+      escape = true;
+      ++read;
+    } else {
+      *write++ = *read++;
+      escape = false;
+    }
+  }
+  token.Truncate(write - token.BeginReading());
+
+  return ConvertUnescapedTokenToAtom(token);
+}
+
+bool ParseElementBaseTimeValueSpec(const nsAString& aSpec,
+                                   SMILTimeValueSpecParams& aResult) {
+  SMILTimeValueSpecParams result;
+
+  //
+  // The spec will probably look something like one of these
+  //
+  // element-name.begin
+  // element-name.event-name
+  // event-name
+  // element-name.repeat(3)
+  // event\.name
+  //
+  // Technically `repeat(3)' is permitted but the behaviour in this case is not
+  // defined (for SMIL Animation) so we don't support it here.
+  //
+
+  RangedPtr<const char16_t> start(SVGContentUtils::GetStartRangedPtr(aSpec));
+  RangedPtr<const char16_t> end(SVGContentUtils::GetEndRangedPtr(aSpec));
+
+  if (start == end) {
+    return false;
+  }
+
+  RangedPtr<const char16_t> tokenEnd(start);
+
+  bool requiresUnescaping;
+  MoveToNextToken(tokenEnd, end, true, requiresUnescaping);
+
+  RefPtr<nsAtom> atom = ConvertTokenToAtom(
+      Substring(start.get(), tokenEnd.get()), requiresUnescaping);
+  if (atom == nullptr) {
+    return false;
+  }
+
+  // Parse the second token if there is one
+  if (tokenEnd != end && *tokenEnd == '.') {
+    result.mDependentElemID = atom;
+
+    ++tokenEnd;
+    start = tokenEnd;
+    MoveToNextToken(tokenEnd, end, false, requiresUnescaping);
+
+    const nsAString& token2 = Substring(start.get(), tokenEnd.get());
+
+    // element-name.begin
+    if (token2.EqualsLiteral("begin")) {
+      result.mType = SMILTimeValueSpecParams::SYNCBASE;
+      result.mSyncBegin = true;
+      // element-name.end
+    } else if (token2.EqualsLiteral("end")) {
+      result.mType = SMILTimeValueSpecParams::SYNCBASE;
+      result.mSyncBegin = false;
+      // element-name.repeat(digit+)
+    } else if (StringBeginsWith(token2, REPEAT_PREFIX)) {
+      start += REPEAT_PREFIX.Length();
+      int32_t repeatValue;
+      if (start == tokenEnd || *start == '+' || *start == '-' ||
+          !SVGContentUtils::ParseInteger(start, tokenEnd, repeatValue)) {
+        return false;
+      }
+      if (start == tokenEnd || *start != ')') {
+        return false;
+      }
+      result.mType = SMILTimeValueSpecParams::REPEAT;
+      result.mRepeatIteration = repeatValue;
+      // element-name.event-symbol
+    } else {
+      atom = ConvertTokenToAtom(token2, requiresUnescaping);
+      if (atom == nullptr) {
+        return false;
+      }
+      result.mType = SMILTimeValueSpecParams::EVENT;
+      result.mEventSymbol = atom;
+    }
+  } else {
+    // event-symbol
+    result.mType = SMILTimeValueSpecParams::EVENT;
+    result.mEventSymbol = atom;
+  }
+
+  // We've reached the end of the token, so we should now be either looking at
+  // a '+', '-' (possibly with whitespace before it), or the end.
+  if (!ParseOptionalOffset(tokenEnd, end, &result.mOffset) || tokenEnd != end) {
+    return false;
+  }
+  aResult = result;
+  return true;
+}
+
+}  // namespace
+
+namespace mozilla {
+
+//------------------------------------------------------------------------------
+// Implementation
+
+const nsDependentSubstring SMILParserUtils::TrimWhitespace(
+    const nsAString& aString) {
+  nsAString::const_iterator start, end;
+
+  aString.BeginReading(start);
+  aString.EndReading(end);
+
+  // Skip whitespace characters at the beginning
+  while (start != end && nsContentUtils::IsHTMLWhitespace(*start)) {
+    ++start;
+  }
+
+  // Skip whitespace characters at the end.
+  while (end != start) {
+    --end;
+
+    if (!nsContentUtils::IsHTMLWhitespace(*end)) {
+      // Step back to the last non-whitespace character.
+      ++end;
+
+      break;
+    }
+  }
+
+  return Substring(start, end);
+}
+
+bool SMILParserUtils::ParseKeySplines(
+    const nsAString& aSpec, FallibleTArray<SMILKeySpline>& aKeySplines) {
+  for (const auto& controlPoint :
+       nsCharSeparatedTokenizerTemplate<nsContentUtils::IsHTMLWhitespace>(aSpec,
+                                                                          ';')
+           .ToRange()) {
+    nsCharSeparatedTokenizerTemplate<nsContentUtils::IsHTMLWhitespace,
+                                     nsTokenizerFlags::SeparatorOptional>
+        tokenizer(controlPoint, ',');
+
+    double values[4];
+    for (auto& value : values) {
+      if (!tokenizer.hasMoreTokens() ||
+          !SVGContentUtils::ParseNumber(tokenizer.nextToken(), value) ||
+          value > 1.0 || value < 0.0) {
+        return false;
+      }
+    }
+    if (tokenizer.hasMoreTokens() || tokenizer.separatorAfterCurrentToken() ||
+        !aKeySplines.AppendElement(
+            SMILKeySpline(values[0], values[1], values[2], values[3]),
+            fallible)) {
+      return false;
+    }
+  }
+
+  return !aKeySplines.IsEmpty();
+}
+
+bool SMILParserUtils::ParseSemicolonDelimitedProgressList(
+    const nsAString& aSpec, bool aNonDecreasing,
+    FallibleTArray<double>& aArray) {
+  nsCharSeparatedTokenizerTemplate<nsContentUtils::IsHTMLWhitespace> tokenizer(
+      aSpec, ';');
+
+  double previousValue = -1.0;
+
+  while (tokenizer.hasMoreTokens()) {
+    double value;
+    if (!SVGContentUtils::ParseNumber(tokenizer.nextToken(), value)) {
+      return false;
+    }
+
+    if (value > 1.0 || value < 0.0 ||
+        (aNonDecreasing && value < previousValue)) {
+      return false;
+    }
+
+    if (!aArray.AppendElement(value, fallible)) {
+      return false;
+    }
+    previousValue = value;
+  }
+
+  return !aArray.IsEmpty();
+}
+
+// Helper class for ParseValues
+class MOZ_STACK_CLASS SMILValueParser
+    : public SMILParserUtils::GenericValueParser {
+ public:
+  SMILValueParser(const SVGAnimationElement* aSrcElement,
+                  const SMILAttr* aSMILAttr,
+                  FallibleTArray<SMILValue>* aValuesArray,
+                  bool* aPreventCachingOfSandwich)
+      : mSrcElement(aSrcElement),
+        mSMILAttr(aSMILAttr),
+        mValuesArray(aValuesArray),
+        mPreventCachingOfSandwich(aPreventCachingOfSandwich) {}
+
+  bool Parse(const nsAString& aValueStr) override {
+    SMILValue newValue;
+    if (NS_FAILED(mSMILAttr->ValueFromString(aValueStr, mSrcElement, newValue,
+                                             *mPreventCachingOfSandwich)))
+      return false;
+
+    if (!mValuesArray->AppendElement(newValue, fallible)) {
+      return false;
+    }
+    return true;
+  }
+
+ protected:
+  const SVGAnimationElement* mSrcElement;
+  const SMILAttr* mSMILAttr;
+  FallibleTArray<SMILValue>* mValuesArray;
+  bool* mPreventCachingOfSandwich;
+};
+
+bool SMILParserUtils::ParseValues(const nsAString& aSpec,
+                                  const SVGAnimationElement* aSrcElement,
+                                  const SMILAttr& aAttribute,
+                                  FallibleTArray<SMILValue>& aValuesArray,
+                                  bool& aPreventCachingOfSandwich) {
+  // Assume all results can be cached, until we find one that can't.
+  aPreventCachingOfSandwich = false;
+  SMILValueParser valueParser(aSrcElement, &aAttribute, &aValuesArray,
+                              &aPreventCachingOfSandwich);
+  return ParseValuesGeneric(aSpec, valueParser);
+}
+
+bool SMILParserUtils::ParseValuesGeneric(const nsAString& aSpec,
+                                         GenericValueParser& aParser) {
+  nsCharSeparatedTokenizerTemplate<nsContentUtils::IsHTMLWhitespace> tokenizer(
+      aSpec, ';');
+  if (!tokenizer.hasMoreTokens()) {  // Empty list
+    return false;
+  }
+
+  while (tokenizer.hasMoreTokens()) {
+    if (!aParser.Parse(tokenizer.nextToken())) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool SMILParserUtils::ParseRepeatCount(const nsAString& aSpec,
+                                       SMILRepeatCount& aResult) {
+  const nsAString& spec = SMILParserUtils::TrimWhitespace(aSpec);
+
+  if (spec.EqualsLiteral("indefinite")) {
+    aResult.SetIndefinite();
+    return true;
+  }
+
+  double value;
+  if (!SVGContentUtils::ParseNumber(spec, value) || value <= 0.0) {
+    return false;
+  }
+  aResult = value;
+  return true;
+}
+
+bool SMILParserUtils::ParseTimeValueSpecParams(
+    const nsAString& aSpec, SMILTimeValueSpecParams& aResult) {
+  const nsAString& spec = TrimWhitespace(aSpec);
+
+  if (spec.EqualsLiteral("indefinite")) {
+    aResult.mType = SMILTimeValueSpecParams::INDEFINITE;
+    return true;
+  }
+
+  // offset type
+  if (ParseOffsetValue(spec, &aResult.mOffset)) {
+    aResult.mType = SMILTimeValueSpecParams::OFFSET;
+    return true;
+  }
+
+  // wallclock type
+  if (StringBeginsWith(spec, WALLCLOCK_PREFIX)) {
+    return false;  // Wallclock times not implemented
+  }
+
+  // accesskey type
+  if (StringBeginsWith(spec, ACCESSKEY_PREFIX_LC) ||
+      StringBeginsWith(spec, ACCESSKEY_PREFIX_CC)) {
+    return false;  // accesskey is not supported
+  }
+
+  // event, syncbase, or repeat
+  return ParseElementBaseTimeValueSpec(spec, aResult);
+}
+
+bool SMILParserUtils::ParseClockValue(const nsAString& aSpec,
+                                      SMILTimeValue::Rounding aRounding,
+                                      SMILTimeValue* aResult) {
+  RangedPtr<const char16_t> iter(SVGContentUtils::GetStartRangedPtr(aSpec));
+  RangedPtr<const char16_t> end(SVGContentUtils::GetEndRangedPtr(aSpec));
+
+  return ::ParseClockValue(iter, end, aRounding, aResult) && iter == end;
+}
+
+int32_t SMILParserUtils::CheckForNegativeNumber(const nsAString& aStr) {
+  int32_t absValLocation = -1;
+
+  RangedPtr<const char16_t> start(SVGContentUtils::GetStartRangedPtr(aStr));
+  RangedPtr<const char16_t> iter = start;
+  RangedPtr<const char16_t> end(SVGContentUtils::GetEndRangedPtr(aStr));
+
+  // Skip initial whitespace
+  while (iter != end && nsContentUtils::IsHTMLWhitespace(*iter)) {
+    ++iter;
+  }
+
+  // Check for dash
+  if (iter != end && *iter == '-') {
+    ++iter;
+    // Check for numeric character
+    if (iter != end && mozilla::IsAsciiDigit(*iter)) {
+      absValLocation = iter - start;
+    }
+  }
+  return absValLocation;
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILParserUtils.h b/dom/smil/SMILParserUtils.h
new file mode 100644
index 0000000000..f1ac4ba51d
--- /dev/null
+++ b/dom/smil/SMILParserUtils.h
@@ -0,0 +1,91 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILPARSERUTILS_H_
+#define DOM_SMIL_SMILPARSERUTILS_H_
+
+#include "nsTArray.h"
+#include "nsStringFwd.h"
+#include "SMILTimeValue.h"
+
+namespace mozilla {
+
+class SMILAttr;
+class SMILKeySpline;
+class SMILRepeatCount;
+class SMILTimeValueSpecParams;
+class SMILValue;
+
+namespace dom {
+class SVGAnimationElement;
+}  // namespace dom
+
+/**
+ * Common parsing utilities for the SMIL module. There is little re-use here; it
+ * simply serves to simplify other classes by moving parsing outside and to aid
+ * unit testing.
+ */
+class SMILParserUtils {
+ public:
+  // Abstract helper-class for assisting in parsing |values| attribute
+  class MOZ_STACK_CLASS GenericValueParser {
+   public:
+    virtual bool Parse(const nsAString& aValueStr) = 0;
+  };
+
+  static const nsDependentSubstring TrimWhitespace(const nsAString& aString);
+
+  static bool ParseKeySplines(const nsAString& aSpec,
+                              FallibleTArray<SMILKeySpline>& aKeySplines);
+
+  // Used for parsing the |keyTimes| and |keyPoints| attributes.
+  static bool ParseSemicolonDelimitedProgressList(
+      const nsAString& aSpec, bool aNonDecreasing,
+      FallibleTArray<double>& aArray);
+
+  static bool ParseValues(const nsAString& aSpec,
+                          const mozilla::dom::SVGAnimationElement* aSrcElement,
+                          const SMILAttr& aAttribute,
+                          FallibleTArray<SMILValue>& aValuesArray,
+                          bool& aPreventCachingOfSandwich);
+
+  // Generic method that will run some code on each sub-section of an animation
+  // element's "values" list.
+  static bool ParseValuesGeneric(const nsAString& aSpec,
+                                 GenericValueParser& aParser);
+
+  static bool ParseRepeatCount(const nsAString& aSpec,
+                               SMILRepeatCount& aResult);
+
+  static bool ParseTimeValueSpecParams(const nsAString& aSpec,
+                                       SMILTimeValueSpecParams& aResult);
+
+  /*
+   * Parses a clock value as defined in the SMIL Animation specification.
+   * If parsing succeeds the returned value will be a non-negative, definite
+   * time value i.e. IsDefinite will return true.
+   *
+   * @param aSpec    The string containing a clock value, e.g. "10s"
+   * @param aResult  The parsed result. [OUT]
+   * @return true if parsing succeeded, otherwise false.
+   */
+  static bool ParseClockValue(const nsAString& aSpec,
+                              SMILTimeValue::Rounding aRounding,
+                              SMILTimeValue* aResult);
+
+  /*
+   * This method checks whether the given string looks like a negative number.
+   * Specifically, it checks whether the string looks matches the pattern
+   * "[whitespace]*-[numeral].*" If the string matches this pattern, this
+   * method returns the index of the first character after the '-' sign
+   * (i.e. the index of the absolute value).  If not, this method returns -1.
+   */
+  static int32_t CheckForNegativeNumber(const nsAString& aStr);
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILPARSERUTILS_H_
diff --git a/dom/smil/SMILRepeatCount.cpp b/dom/smil/SMILRepeatCount.cpp
new file mode 100644
index 0000000000..9a56a42d45
--- /dev/null
+++ b/dom/smil/SMILRepeatCount.cpp
@@ -0,0 +1,14 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILRepeatCount.h"
+
+namespace mozilla {
+
+/*static*/ const double SMILRepeatCount::kNotSet = -1.0;
+/*static*/ const double SMILRepeatCount::kIndefinite = -2.0;
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILRepeatCount.h b/dom/smil/SMILRepeatCount.h
new file mode 100644
index 0000000000..0b93aae994
--- /dev/null
+++ b/dom/smil/SMILRepeatCount.h
@@ -0,0 +1,62 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILREPEATCOUNT_H_
+#define DOM_SMIL_SMILREPEATCOUNT_H_
+
+#include "nsDebug.h"
+#include <math.h>
+
+namespace mozilla {
+
+//----------------------------------------------------------------------
+// SMILRepeatCount
+//
+// A tri-state non-negative floating point number for representing the number of
+// times an animation repeat, i.e. the SMIL repeatCount attribute.
+//
+// The three states are:
+//  1. not-set
+//  2. set (with non-negative, non-zero count value)
+//  3. indefinite
+//
+class SMILRepeatCount {
+ public:
+  SMILRepeatCount() : mCount(kNotSet) {}
+  explicit SMILRepeatCount(double aCount) : mCount(kNotSet) {
+    SetCount(aCount);
+  }
+
+  operator double() const {
+    MOZ_ASSERT(IsDefinite(),
+               "Converting indefinite or unset repeat count to double");
+    return mCount;
+  }
+  bool IsDefinite() const { return mCount != kNotSet && mCount != kIndefinite; }
+  bool IsIndefinite() const { return mCount == kIndefinite; }
+  bool IsSet() const { return mCount != kNotSet; }
+
+  SMILRepeatCount& operator=(double aCount) {
+    SetCount(aCount);
+    return *this;
+  }
+  void SetCount(double aCount) {
+    NS_ASSERTION(aCount > 0.0, "Negative or zero repeat count");
+    mCount = aCount > 0.0 ? aCount : kNotSet;
+  }
+  void SetIndefinite() { mCount = kIndefinite; }
+  void Unset() { mCount = kNotSet; }
+
+ private:
+  static const double kNotSet;
+  static const double kIndefinite;
+
+  double mCount;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILREPEATCOUNT_H_
diff --git a/dom/smil/SMILSetAnimationFunction.cpp b/dom/smil/SMILSetAnimationFunction.cpp
new file mode 100644
index 0000000000..0ef19a2faa
--- /dev/null
+++ b/dom/smil/SMILSetAnimationFunction.cpp
@@ -0,0 +1,26 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILSetAnimationFunction.h"
+
+namespace mozilla {
+
+bool SMILSetAnimationFunction::IsDisallowedAttribute(
+    const nsAtom* aAttribute) const {
+  //
+  // A <set> element is similar to <animate> but lacks:
+  //   AnimationValue.attrib(calcMode, values, keyTimes, keySplines, from, to,
+  //                         by) -- BUT has 'to'
+  //   AnimationAddition.attrib(additive, accumulate)
+  //
+  return aAttribute == nsGkAtoms::calcMode || aAttribute == nsGkAtoms::values ||
+         aAttribute == nsGkAtoms::keyTimes ||
+         aAttribute == nsGkAtoms::keySplines || aAttribute == nsGkAtoms::from ||
+         aAttribute == nsGkAtoms::by || aAttribute == nsGkAtoms::additive ||
+         aAttribute == nsGkAtoms::accumulate;
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILSetAnimationFunction.h b/dom/smil/SMILSetAnimationFunction.h
new file mode 100644
index 0000000000..79e94d1e47
--- /dev/null
+++ b/dom/smil/SMILSetAnimationFunction.h
@@ -0,0 +1,38 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILSETANIMATIONFUNCTION_H_
+#define DOM_SMIL_SMILSETANIMATIONFUNCTION_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILAnimationFunction.h"
+
+namespace mozilla {
+
+//----------------------------------------------------------------------
+// SMILSetAnimationFunction
+//
+// Subclass of SMILAnimationFunction that limits the behaviour to that offered
+// by a <set> element.
+//
+class SMILSetAnimationFunction : public SMILAnimationFunction {
+ protected:
+  bool IsDisallowedAttribute(const nsAtom* aAttribute) const override;
+
+  // Although <set> animation might look like to-animation, unlike to-animation,
+  // it never interpolates values.
+  // Returning false here will mean this animation function gets treated as
+  // a single-valued function and no interpolation will be attempted.
+  bool IsToAnimation() const override { return false; }
+
+  // <set> applies the exact same value across the simple duration.
+  bool IsValueFixedForSimpleDuration() const override { return true; }
+  bool WillReplace() const override { return true; }
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILSETANIMATIONFUNCTION_H_
diff --git a/dom/smil/SMILStringType.cpp b/dom/smil/SMILStringType.cpp
new file mode 100644
index 0000000000..a79a97eb2c
--- /dev/null
+++ b/dom/smil/SMILStringType.cpp
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILStringType.h"
+
+#include "mozilla/SMILValue.h"
+#include "nsDebug.h"
+#include "nsString.h"
+
+namespace mozilla {
+
+void SMILStringType::Init(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.IsNull(), "Unexpected value type");
+  aValue.mU.mPtr = new nsString();
+  aValue.mType = this;
+}
+
+void SMILStringType::Destroy(SMILValue& aValue) const {
+  MOZ_ASSERT(aValue.mType == this, "Unexpected SMIL value");
+  delete static_cast<nsAString*>(aValue.mU.mPtr);
+  aValue.mU.mPtr = nullptr;
+  aValue.mType = SMILNullType::Singleton();
+}
+
+nsresult SMILStringType::Assign(SMILValue& aDest, const SMILValue& aSrc) const {
+  MOZ_ASSERT(aDest.mType == aSrc.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aDest.mType == this, "Unexpected SMIL value");
+
+  const nsAString* src = static_cast<const nsAString*>(aSrc.mU.mPtr);
+  nsAString* dst = static_cast<nsAString*>(aDest.mU.mPtr);
+  *dst = *src;
+  return NS_OK;
+}
+
+bool SMILStringType::IsEqual(const SMILValue& aLeft,
+                             const SMILValue& aRight) const {
+  MOZ_ASSERT(aLeft.mType == aRight.mType, "Incompatible SMIL types");
+  MOZ_ASSERT(aLeft.mType == this, "Unexpected type for SMIL value");
+
+  const nsAString* leftString = static_cast<const nsAString*>(aLeft.mU.mPtr);
+  const nsAString* rightString = static_cast<nsAString*>(aRight.mU.mPtr);
+  return *leftString == *rightString;
+}
+
+nsresult SMILStringType::Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+                             uint32_t aCount) const {
+  MOZ_ASSERT(aValueToAdd.mType == aDest.mType, "Trying to add invalid types");
+  MOZ_ASSERT(aValueToAdd.mType == this, "Unexpected source type");
+  return NS_ERROR_FAILURE;  // string values can't be added to each other
+}
+
+nsresult SMILStringType::ComputeDistance(const SMILValue& aFrom,
+                                         const SMILValue& aTo,
+                                         double& aDistance) const {
+  MOZ_ASSERT(aFrom.mType == aTo.mType, "Trying to compare different types");
+  MOZ_ASSERT(aFrom.mType == this, "Unexpected source type");
+  return NS_ERROR_FAILURE;  // there is no concept of distance between string
+                            // values
+}
+
+nsresult SMILStringType::Interpolate(const SMILValue& aStartVal,
+                                     const SMILValue& aEndVal,
+                                     double aUnitDistance,
+                                     SMILValue& aResult) const {
+  MOZ_ASSERT(aStartVal.mType == aEndVal.mType,
+             "Trying to interpolate different types");
+  MOZ_ASSERT(aStartVal.mType == this, "Unexpected types for interpolation");
+  MOZ_ASSERT(aResult.mType == this, "Unexpected result type");
+  return NS_ERROR_FAILURE;  // string values do not interpolate
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILStringType.h b/dom/smil/SMILStringType.h
new file mode 100644
index 0000000000..7d33d6dade
--- /dev/null
+++ b/dom/smil/SMILStringType.h
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILSTRINGTYPE_H_
+#define DOM_SMIL_SMILSTRINGTYPE_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILType.h"
+
+namespace mozilla {
+
+class SMILStringType : public SMILType {
+ public:
+  // Singleton for SMILValue objects to hold onto.
+  static SMILStringType* Singleton() {
+    static SMILStringType sSingleton;
+    return &sSingleton;
+  }
+
+ protected:
+  // SMILType Methods
+  // -------------------
+  void Init(SMILValue& aValue) const override;
+  void Destroy(SMILValue& aValue) const override;
+  nsresult Assign(SMILValue& aDest, const SMILValue& aSrc) const override;
+  bool IsEqual(const SMILValue& aLeft, const SMILValue& aRight) const override;
+  nsresult Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+               uint32_t aCount) const override;
+  nsresult ComputeDistance(const SMILValue& aFrom, const SMILValue& aTo,
+                           double& aDistance) const override;
+  nsresult Interpolate(const SMILValue& aStartVal, const SMILValue& aEndVal,
+                       double aUnitDistance, SMILValue& aResult) const override;
+
+ private:
+  // Private constructor: prevent instances beyond my singleton.
+  constexpr SMILStringType() = default;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILSTRINGTYPE_H_
diff --git a/dom/smil/SMILTargetIdentifier.h b/dom/smil/SMILTargetIdentifier.h
new file mode 100644
index 0000000000..14a2ee3152
--- /dev/null
+++ b/dom/smil/SMILTargetIdentifier.h
@@ -0,0 +1,87 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILTARGETIDENTIFIER_H_
+#define DOM_SMIL_SMILTARGETIDENTIFIER_H_
+
+// XXX Avoid including this here by moving function bodies to the cpp file
+#include "nsAtom.h"
+#include "nsIContent.h"
+#include "mozilla/dom/Element.h"
+
+class nsIContent;
+
+namespace mozilla {
+namespace dom {
+class Element;
+}
+
+/**
+ * Struct: SMILTargetIdentifier
+ *
+ * Tuple of: { Animated Element, Attribute Name }
+ *
+ * Used in SMILAnimationController as hash key for mapping an animation
+ * target to the SMILCompositor for that target.
+ *
+ * NOTE: Need a nsRefPtr for the element & attribute name, because
+ * SMILAnimationController retain its hash table for one sample into the
+ * future, and we need to make sure their target isn't deleted in that time.
+ */
+
+struct SMILTargetIdentifier {
+  SMILTargetIdentifier()
+      : mElement(nullptr),
+        mAttributeName(nullptr),
+        mAttributeNamespaceID(kNameSpaceID_Unknown) {}
+
+  inline bool Equals(const SMILTargetIdentifier& aOther) const {
+    return (aOther.mElement == mElement &&
+            aOther.mAttributeName == mAttributeName &&
+            aOther.mAttributeNamespaceID == mAttributeNamespaceID);
+  }
+
+  RefPtr<mozilla::dom::Element> mElement;
+  RefPtr<nsAtom> mAttributeName;
+  int32_t mAttributeNamespaceID;
+};
+
+/**
+ * Class: SMILWeakTargetIdentifier
+ *
+ * Version of the above struct that uses non-owning pointers.  These are kept
+ * private, to ensure that they aren't ever dereferenced (or used at all,
+ * outside of Equals()).
+ *
+ * This is solely for comparisons to determine if a target has changed
+ * from one sample to the next.
+ */
+class SMILWeakTargetIdentifier {
+ public:
+  // Trivial constructor
+  SMILWeakTargetIdentifier() : mElement(nullptr), mAttributeName(nullptr) {}
+
+  // Allow us to update a weak identifier to match a given non-weak identifier
+  SMILWeakTargetIdentifier& operator=(const SMILTargetIdentifier& aOther) {
+    mElement = aOther.mElement;
+    mAttributeName = aOther.mAttributeName;
+    return *this;
+  }
+
+  // Allow for comparison vs. non-weak identifier
+  inline bool Equals(const SMILTargetIdentifier& aOther) const {
+    return (aOther.mElement == mElement &&
+            aOther.mAttributeName == mAttributeName);
+  }
+
+ private:
+  const nsIContent* mElement;
+  const nsAtom* mAttributeName;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILTARGETIDENTIFIER_H_
diff --git a/dom/smil/SMILTimeContainer.cpp b/dom/smil/SMILTimeContainer.cpp
new file mode 100644
index 0000000000..321c27ed2c
--- /dev/null
+++ b/dom/smil/SMILTimeContainer.cpp
@@ -0,0 +1,306 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILTimeContainer.h"
+
+#include "mozilla/AutoRestore.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/SMILTimedElement.h"
+#include "mozilla/SMILTimeValue.h"
+#include <algorithm>
+
+namespace mozilla {
+
+SMILTimeContainer::SMILTimeContainer()
+    : mParent(nullptr),
+      mCurrentTime(0L),
+      mParentOffset(0L),
+      mPauseStart(0L),
+      mNeedsPauseSample(false),
+      mNeedsRewind(false),
+      mIsSeeking(false),
+#ifdef DEBUG
+      mHoldingEntries(false),
+#endif
+      mPauseState(PAUSE_BEGIN) {
+}
+
+SMILTimeContainer::~SMILTimeContainer() {
+  if (mParent) {
+    mParent->RemoveChild(*this);
+  }
+}
+
+SMILTimeValue SMILTimeContainer::ContainerToParentTime(
+    SMILTime aContainerTime) const {
+  // If we're paused, then future times are indefinite
+  if (IsPaused() && aContainerTime > mCurrentTime)
+    return SMILTimeValue::Indefinite();
+
+  return SMILTimeValue(aContainerTime + mParentOffset);
+}
+
+SMILTimeValue SMILTimeContainer::ParentToContainerTime(
+    SMILTime aParentTime) const {
+  // If we're paused, then any time after when we paused is indefinite
+  if (IsPaused() && aParentTime > mPauseStart)
+    return SMILTimeValue::Indefinite();
+
+  return SMILTimeValue(aParentTime - mParentOffset);
+}
+
+void SMILTimeContainer::Begin() {
+  Resume(PAUSE_BEGIN);
+  if (mPauseState) {
+    mNeedsPauseSample = true;
+  }
+
+  // This is a little bit complicated here. Ideally we'd just like to call
+  // Sample() and force an initial sample but this turns out to be a bad idea
+  // because this may mean that NeedsSample() no longer reports true and so when
+  // we come to the first real sample our parent will skip us over altogether.
+  // So we force the time to be updated and adopt the policy to never call
+  // Sample() ourselves but to always leave that to our parent or client.
+
+  UpdateCurrentTime();
+}
+
+void SMILTimeContainer::Pause(uint32_t aType) {
+  bool didStartPause = false;
+
+  if (!mPauseState && aType) {
+    mPauseStart = GetParentTime();
+    mNeedsPauseSample = true;
+    didStartPause = true;
+  }
+
+  mPauseState |= aType;
+
+  if (didStartPause) {
+    NotifyTimeChange();
+  }
+}
+
+void SMILTimeContainer::Resume(uint32_t aType) {
+  if (!mPauseState) return;
+
+  mPauseState &= ~aType;
+
+  if (!mPauseState) {
+    SMILTime extraOffset = GetParentTime() - mPauseStart;
+    mParentOffset += extraOffset;
+    NotifyTimeChange();
+  }
+}
+
+SMILTime SMILTimeContainer::GetCurrentTimeAsSMILTime() const {
+  // The following behaviour is consistent with:
+  // http://www.w3.org/2003/01/REC-SVG11-20030114-errata
+  //  #getCurrentTime_setCurrentTime_undefined_before_document_timeline_begin
+  // which says that if GetCurrentTime is called before the document timeline
+  // has begun we should just return 0.
+  if (IsPausedByType(PAUSE_BEGIN)) return 0L;
+
+  return mCurrentTime;
+}
+
+void SMILTimeContainer::SetCurrentTime(SMILTime aSeekTo) {
+  // SVG 1.1 doesn't specify what to do for negative times so we adopt SVGT1.2's
+  // behaviour of clamping negative times to 0.
+  aSeekTo = std::max<SMILTime>(0, aSeekTo);
+
+  // The following behaviour is consistent with:
+  // http://www.w3.org/2003/01/REC-SVG11-20030114-errata
+  //  #getCurrentTime_setCurrentTime_undefined_before_document_timeline_begin
+  // which says that if SetCurrentTime is called before the document timeline
+  // has begun we should still adjust the offset.
+  SMILTime parentTime = GetParentTime();
+  mParentOffset = parentTime - aSeekTo;
+  mIsSeeking = true;
+
+  if (IsPaused()) {
+    mNeedsPauseSample = true;
+    mPauseStart = parentTime;
+  }
+
+  if (aSeekTo < mCurrentTime) {
+    // Backwards seek
+    mNeedsRewind = true;
+    ClearMilestones();
+  }
+
+  // Force an update to the current time in case we get a call to GetCurrentTime
+  // before another call to Sample().
+  UpdateCurrentTime();
+
+  NotifyTimeChange();
+}
+
+SMILTime SMILTimeContainer::GetParentTime() const {
+  if (mParent) return mParent->GetCurrentTimeAsSMILTime();
+
+  return 0L;
+}
+
+void SMILTimeContainer::SyncPauseTime() {
+  if (IsPaused()) {
+    SMILTime parentTime = GetParentTime();
+    SMILTime extraOffset = parentTime - mPauseStart;
+    mParentOffset += extraOffset;
+    mPauseStart = parentTime;
+  }
+}
+
+void SMILTimeContainer::Sample() {
+  if (!NeedsSample()) return;
+
+  UpdateCurrentTime();
+  DoSample();
+
+  mNeedsPauseSample = false;
+}
+
+nsresult SMILTimeContainer::SetParent(SMILTimeContainer* aParent) {
+  if (mParent) {
+    mParent->RemoveChild(*this);
+    // When we're not attached to a parent time container, GetParentTime() will
+    // return 0. We need to adjust our pause state information to be relative to
+    // this new time base.
+    // Note that since "current time = parent time - parent offset" setting the
+    // parent offset and pause start as follows preserves our current time even
+    // while parent time = 0.
+    mParentOffset = -mCurrentTime;
+    mPauseStart = 0L;
+  }
+
+  mParent = aParent;
+
+  nsresult rv = NS_OK;
+  if (mParent) {
+    rv = mParent->AddChild(*this);
+  }
+
+  return rv;
+}
+
+void SMILTimeContainer::AddMilestone(
+    const SMILMilestone& aMilestone,
+    mozilla::dom::SVGAnimationElement& aElement) {
+  // We record the milestone time and store it along with the element but this
+  // time may change (e.g. if attributes are changed on the timed element in
+  // between samples). If this happens, then we may do an unecessary sample
+  // but that's pretty cheap.
+  MOZ_ASSERT(!mHoldingEntries);
+  mMilestoneEntries.Push(MilestoneEntry(aMilestone, aElement));
+}
+
+void SMILTimeContainer::ClearMilestones() {
+  MOZ_ASSERT(!mHoldingEntries);
+  mMilestoneEntries.Clear();
+}
+
+bool SMILTimeContainer::GetNextMilestoneInParentTime(
+    SMILMilestone& aNextMilestone) const {
+  if (mMilestoneEntries.IsEmpty()) return false;
+
+  SMILTimeValue parentTime =
+      ContainerToParentTime(mMilestoneEntries.Top().mMilestone.mTime);
+  if (!parentTime.IsDefinite()) return false;
+
+  aNextMilestone = SMILMilestone(parentTime.GetMillis(),
+                                 mMilestoneEntries.Top().mMilestone.mIsEnd);
+
+  return true;
+}
+
+bool SMILTimeContainer::PopMilestoneElementsAtMilestone(
+    const SMILMilestone& aMilestone, AnimElemArray& aMatchedElements) {
+  if (mMilestoneEntries.IsEmpty()) return false;
+
+  SMILTimeValue containerTime = ParentToContainerTime(aMilestone.mTime);
+  if (!containerTime.IsDefinite()) return false;
+
+  SMILMilestone containerMilestone(containerTime.GetMillis(),
+                                   aMilestone.mIsEnd);
+
+  MOZ_ASSERT(mMilestoneEntries.Top().mMilestone >= containerMilestone,
+             "Trying to pop off earliest times but we have earlier ones that "
+             "were overlooked");
+
+  MOZ_ASSERT(!mHoldingEntries);
+
+  bool gotOne = false;
+  while (!mMilestoneEntries.IsEmpty() &&
+         mMilestoneEntries.Top().mMilestone == containerMilestone) {
+    aMatchedElements.AppendElement(mMilestoneEntries.Pop().mTimebase);
+    gotOne = true;
+  }
+
+  return gotOne;
+}
+
+void SMILTimeContainer::Traverse(
+    nsCycleCollectionTraversalCallback* aCallback) {
+#ifdef DEBUG
+  AutoRestore<bool> saveHolding(mHoldingEntries);
+  mHoldingEntries = true;
+#endif
+  const MilestoneEntry* p = mMilestoneEntries.Elements();
+  while (p < mMilestoneEntries.Elements() + mMilestoneEntries.Length()) {
+    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(*aCallback, "mTimebase");
+    aCallback->NoteXPCOMChild(static_cast<nsIContent*>(p->mTimebase.get()));
+    ++p;
+  }
+}
+
+void SMILTimeContainer::Unlink() {
+  MOZ_ASSERT(!mHoldingEntries);
+  mMilestoneEntries.Clear();
+}
+
+void SMILTimeContainer::UpdateCurrentTime() {
+  SMILTime now = IsPaused() ? mPauseStart : GetParentTime();
+  MOZ_ASSERT(now >= mParentOffset,
+             "Container has negative time with respect to parent");
+  const auto updatedCurrentTime = CheckedInt<SMILTime>(now) - mParentOffset;
+  mCurrentTime = updatedCurrentTime.isValid()
+                     ? updatedCurrentTime.value()
+                     : std::numeric_limits<SMILTime>::max();
+}
+
+void SMILTimeContainer::NotifyTimeChange() {
+  // Called when the container time is changed with respect to the document
+  // time. When this happens time dependencies in other time containers need to
+  // re-resolve their times because begin and end times are stored in container
+  // time.
+  //
+  // To get the list of timed elements with dependencies we simply re-use the
+  // milestone elements. This is because any timed element with dependents and
+  // with significant transitions yet to fire should have their next milestone
+  // registered. Other timed elements don't matter.
+
+  // Copy the timed elements to a separate array before calling
+  // HandleContainerTimeChange on each of them in case doing so mutates
+  // mMilestoneEntries.
+  nsTArray<RefPtr<mozilla::dom::SVGAnimationElement>> elems;
+
+  {
+#ifdef DEBUG
+    AutoRestore<bool> saveHolding(mHoldingEntries);
+    mHoldingEntries = true;
+#endif
+    for (const MilestoneEntry* p = mMilestoneEntries.Elements();
+         p < mMilestoneEntries.Elements() + mMilestoneEntries.Length(); ++p) {
+      elems.AppendElement(p->mTimebase.get());
+    }
+  }
+
+  for (auto& elem : elems) {
+    elem->TimedElement().HandleContainerTimeChange();
+  }
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILTimeContainer.h b/dom/smil/SMILTimeContainer.h
new file mode 100644
index 0000000000..62ea7ad2c4
--- /dev/null
+++ b/dom/smil/SMILTimeContainer.h
@@ -0,0 +1,299 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILTIMECONTAINER_H_
+#define DOM_SMIL_SMILTIMECONTAINER_H_
+
+#include "mozilla/dom/SVGAnimationElement.h"
+#include "mozilla/SMILMilestone.h"
+#include "mozilla/SMILTypes.h"
+#include "nscore.h"
+#include "nsTPriorityQueue.h"
+
+namespace mozilla {
+
+class SMILTimeValue;
+
+//----------------------------------------------------------------------
+// SMILTimeContainer
+//
+// Common base class for a time base that can be paused, resumed, and sampled.
+//
+class SMILTimeContainer {
+ public:
+  SMILTimeContainer();
+  virtual ~SMILTimeContainer();
+
+  /*
+   * Pause request types.
+   */
+  enum {
+    PAUSE_BEGIN = 1,     // Paused because timeline has yet to begin.
+    PAUSE_SCRIPT = 2,    // Paused by script.
+    PAUSE_PAGEHIDE = 4,  // Paused because our doc is hidden.
+    PAUSE_USERPREF = 8,  // Paused because animations are disabled in prefs.
+    PAUSE_IMAGE = 16     // Paused becuase we're in an image that's suspended.
+  };
+
+  /*
+   * Cause the time container to record its begin time.
+   */
+  void Begin();
+
+  /*
+   * Pause this time container
+   *
+   * @param aType The source of the pause request. Successive calls to Pause
+   * with the same aType will be ignored. The container will remain paused until
+   * each call to Pause of a given aType has been matched by at least one call
+   * to Resume with the same aType.
+   */
+  virtual void Pause(uint32_t aType);
+
+  /*
+   * Resume this time container
+   *
+   * param @aType The source of the resume request. Clears the pause flag for
+   * this particular type of pause request. When all pause flags have been
+   * cleared the time container will be resumed.
+   */
+  virtual void Resume(uint32_t aType);
+
+  /**
+   * Returns true if this time container is paused by the specified type.
+   * Note that the time container may also be paused by other types; this method
+   * does not test if aType is the exclusive pause source.
+   *
+   * @param @aType The pause source to test for.
+   * @return true if this container is paused by aType.
+   */
+  bool IsPausedByType(uint32_t aType) const { return mPauseState & aType; }
+
+  /**
+   * Returns true if this time container is paused.
+   * Generally you should test for a specific type of pausing using
+   * IsPausedByType.
+   *
+   * @return true if this container is paused, false otherwise.
+   */
+  bool IsPaused() const { return mPauseState != 0; }
+
+  /*
+   * Return the time elapsed since this time container's begin time (expressed
+   * in parent time) minus any accumulated offset from pausing.
+   */
+  SMILTime GetCurrentTimeAsSMILTime() const;
+
+  /*
+   * Seek the document timeline to the specified time.
+   *
+   * @param aSeekTo The time to seek to, expressed in this time container's time
+   * base (i.e. the same units as GetCurrentTime).
+   */
+  void SetCurrentTime(SMILTime aSeekTo);
+
+  /*
+   * Return the current time for the parent time container if any.
+   */
+  virtual SMILTime GetParentTime() const;
+
+  /*
+   * Convert container time to parent time.
+   *
+   * @param   aContainerTime The container time to convert.
+   * @return  The equivalent parent time or indefinite if the container is
+   *          paused and the time is in the future.
+   */
+  SMILTimeValue ContainerToParentTime(SMILTime aContainerTime) const;
+
+  /*
+   * Convert from parent time to container time.
+   *
+   * @param   aParentTime The parent time to convert.
+   * @return  The equivalent container time or indefinite if the container is
+   *          paused and aParentTime is after the time when the pause began.
+   */
+  SMILTimeValue ParentToContainerTime(SMILTime aParentTime) const;
+
+  /*
+   * If the container is paused, causes the pause time to be updated to the
+   * current parent time. This should be called before updating
+   * cross-container dependencies that will call ContainerToParentTime in order
+   * to provide more intuitive results.
+   */
+  void SyncPauseTime();
+
+  /*
+   * Updates the current time of this time container and calls DoSample to
+   * perform any sample-operations.
+   */
+  void Sample();
+
+  /*
+   * Return if this time container should be sampled or can be skipped.
+   *
+   * This is most useful as an optimisation for skipping time containers that
+   * don't require a sample.
+   */
+  bool NeedsSample() const { return !mPauseState || mNeedsPauseSample; }
+
+  /*
+   * Indicates if the elements of this time container need to be rewound.
+   * This occurs during a backwards seek.
+   */
+  bool NeedsRewind() const { return mNeedsRewind; }
+  void ClearNeedsRewind() { mNeedsRewind = false; }
+
+  /*
+   * Indicates the time container is currently processing a SetCurrentTime
+   * request and appropriate seek behaviour should be applied by child elements
+   * (e.g. not firing time events).
+   */
+  bool IsSeeking() const { return mIsSeeking; }
+  void MarkSeekFinished() { mIsSeeking = false; }
+
+  /*
+   * Sets the parent time container.
+   *
+   * The callee still retains ownership of the time container.
+   */
+  nsresult SetParent(SMILTimeContainer* aParent);
+
+  /*
+   * Registers an element for a sample at the given time.
+   *
+   * @param   aMilestone  The milestone to register in container time.
+   * @param   aElement    The timebase element that needs a sample at
+   *                      aMilestone.
+   */
+  void AddMilestone(const SMILMilestone& aMilestone,
+                    mozilla::dom::SVGAnimationElement& aElement);
+
+  /*
+   * Resets the list of milestones.
+   */
+  void ClearMilestones();
+
+  /*
+   * Returns the next significant transition from amongst the registered
+   * milestones.
+   *
+   * @param[out] aNextMilestone The next milestone with time in parent time.
+   *
+   * @return true if there exists another milestone, false otherwise in
+   * which case aNextMilestone will be unmodified.
+   */
+  bool GetNextMilestoneInParentTime(SMILMilestone& aNextMilestone) const;
+
+  using AnimElemArray = nsTArray<RefPtr<dom::SVGAnimationElement>>;
+
+  /*
+   * Removes and returns the timebase elements from the start of the list of
+   * timebase elements that match the given time.
+   *
+   * @param      aMilestone  The milestone time to match in parent time. This
+   *                         must be <= GetNextMilestoneInParentTime.
+   * @param[out] aMatchedElements The array to which matching elements will be
+   *                              appended.
+   * @return true if one or more elements match, false otherwise.
+   */
+  bool PopMilestoneElementsAtMilestone(const SMILMilestone& aMilestone,
+                                       AnimElemArray& aMatchedElements);
+
+  // Cycle-collection support
+  void Traverse(nsCycleCollectionTraversalCallback* aCallback);
+  void Unlink();
+
+ protected:
+  /*
+   * Per-sample operations to be performed whenever Sample() is called and
+   * NeedsSample() is true. Called after updating mCurrentTime;
+   */
+  virtual void DoSample() {}
+
+  /*
+   * Adding and removing child containers is not implemented in the base class
+   * because not all subclasses need this.
+   */
+
+  /*
+   * Adds a child time container.
+   */
+  virtual nsresult AddChild(SMILTimeContainer& aChild) {
+    return NS_ERROR_FAILURE;
+  }
+
+  /*
+   * Removes a child time container.
+   */
+  virtual void RemoveChild(SMILTimeContainer& aChild) {}
+
+  /*
+   * Implementation helper to update the current time.
+   */
+  void UpdateCurrentTime();
+
+  /*
+   * Implementation helper to notify timed elements with dependencies that the
+   * container time has changed with respect to the document time.
+   */
+  void NotifyTimeChange();
+
+  // The parent time container, if any
+  SMILTimeContainer* mParent;
+
+  // The current time established at the last call to Sample()
+  SMILTime mCurrentTime;
+
+  // The number of milliseconds for which the container has been paused
+  // (excluding the current pause interval if the container is currently
+  // paused).
+  //
+  //  Current time = parent time - mParentOffset
+  //
+  SMILTime mParentOffset;
+
+  // The timestamp in parent time when the container was paused
+  SMILTime mPauseStart;
+
+  // Whether or not a pause sample is required
+  bool mNeedsPauseSample;
+
+  bool mNeedsRewind;  // Backwards seek performed
+  bool mIsSeeking;    // Currently in the middle of a seek operation
+
+#ifdef DEBUG
+  bool mHoldingEntries;  // True if there's a raw pointer to mMilestoneEntries
+                         // on the stack.
+#endif
+
+  // A bitfield of the pause state for all pause requests
+  uint32_t mPauseState;
+
+  struct MilestoneEntry {
+    MilestoneEntry(const SMILMilestone& aMilestone,
+                   mozilla::dom::SVGAnimationElement& aElement)
+        : mMilestone(aMilestone), mTimebase(&aElement) {}
+
+    bool operator<(const MilestoneEntry& aOther) const {
+      return mMilestone < aOther.mMilestone;
+    }
+
+    SMILMilestone mMilestone;  // In container time.
+    RefPtr<mozilla::dom::SVGAnimationElement> mTimebase;
+  };
+
+  // Queue of elements with registered milestones. Used to update the model with
+  // significant transitions that occur between two samples. Since timed element
+  // re-register their milestones when they're sampled this is reset once we've
+  // taken care of the milestones before the current sample time but before we
+  // actually do the full sample.
+  nsTPriorityQueue<MilestoneEntry> mMilestoneEntries;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILTIMECONTAINER_H_
diff --git a/dom/smil/SMILTimeValue.cpp b/dom/smil/SMILTimeValue.cpp
new file mode 100644
index 0000000000..67676a329f
--- /dev/null
+++ b/dom/smil/SMILTimeValue.cpp
@@ -0,0 +1,52 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILTimeValue.h"
+#include "nsMathUtils.h"
+
+namespace mozilla {
+
+const SMILTime SMILTimeValue::kUnresolvedMillis =
+    std::numeric_limits<SMILTime>::max();
+
+//----------------------------------------------------------------------
+// SMILTimeValue methods:
+
+static inline int8_t Cmp(int64_t aA, int64_t aB) {
+  return aA == aB ? 0 : (aA > aB ? 1 : -1);
+}
+
+int8_t SMILTimeValue::CompareTo(const SMILTimeValue& aOther) const {
+  int8_t result;
+
+  if (mState == STATE_DEFINITE) {
+    result = (aOther.mState == STATE_DEFINITE)
+                 ? Cmp(mMilliseconds, aOther.mMilliseconds)
+                 : -1;
+  } else if (mState == STATE_INDEFINITE) {
+    if (aOther.mState == STATE_DEFINITE)
+      result = 1;
+    else if (aOther.mState == STATE_INDEFINITE)
+      result = 0;
+    else
+      result = -1;
+  } else {
+    result = (aOther.mState != STATE_UNRESOLVED) ? 1 : 0;
+  }
+
+  return result;
+}
+
+void SMILTimeValue::SetMillis(double aMillis, Rounding aRounding) {
+  mState = STATE_DEFINITE;
+  mMilliseconds = NS_round(aMillis);
+  if (aRounding == Rounding::EnsureNonZero && !mMilliseconds && aMillis) {
+    // Ensure we don't round small values to zero.
+    mMilliseconds = std::copysign(1.0, aMillis);
+  }
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILTimeValue.h b/dom/smil/SMILTimeValue.h
new file mode 100644
index 0000000000..19fd67b536
--- /dev/null
+++ b/dom/smil/SMILTimeValue.h
@@ -0,0 +1,145 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILTIMEVALUE_H_
+#define DOM_SMIL_SMILTIMEVALUE_H_
+
+#include "mozilla/SMILTypes.h"
+#include "nsDebug.h"
+
+namespace mozilla {
+
+/*----------------------------------------------------------------------
+ * SMILTimeValue class
+ *
+ * A tri-state time value.
+ *
+ * First a quick overview of the SMIL time data types:
+ *
+ * SMILTime          -- a timestamp in milliseconds.
+ * SMILTimeValue     -- (this class) a timestamp that can take the additional
+ *                      states 'indefinite' and 'unresolved'
+ * SMILInstanceTime  -- an SMILTimeValue used for constructing intervals. It
+ *                      contains additional fields to govern reset behavior
+ *                      and track timing dependencies (e.g. syncbase timing).
+ * SMILInterval      -- a pair of SMILInstanceTimes that defines a begin and
+ *                      an end time for animation.
+ * SMILTimeValueSpec -- a component of a begin or end attribute, such as the
+ *                      '5s' or 'a.end+2m' in begin="5s; a.end+2m". Acts as
+ *                      a broker between an SMILTimedElement and its
+ *                      SMILInstanceTimes by generating new instance times
+ *                      and handling changes to existing times.
+ *
+ * Objects of this class may be in one of three states:
+ *
+ * 1) The time is resolved and has a definite millisecond value
+ * 2) The time is resolved and indefinite
+ * 3) The time is unresolved
+ *
+ * In summary:
+ *
+ * State      | GetMillis     | IsDefinite | IsIndefinite | IsResolved
+ * -----------+---------------+------------+--------------+------------
+ * Definite   | SMILTimeValue | true       | false        | true
+ * -----------+---------------+------------+--------------+------------
+ * Indefinite | --            | false      | true         | true
+ * -----------+---------------+------------+--------------+------------
+ * Unresolved | --            | false      | false        | false
+ *
+ */
+
+class SMILTimeValue {
+ public:
+  // Creates an unresolved time value
+  SMILTimeValue()
+      : mMilliseconds(kUnresolvedMillis), mState(STATE_UNRESOLVED) {}
+
+  // Creates a resolved time value
+  explicit SMILTimeValue(SMILTime aMillis)
+      : mMilliseconds(aMillis), mState(STATE_DEFINITE) {}
+
+  // Named constructor to create an indefinite time value
+  static SMILTimeValue Indefinite() {
+    SMILTimeValue value;
+    value.SetIndefinite();
+    return value;
+  }
+
+  static SMILTimeValue Zero() { return SMILTimeValue(SMILTime(0L)); }
+
+  bool IsIndefinite() const { return mState == STATE_INDEFINITE; }
+  void SetIndefinite() {
+    mState = STATE_INDEFINITE;
+    mMilliseconds = kUnresolvedMillis;
+  }
+
+  bool IsResolved() const { return mState != STATE_UNRESOLVED; }
+  void SetUnresolved() {
+    mState = STATE_UNRESOLVED;
+    mMilliseconds = kUnresolvedMillis;
+  }
+
+  bool IsDefinite() const { return mState == STATE_DEFINITE; }
+  SMILTime GetMillis() const {
+    MOZ_ASSERT(mState == STATE_DEFINITE,
+               "GetMillis() called for unresolved or indefinite time");
+
+    return mState == STATE_DEFINITE ? mMilliseconds : kUnresolvedMillis;
+  }
+
+  bool IsZero() const {
+    return mState == STATE_DEFINITE ? mMilliseconds == 0 : false;
+  }
+
+  void SetMillis(SMILTime aMillis) {
+    mState = STATE_DEFINITE;
+    mMilliseconds = aMillis;
+  }
+
+  /*
+   * EnsureNonZero ensures values such as 0.0001s are not represented as 0
+   * for values where 0 is invalid.
+   */
+  enum class Rounding : uint8_t { EnsureNonZero, Nearest };
+
+  void SetMillis(double aMillis, Rounding aRounding);
+
+  int8_t CompareTo(const SMILTimeValue& aOther) const;
+
+  bool operator==(const SMILTimeValue& aOther) const {
+    return CompareTo(aOther) == 0;
+  }
+
+  bool operator!=(const SMILTimeValue& aOther) const {
+    return CompareTo(aOther) != 0;
+  }
+
+  bool operator<(const SMILTimeValue& aOther) const {
+    return CompareTo(aOther) < 0;
+  }
+
+  bool operator>(const SMILTimeValue& aOther) const {
+    return CompareTo(aOther) > 0;
+  }
+
+  bool operator<=(const SMILTimeValue& aOther) const {
+    return CompareTo(aOther) <= 0;
+  }
+
+  bool operator>=(const SMILTimeValue& aOther) const {
+    return CompareTo(aOther) >= 0;
+  }
+
+ private:
+  static const SMILTime kUnresolvedMillis;
+
+  SMILTime mMilliseconds;
+  enum { STATE_DEFINITE, STATE_INDEFINITE, STATE_UNRESOLVED } mState;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILTIMEVALUE_H_
diff --git a/dom/smil/SMILTimeValueSpec.cpp b/dom/smil/SMILTimeValueSpec.cpp
new file mode 100644
index 0000000000..177c813bbc
--- /dev/null
+++ b/dom/smil/SMILTimeValueSpec.cpp
@@ -0,0 +1,370 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/EventListenerManager.h"
+#include "mozilla/SMILInstanceTime.h"
+#include "mozilla/SMILInterval.h"
+#include "mozilla/SMILParserUtils.h"
+#include "mozilla/SMILTimeContainer.h"
+#include "mozilla/SMILTimedElement.h"
+#include "mozilla/SMILTimeValueSpec.h"
+#include "mozilla/SMILTimeValue.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/Event.h"
+#include "mozilla/dom/SVGAnimationElement.h"
+#include "mozilla/dom/TimeEvent.h"
+#include "nsString.h"
+#include <limits>
+
+using namespace mozilla::dom;
+
+namespace mozilla {
+
+//----------------------------------------------------------------------
+// Nested class: EventListener
+
+NS_IMPL_ISUPPORTS(SMILTimeValueSpec::EventListener, nsIDOMEventListener)
+
+NS_IMETHODIMP
+SMILTimeValueSpec::EventListener::HandleEvent(Event* aEvent) {
+  if (mSpec) {
+    mSpec->HandleEvent(aEvent);
+  }
+  return NS_OK;
+}
+
+//----------------------------------------------------------------------
+// Implementation
+
+SMILTimeValueSpec::SMILTimeValueSpec(SMILTimedElement& aOwner, bool aIsBegin)
+    : mOwner(&aOwner), mIsBegin(aIsBegin), mReferencedElement(this) {}
+
+SMILTimeValueSpec::~SMILTimeValueSpec() {
+  UnregisterFromReferencedElement(mReferencedElement.get());
+  if (mEventListener) {
+    mEventListener->Disconnect();
+    mEventListener = nullptr;
+  }
+}
+
+nsresult SMILTimeValueSpec::SetSpec(const nsAString& aStringSpec,
+                                    Element& aContextElement) {
+  SMILTimeValueSpecParams params;
+
+  if (!SMILParserUtils::ParseTimeValueSpecParams(aStringSpec, params))
+    return NS_ERROR_FAILURE;
+
+  mParams = params;
+
+  // According to SMIL 3.0:
+  //   The special value "indefinite" does not yield an instance time in the
+  //   begin list. It will, however yield a single instance with the value
+  //   "indefinite" in an end list. This value is not removed by a reset.
+  if (mParams.mType == SMILTimeValueSpecParams::OFFSET ||
+      (!mIsBegin && mParams.mType == SMILTimeValueSpecParams::INDEFINITE)) {
+    mOwner->AddInstanceTime(new SMILInstanceTime(mParams.mOffset), mIsBegin);
+  }
+
+  // Fill in the event symbol to simplify handling later
+  if (mParams.mType == SMILTimeValueSpecParams::REPEAT) {
+    mParams.mEventSymbol = nsGkAtoms::repeatEvent;
+  }
+
+  ResolveReferences(aContextElement);
+
+  return NS_OK;
+}
+
+void SMILTimeValueSpec::ResolveReferences(Element& aContextElement) {
+  if (mParams.mType != SMILTimeValueSpecParams::SYNCBASE && !IsEventBased()) {
+    return;
+  }
+
+  // If we're not bound to the document yet, don't worry, we'll get called again
+  // when that happens
+  if (!aContextElement.IsInComposedDoc()) return;
+
+  // Hold ref to the old element so that it isn't destroyed in between resetting
+  // the referenced element and using the pointer to update the referenced
+  // element.
+  RefPtr<Element> oldReferencedElement = mReferencedElement.get();
+
+  if (mParams.mDependentElemID) {
+    mReferencedElement.ResetWithID(aContextElement, mParams.mDependentElemID);
+  } else if (mParams.mType == SMILTimeValueSpecParams::EVENT) {
+    Element* target = mOwner->GetTargetElement();
+    mReferencedElement.ResetWithElement(target);
+  } else {
+    MOZ_ASSERT(false, "Syncbase or repeat spec without ID");
+  }
+  UpdateReferencedElement(oldReferencedElement, mReferencedElement.get());
+}
+
+bool SMILTimeValueSpec::IsEventBased() const {
+  return mParams.mType == SMILTimeValueSpecParams::EVENT ||
+         mParams.mType == SMILTimeValueSpecParams::REPEAT;
+}
+
+void SMILTimeValueSpec::HandleNewInterval(
+    SMILInterval& aInterval, const SMILTimeContainer* aSrcContainer) {
+  const SMILInstanceTime& baseInstance =
+      mParams.mSyncBegin ? *aInterval.Begin() : *aInterval.End();
+  SMILTimeValue newTime =
+      ConvertBetweenTimeContainers(baseInstance.Time(), aSrcContainer);
+
+  // Apply offset
+  if (!ApplyOffset(newTime)) {
+    NS_WARNING("New time overflows SMILTime, ignoring");
+    return;
+  }
+
+  // Create the instance time and register it with the interval
+  RefPtr<SMILInstanceTime> newInstance = new SMILInstanceTime(
+      newTime, SMILInstanceTime::SOURCE_SYNCBASE, this, &aInterval);
+  mOwner->AddInstanceTime(newInstance, mIsBegin);
+}
+
+void SMILTimeValueSpec::HandleTargetElementChange(Element* aNewTarget) {
+  if (!IsEventBased() || mParams.mDependentElemID) return;
+
+  mReferencedElement.ResetWithElement(aNewTarget);
+}
+
+void SMILTimeValueSpec::HandleChangedInstanceTime(
+    const SMILInstanceTime& aBaseTime, const SMILTimeContainer* aSrcContainer,
+    SMILInstanceTime& aInstanceTimeToUpdate, bool aObjectChanged) {
+  // If the instance time is fixed (e.g. because it's being used as the begin
+  // time of an active or postactive interval) we just ignore the change.
+  if (aInstanceTimeToUpdate.IsFixedTime()) return;
+
+  SMILTimeValue updatedTime =
+      ConvertBetweenTimeContainers(aBaseTime.Time(), aSrcContainer);
+
+  // Apply offset
+  if (!ApplyOffset(updatedTime)) {
+    NS_WARNING("Updated time overflows SMILTime, ignoring");
+    return;
+  }
+
+  // The timed element that owns the instance time does the updating so it can
+  // re-sort its array of instance times more efficiently
+  if (aInstanceTimeToUpdate.Time() != updatedTime || aObjectChanged) {
+    mOwner->UpdateInstanceTime(&aInstanceTimeToUpdate, updatedTime, mIsBegin);
+  }
+}
+
+void SMILTimeValueSpec::HandleDeletedInstanceTime(
+    SMILInstanceTime& aInstanceTime) {
+  mOwner->RemoveInstanceTime(&aInstanceTime, mIsBegin);
+}
+
+bool SMILTimeValueSpec::DependsOnBegin() const { return mParams.mSyncBegin; }
+
+void SMILTimeValueSpec::Traverse(
+    nsCycleCollectionTraversalCallback* aCallback) {
+  mReferencedElement.Traverse(aCallback);
+}
+
+void SMILTimeValueSpec::Unlink() {
+  UnregisterFromReferencedElement(mReferencedElement.get());
+  mReferencedElement.Unlink();
+}
+
+//----------------------------------------------------------------------
+// Implementation helpers
+
+void SMILTimeValueSpec::UpdateReferencedElement(Element* aFrom, Element* aTo) {
+  if (aFrom == aTo) return;
+
+  UnregisterFromReferencedElement(aFrom);
+
+  switch (mParams.mType) {
+    case SMILTimeValueSpecParams::SYNCBASE: {
+      SMILTimedElement* to = GetTimedElement(aTo);
+      if (to) {
+        to->AddDependent(*this);
+      }
+    } break;
+
+    case SMILTimeValueSpecParams::EVENT:
+    case SMILTimeValueSpecParams::REPEAT:
+      RegisterEventListener(aTo);
+      break;
+
+    default:
+      // not a referencing-type
+      break;
+  }
+}
+
+void SMILTimeValueSpec::UnregisterFromReferencedElement(Element* aElement) {
+  if (!aElement) return;
+
+  if (mParams.mType == SMILTimeValueSpecParams::SYNCBASE) {
+    SMILTimedElement* timedElement = GetTimedElement(aElement);
+    if (timedElement) {
+      timedElement->RemoveDependent(*this);
+    }
+    mOwner->RemoveInstanceTimesForCreator(this, mIsBegin);
+  } else if (IsEventBased()) {
+    UnregisterEventListener(aElement);
+  }
+}
+
+SMILTimedElement* SMILTimeValueSpec::GetTimedElement(Element* aElement) {
+  auto* animationElement = SVGAnimationElement::FromNodeOrNull(aElement);
+  return animationElement ? &animationElement->TimedElement() : nullptr;
+}
+
+// Indicates whether we're allowed to register an event-listener
+// when scripting is disabled.
+bool SMILTimeValueSpec::IsEventAllowedWhenScriptingIsDisabled() {
+  // The category of (SMIL-specific) "repeat(n)" events are allowed.
+  if (mParams.mType == SMILTimeValueSpecParams::REPEAT) {
+    return true;
+  }
+
+  // A specific list of other SMIL-related events are allowed, too.
+  if (mParams.mType == SMILTimeValueSpecParams::EVENT &&
+      (mParams.mEventSymbol == nsGkAtoms::repeat ||
+       mParams.mEventSymbol == nsGkAtoms::repeatEvent ||
+       mParams.mEventSymbol == nsGkAtoms::beginEvent ||
+       mParams.mEventSymbol == nsGkAtoms::endEvent)) {
+    return true;
+  }
+
+  return false;
+}
+
+void SMILTimeValueSpec::RegisterEventListener(Element* aTarget) {
+  MOZ_ASSERT(IsEventBased(),
+             "Attempting to register event-listener for unexpected "
+             "SMILTimeValueSpec type");
+  MOZ_ASSERT(mParams.mEventSymbol,
+             "Attempting to register event-listener but there is no event "
+             "name");
+
+  if (!aTarget) return;
+
+  // When script is disabled, only allow registration for limited events.
+  if (!aTarget->GetOwnerDocument()->IsScriptEnabled() &&
+      !IsEventAllowedWhenScriptingIsDisabled()) {
+    return;
+  }
+
+  if (!mEventListener) {
+    mEventListener = new EventListener(this);
+  }
+
+  EventListenerManager* elm = aTarget->GetOrCreateListenerManager();
+  if (!elm) {
+    return;
+  }
+
+  elm->AddEventListenerByType(mEventListener,
+                              nsDependentAtomString(mParams.mEventSymbol),
+                              AllEventsAtSystemGroupBubble());
+}
+
+void SMILTimeValueSpec::UnregisterEventListener(Element* aTarget) {
+  if (!aTarget || !mEventListener) {
+    return;
+  }
+
+  EventListenerManager* elm = aTarget->GetOrCreateListenerManager();
+  if (!elm) {
+    return;
+  }
+
+  elm->RemoveEventListenerByType(mEventListener,
+                                 nsDependentAtomString(mParams.mEventSymbol),
+                                 AllEventsAtSystemGroupBubble());
+}
+
+void SMILTimeValueSpec::HandleEvent(Event* aEvent) {
+  MOZ_ASSERT(mEventListener, "Got event without an event listener");
+  MOZ_ASSERT(IsEventBased(), "Got event for non-event SMILTimeValueSpec");
+  MOZ_ASSERT(aEvent, "No event supplied");
+
+  // XXX In the long run we should get the time from the event itself which will
+  // store the time in global document time which we'll need to convert to our
+  // time container
+  SMILTimeContainer* container = mOwner->GetTimeContainer();
+  if (!container) return;
+
+  if (mParams.mType == SMILTimeValueSpecParams::REPEAT &&
+      !CheckRepeatEventDetail(aEvent)) {
+    return;
+  }
+
+  SMILTime currentTime = container->GetCurrentTimeAsSMILTime();
+  SMILTimeValue newTime(currentTime);
+  if (!ApplyOffset(newTime)) {
+    NS_WARNING("New time generated from event overflows SMILTime, ignoring");
+    return;
+  }
+
+  RefPtr<SMILInstanceTime> newInstance =
+      new SMILInstanceTime(newTime, SMILInstanceTime::SOURCE_EVENT);
+  mOwner->AddInstanceTime(newInstance, mIsBegin);
+}
+
+bool SMILTimeValueSpec::CheckRepeatEventDetail(Event* aEvent) {
+  TimeEvent* timeEvent = aEvent->AsTimeEvent();
+  if (!timeEvent) {
+    NS_WARNING("Received a repeat event that was not a DOMTimeEvent");
+    return false;
+  }
+
+  int32_t detail = timeEvent->Detail();
+  return detail > 0 && (uint32_t)detail == mParams.mRepeatIteration;
+}
+
+SMILTimeValue SMILTimeValueSpec::ConvertBetweenTimeContainers(
+    const SMILTimeValue& aSrcTime, const SMILTimeContainer* aSrcContainer) {
+  // If the source time is either indefinite or unresolved the result is going
+  // to be the same
+  if (!aSrcTime.IsDefinite()) return aSrcTime;
+
+  // Convert from source time container to our parent time container
+  const SMILTimeContainer* dstContainer = mOwner->GetTimeContainer();
+  if (dstContainer == aSrcContainer) return aSrcTime;
+
+  // If one of the elements is not attached to a time container then we can't do
+  // any meaningful conversion
+  if (!aSrcContainer || !dstContainer) return SMILTimeValue();  // unresolved
+
+  SMILTimeValue docTime =
+      aSrcContainer->ContainerToParentTime(aSrcTime.GetMillis());
+
+  if (docTime.IsIndefinite())
+    // This will happen if the source container is paused and we have a future
+    // time. Just return the indefinite time.
+    return docTime;
+
+  MOZ_ASSERT(docTime.IsDefinite(),
+             "ContainerToParentTime gave us an unresolved or indefinite time");
+
+  return dstContainer->ParentToContainerTime(docTime.GetMillis());
+}
+
+bool SMILTimeValueSpec::ApplyOffset(SMILTimeValue& aTime) const {
+  // indefinite + offset = indefinite. Likewise for unresolved times.
+  if (!aTime.IsDefinite()) {
+    return true;
+  }
+
+  double resultAsDouble =
+      (double)aTime.GetMillis() + mParams.mOffset.GetMillis();
+  if (resultAsDouble > double(std::numeric_limits<SMILTime>::max()) ||
+      resultAsDouble < double(std::numeric_limits<SMILTime>::min())) {
+    return false;
+  }
+  aTime.SetMillis(aTime.GetMillis() + mParams.mOffset.GetMillis());
+  return true;
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILTimeValueSpec.h b/dom/smil/SMILTimeValueSpec.h
new file mode 100644
index 0000000000..cb0d2dd9ab
--- /dev/null
+++ b/dom/smil/SMILTimeValueSpec.h
@@ -0,0 +1,143 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILTIMEVALUESPEC_H_
+#define DOM_SMIL_SMILTIMEVALUESPEC_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/SMILTimeValueSpecParams.h"
+#include "mozilla/dom/IDTracker.h"
+#include "nsStringFwd.h"
+#include "nsIDOMEventListener.h"
+
+// XXX Avoid including this here by moving function bodies to the cpp file
+#include "mozilla/dom/Element.h"
+
+namespace mozilla {
+
+class EventListenerManager;
+class SMILInstanceTime;
+class SMILInterval;
+class SMILTimeContainer;
+class SMILTimedElement;
+class SMILTimeValue;
+
+namespace dom {
+class Event;
+}  // namespace dom
+
+//----------------------------------------------------------------------
+// SMILTimeValueSpec class
+//
+// An individual element of a 'begin' or 'end' attribute, e.g. '5s', 'a.end'.
+// This class handles the parsing of such specifications and performs the
+// necessary event handling (for event and repeat specifications)
+// and synchronisation (for syncbase specifications).
+//
+// For an overview of how this class is related to other SMIL time classes see
+// the documentation in SMILTimeValue.h
+
+class SMILTimeValueSpec {
+ public:
+  using Element = dom::Element;
+  using Event = dom::Event;
+  using IDTracker = dom::IDTracker;
+
+  SMILTimeValueSpec(SMILTimedElement& aOwner, bool aIsBegin);
+  ~SMILTimeValueSpec();
+
+  nsresult SetSpec(const nsAString& aStringSpec, Element& aContextElement);
+  void ResolveReferences(Element& aContextElement);
+  bool IsEventBased() const;
+
+  void HandleNewInterval(SMILInterval& aInterval,
+                         const SMILTimeContainer* aSrcContainer);
+  void HandleTargetElementChange(Element* aNewTarget);
+
+  // For created SMILInstanceTime objects
+  bool DependsOnBegin() const;
+  void HandleChangedInstanceTime(const SMILInstanceTime& aBaseTime,
+                                 const SMILTimeContainer* aSrcContainer,
+                                 SMILInstanceTime& aInstanceTimeToUpdate,
+                                 bool aObjectChanged);
+  void HandleDeletedInstanceTime(SMILInstanceTime& aInstanceTime);
+
+  // Cycle-collection support
+  void Traverse(nsCycleCollectionTraversalCallback* aCallback);
+  void Unlink();
+
+ protected:
+  void UpdateReferencedElement(Element* aFrom, Element* aTo);
+  void UnregisterFromReferencedElement(Element* aElement);
+  SMILTimedElement* GetTimedElement(Element* aElement);
+  bool IsEventAllowedWhenScriptingIsDisabled();
+  void RegisterEventListener(Element* aTarget);
+  void UnregisterEventListener(Element* aTarget);
+  void HandleEvent(Event* aEvent);
+  bool CheckRepeatEventDetail(Event* aEvent);
+  SMILTimeValue ConvertBetweenTimeContainers(
+      const SMILTimeValue& aSrcTime, const SMILTimeContainer* aSrcContainer);
+  bool ApplyOffset(SMILTimeValue& aTime) const;
+
+  SMILTimedElement* mOwner;
+  bool mIsBegin;  // Indicates if *we* are a begin spec,
+                  // not to be confused with
+                  // mParams.mSyncBegin which indicates
+                  // if we're synced with the begin of
+                  // the target.
+  SMILTimeValueSpecParams mParams;
+
+  /**
+   * If our SMILTimeValueSpec exists for a 'begin' or 'end' attribute with a
+   * value that specifies a time that is relative to the animation of some
+   * other element, it will create an instance of this class to reference and
+   * track that other element.  For example, if the SMILTimeValueSpec is for
+   * end='a.end+2s', an instance of this class will be created to track the
+   * element associated with the element ID "a".  This class will notify the
+   * SMILTimeValueSpec if the element that that ID identifies changes to a
+   * different element (or none).
+   */
+  class TimeReferenceTracker final : public IDTracker {
+   public:
+    explicit TimeReferenceTracker(SMILTimeValueSpec* aOwner) : mSpec(aOwner) {}
+    void ResetWithElement(Element* aTo) {
+      RefPtr<Element> from = get();
+      Unlink();
+      ElementChanged(from, aTo);
+    }
+
+   protected:
+    void ElementChanged(Element* aFrom, Element* aTo) override {
+      IDTracker::ElementChanged(aFrom, aTo);
+      mSpec->UpdateReferencedElement(aFrom, aTo);
+    }
+    bool IsPersistent() override { return true; }
+
+   private:
+    SMILTimeValueSpec* mSpec;
+  };
+
+  TimeReferenceTracker mReferencedElement;
+
+  class EventListener final : public nsIDOMEventListener {
+    ~EventListener() {}
+
+   public:
+    explicit EventListener(SMILTimeValueSpec* aOwner) : mSpec(aOwner) {}
+    void Disconnect() { mSpec = nullptr; }
+
+    NS_DECL_ISUPPORTS
+    NS_DECL_NSIDOMEVENTLISTENER
+
+   private:
+    SMILTimeValueSpec* mSpec;
+  };
+  RefPtr<EventListener> mEventListener;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILTIMEVALUESPEC_H_
diff --git a/dom/smil/SMILTimeValueSpecParams.h b/dom/smil/SMILTimeValueSpecParams.h
new file mode 100644
index 0000000000..2487168b7f
--- /dev/null
+++ b/dom/smil/SMILTimeValueSpecParams.h
@@ -0,0 +1,58 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILTIMEVALUESPECPARAMS_H_
+#define DOM_SMIL_SMILTIMEVALUESPECPARAMS_H_
+
+#include "mozilla/SMILTimeValue.h"
+#include "nsAtom.h"
+
+namespace mozilla {
+
+//----------------------------------------------------------------------
+// SMILTimeValueSpecParams
+//
+// A simple data type for storing the result of parsing a single begin or end
+// value (e.g. the '5s' in begin="5s; indefinite; a.begin+2s").
+
+class SMILTimeValueSpecParams {
+ public:
+  SMILTimeValueSpecParams()
+      : mType(INDEFINITE), mSyncBegin(false), mRepeatIteration(0) {}
+
+  // The type of value this specification describes
+  enum { OFFSET, SYNCBASE, EVENT, REPEAT, WALLCLOCK, INDEFINITE } mType;
+
+  // A clock value that is added to:
+  // - type OFFSET: the document begin
+  // - type SYNCBASE: the timebase's begin or end time
+  // - type EVENT: the event time
+  // - type REPEAT: the repeat time
+  // It is not used for WALLCLOCK or INDEFINITE times
+  SMILTimeValue mOffset;
+
+  // The base element that this specification refers to.
+  // For SYNCBASE types, this is the timebase
+  // For EVENT and REPEAT types, this is the eventbase
+  RefPtr<nsAtom> mDependentElemID;
+
+  // The event to respond to.
+  // Only used for EVENT types.
+  RefPtr<nsAtom> mEventSymbol;
+
+  // Indicates if this specification refers to the begin or end of the dependent
+  // element.
+  // Only used for SYNCBASE types.
+  bool mSyncBegin;
+
+  // The repeat iteration to respond to.
+  // Only used for mType=REPEAT.
+  uint32_t mRepeatIteration;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILTIMEVALUESPECPARAMS_H_
diff --git a/dom/smil/SMILTimedElement.cpp b/dom/smil/SMILTimedElement.cpp
new file mode 100644
index 0000000000..4be4a8840e
--- /dev/null
+++ b/dom/smil/SMILTimedElement.cpp
@@ -0,0 +1,2166 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILTimedElement.h"
+
+#include "mozilla/AutoRestore.h"
+#include "mozilla/ContentEvents.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/EventDispatcher.h"
+#include "mozilla/SMILAnimationFunction.h"
+#include "mozilla/SMILInstanceTime.h"
+#include "mozilla/SMILParserUtils.h"
+#include "mozilla/SMILTimeContainer.h"
+#include "mozilla/SMILTimeValue.h"
+#include "mozilla/SMILTimeValueSpec.h"
+#include "mozilla/dom/DocumentInlines.h"
+#include "mozilla/dom/SVGAnimationElement.h"
+#include "nsAttrValueInlines.h"
+#include "nsGkAtoms.h"
+#include "nsReadableUtils.h"
+#include "nsMathUtils.h"
+#include "nsThreadUtils.h"
+#include "prdtoa.h"
+#include "prtime.h"
+#include "nsString.h"
+#include "nsCharSeparatedTokenizer.h"
+#include <algorithm>
+
+using namespace mozilla::dom;
+
+namespace mozilla {
+
+//----------------------------------------------------------------------
+// Helper class: InstanceTimeComparator
+
+// Upon inserting an instance time into one of our instance time lists we assign
+// it a serial number. This allows us to sort the instance times in such a way
+// that where we have several equal instance times, the ones added later will
+// sort later. This means that when we call UpdateCurrentInterval during the
+// waiting state we won't unnecessarily change the begin instance.
+//
+// The serial number also means that every instance time has an unambiguous
+// position in the array so we can use RemoveElementSorted and the like.
+bool SMILTimedElement::InstanceTimeComparator::Equals(
+    const SMILInstanceTime* aElem1, const SMILInstanceTime* aElem2) const {
+  MOZ_ASSERT(aElem1 && aElem2, "Trying to compare null instance time pointers");
+  MOZ_ASSERT(aElem1->Serial() && aElem2->Serial(),
+             "Instance times have not been assigned serial numbers");
+  MOZ_ASSERT(aElem1 == aElem2 || aElem1->Serial() != aElem2->Serial(),
+             "Serial numbers are not unique");
+
+  return aElem1->Serial() == aElem2->Serial();
+}
+
+bool SMILTimedElement::InstanceTimeComparator::LessThan(
+    const SMILInstanceTime* aElem1, const SMILInstanceTime* aElem2) const {
+  MOZ_ASSERT(aElem1 && aElem2, "Trying to compare null instance time pointers");
+  MOZ_ASSERT(aElem1->Serial() && aElem2->Serial(),
+             "Instance times have not been assigned serial numbers");
+
+  int8_t cmp = aElem1->Time().CompareTo(aElem2->Time());
+  return cmp == 0 ? aElem1->Serial() < aElem2->Serial() : cmp < 0;
+}
+
+//----------------------------------------------------------------------
+// Helper class: AsyncTimeEventRunner
+
+namespace {
+class AsyncTimeEventRunner : public Runnable {
+ protected:
+  const RefPtr<nsIContent> mTarget;
+  EventMessage mMsg;
+  int32_t mDetail;
+
+ public:
+  AsyncTimeEventRunner(nsIContent* aTarget, EventMessage aMsg, int32_t aDetail)
+      : mozilla::Runnable("AsyncTimeEventRunner"),
+        mTarget(aTarget),
+        mMsg(aMsg),
+        mDetail(aDetail) {}
+
+  // TODO: Convert this to MOZ_CAN_RUN_SCRIPT (bug 1415230, bug 1535398)
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY NS_IMETHOD Run() override {
+    InternalSMILTimeEvent event(true, mMsg);
+    event.mDetail = mDetail;
+
+    RefPtr<nsPresContext> context = nullptr;
+    Document* doc = mTarget->GetComposedDoc();
+    if (doc) {
+      context = doc->GetPresContext();
+    }
+
+    return EventDispatcher::Dispatch(mTarget, context, &event);
+  }
+};
+}  // namespace
+
+//----------------------------------------------------------------------
+// Helper class: AutoIntervalUpdateBatcher
+
+// Stack-based helper class to set the mDeferIntervalUpdates flag on an
+// SMILTimedElement and perform the UpdateCurrentInterval when the object is
+// destroyed.
+//
+// If several of these objects are allocated on the stack, the update will not
+// be performed until the last object for a given SMILTimedElement is
+// destroyed.
+class MOZ_STACK_CLASS SMILTimedElement::AutoIntervalUpdateBatcher {
+ public:
+  explicit AutoIntervalUpdateBatcher(SMILTimedElement& aTimedElement)
+      : mTimedElement(aTimedElement),
+        mDidSetFlag(!aTimedElement.mDeferIntervalUpdates) {
+    mTimedElement.mDeferIntervalUpdates = true;
+  }
+
+  ~AutoIntervalUpdateBatcher() {
+    if (!mDidSetFlag) return;
+
+    mTimedElement.mDeferIntervalUpdates = false;
+
+    if (mTimedElement.mDoDeferredUpdate) {
+      mTimedElement.mDoDeferredUpdate = false;
+      mTimedElement.UpdateCurrentInterval();
+    }
+  }
+
+ private:
+  SMILTimedElement& mTimedElement;
+  bool mDidSetFlag;
+};
+
+//----------------------------------------------------------------------
+// Helper class: AutoIntervalUpdater
+
+// Stack-based helper class to call UpdateCurrentInterval when it is destroyed
+// which helps avoid bugs where we forget to call UpdateCurrentInterval in the
+// case of early returns (e.g. due to parse errors).
+//
+// This can be safely used in conjunction with AutoIntervalUpdateBatcher; any
+// calls to UpdateCurrentInterval made by this class will simply be deferred if
+// there is an AutoIntervalUpdateBatcher on the stack.
+class MOZ_STACK_CLASS SMILTimedElement::AutoIntervalUpdater {
+ public:
+  explicit AutoIntervalUpdater(SMILTimedElement& aTimedElement)
+      : mTimedElement(aTimedElement) {}
+
+  ~AutoIntervalUpdater() { mTimedElement.UpdateCurrentInterval(); }
+
+ private:
+  SMILTimedElement& mTimedElement;
+};
+
+//----------------------------------------------------------------------
+// Templated helper functions
+
+// Selectively remove elements from an array of type
+// nsTArray<RefPtr<SMILInstanceTime> > with O(n) performance.
+template <class TestFunctor>
+void SMILTimedElement::RemoveInstanceTimes(InstanceTimeList& aArray,
+                                           TestFunctor& aTest) {
+  InstanceTimeList newArray;
+  for (uint32_t i = 0; i < aArray.Length(); ++i) {
+    SMILInstanceTime* item = aArray[i].get();
+    if (aTest(item, i)) {
+      // As per bugs 665334 and 669225 we should be careful not to remove the
+      // instance time that corresponds to the previous interval's end time.
+      //
+      // Most functors supplied here fulfil this condition by checking if the
+      // instance time is marked as "ShouldPreserve" and if so, not deleting it.
+      //
+      // However, when filtering instance times, we sometimes need to drop even
+      // instance times marked as "ShouldPreserve". In that case we take special
+      // care not to delete the end instance time of the previous interval.
+      MOZ_ASSERT(!GetPreviousInterval() || item != GetPreviousInterval()->End(),
+                 "Removing end instance time of previous interval");
+      item->Unlink();
+    } else {
+      newArray.AppendElement(item);
+    }
+  }
+  aArray = std::move(newArray);
+}
+
+//----------------------------------------------------------------------
+// Static members
+
+const nsAttrValue::EnumTable SMILTimedElement::sFillModeTable[] = {
+    {"remove", FILL_REMOVE}, {"freeze", FILL_FREEZE}, {nullptr, 0}};
+
+const nsAttrValue::EnumTable SMILTimedElement::sRestartModeTable[] = {
+    {"always", RESTART_ALWAYS},
+    {"whenNotActive", RESTART_WHENNOTACTIVE},
+    {"never", RESTART_NEVER},
+    {nullptr, 0}};
+
+const SMILMilestone SMILTimedElement::sMaxMilestone(
+    std::numeric_limits<SMILTime>::max(), false);
+
+// The thresholds at which point we start filtering intervals and instance times
+// indiscriminately.
+// See FilterIntervals and FilterInstanceTimes.
+const uint8_t SMILTimedElement::sMaxNumIntervals = 20;
+const uint8_t SMILTimedElement::sMaxNumInstanceTimes = 100;
+
+// Detect if we arrive in some sort of undetected recursive syncbase dependency
+// relationship
+const uint8_t SMILTimedElement::sMaxUpdateIntervalRecursionDepth = 20;
+
+//----------------------------------------------------------------------
+// Ctor, dtor
+
+SMILTimedElement::SMILTimedElement()
+    : mAnimationElement(nullptr),
+      mFillMode(FILL_REMOVE),
+      mRestartMode(RESTART_ALWAYS),
+      mInstanceSerialIndex(0),
+      mClient(nullptr),
+      mCurrentInterval(nullptr),
+      mCurrentRepeatIteration(0),
+      mPrevRegisteredMilestone(sMaxMilestone),
+      mElementState(STATE_STARTUP),
+      mSeekState(SEEK_NOT_SEEKING),
+      mDeferIntervalUpdates(false),
+      mDoDeferredUpdate(false),
+      mIsDisabled(false),
+      mDeleteCount(0),
+      mUpdateIntervalRecursionDepth(0) {
+  mSimpleDur.SetIndefinite();
+  mMin = SMILTimeValue::Zero();
+  mMax.SetIndefinite();
+}
+
+SMILTimedElement::~SMILTimedElement() {
+  // Unlink all instance times from dependent intervals
+  for (RefPtr<SMILInstanceTime>& instance : mBeginInstances) {
+    instance->Unlink();
+  }
+  mBeginInstances.Clear();
+  for (RefPtr<SMILInstanceTime>& instance : mEndInstances) {
+    instance->Unlink();
+  }
+  mEndInstances.Clear();
+
+  // Notify anyone listening to our intervals that they're gone
+  // (We shouldn't get any callbacks from this because all our instance times
+  // are now disassociated with any intervals)
+  ClearIntervals();
+
+  // The following assertions are important in their own right (for checking
+  // correct behavior) but also because AutoIntervalUpdateBatcher holds pointers
+  // to class so if they fail there's the possibility we might have dangling
+  // pointers.
+  MOZ_ASSERT(!mDeferIntervalUpdates,
+             "Interval updates should no longer be blocked when an "
+             "SMILTimedElement disappears");
+  MOZ_ASSERT(!mDoDeferredUpdate,
+             "There should no longer be any pending updates when an "
+             "SMILTimedElement disappears");
+}
+
+void SMILTimedElement::SetAnimationElement(SVGAnimationElement* aElement) {
+  MOZ_ASSERT(aElement, "NULL owner element");
+  MOZ_ASSERT(!mAnimationElement, "Re-setting owner");
+  mAnimationElement = aElement;
+}
+
+SMILTimeContainer* SMILTimedElement::GetTimeContainer() {
+  return mAnimationElement ? mAnimationElement->GetTimeContainer() : nullptr;
+}
+
+dom::Element* SMILTimedElement::GetTargetElement() {
+  return mAnimationElement ? mAnimationElement->GetTargetElementContent()
+                           : nullptr;
+}
+
+//----------------------------------------------------------------------
+// ElementTimeControl methods
+//
+// The definition of the ElementTimeControl interface differs between SMIL
+// Animation and SVG 1.1. In SMIL Animation all methods have a void return
+// type and the new instance time is simply added to the list and restart
+// semantics are applied as with any other instance time. In the SVG definition
+// the methods return a bool depending on the restart mode.
+//
+// This inconsistency has now been addressed by an erratum in SVG 1.1:
+//
+// http://www.w3.org/2003/01/REC-SVG11-20030114-errata#elementtimecontrol-interface
+//
+// which favours the definition in SMIL, i.e. instance times are just added
+// without first checking the restart mode.
+
+nsresult SMILTimedElement::BeginElementAt(double aOffsetSeconds) {
+  SMILTimeContainer* container = GetTimeContainer();
+  if (!container) return NS_ERROR_FAILURE;
+
+  SMILTime currentTime = container->GetCurrentTimeAsSMILTime();
+  return AddInstanceTimeFromCurrentTime(currentTime, aOffsetSeconds, true);
+}
+
+nsresult SMILTimedElement::EndElementAt(double aOffsetSeconds) {
+  SMILTimeContainer* container = GetTimeContainer();
+  if (!container) return NS_ERROR_FAILURE;
+
+  SMILTime currentTime = container->GetCurrentTimeAsSMILTime();
+  return AddInstanceTimeFromCurrentTime(currentTime, aOffsetSeconds, false);
+}
+
+//----------------------------------------------------------------------
+// SVGAnimationElement methods
+
+SMILTimeValue SMILTimedElement::GetStartTime() const {
+  return mElementState == STATE_WAITING || mElementState == STATE_ACTIVE
+             ? mCurrentInterval->Begin()->Time()
+             : SMILTimeValue();
+}
+
+//----------------------------------------------------------------------
+// Hyperlinking support
+
+SMILTimeValue SMILTimedElement::GetHyperlinkTime() const {
+  SMILTimeValue hyperlinkTime;  // Default ctor creates unresolved time
+
+  if (mElementState == STATE_ACTIVE) {
+    hyperlinkTime = mCurrentInterval->Begin()->Time();
+  } else if (!mBeginInstances.IsEmpty()) {
+    hyperlinkTime = mBeginInstances[0]->Time();
+  }
+
+  return hyperlinkTime;
+}
+
+//----------------------------------------------------------------------
+// SMILTimedElement
+
+void SMILTimedElement::AddInstanceTime(SMILInstanceTime* aInstanceTime,
+                                       bool aIsBegin) {
+  MOZ_ASSERT(aInstanceTime, "Attempting to add null instance time");
+
+  // Event-sensitivity: If an element is not active (but the parent time
+  // container is), then events are only handled for begin specifications.
+  if (mElementState != STATE_ACTIVE && !aIsBegin &&
+      aInstanceTime->IsDynamic()) {
+    // No need to call Unlink here--dynamic instance times shouldn't be linked
+    // to anything that's going to miss them
+    MOZ_ASSERT(!aInstanceTime->GetBaseInterval(),
+               "Dynamic instance time has a base interval--we probably need "
+               "to unlink it if we're not going to use it");
+    return;
+  }
+
+  aInstanceTime->SetSerial(++mInstanceSerialIndex);
+  InstanceTimeList& instanceList = aIsBegin ? mBeginInstances : mEndInstances;
+  RefPtr<SMILInstanceTime>* inserted =
+      instanceList.InsertElementSorted(aInstanceTime, InstanceTimeComparator());
+  if (!inserted) {
+    NS_WARNING("Insufficient memory to insert instance time");
+    return;
+  }
+
+  UpdateCurrentInterval();
+}
+
+void SMILTimedElement::UpdateInstanceTime(SMILInstanceTime* aInstanceTime,
+                                          SMILTimeValue& aUpdatedTime,
+                                          bool aIsBegin) {
+  MOZ_ASSERT(aInstanceTime, "Attempting to update null instance time");
+
+  // The reason we update the time here and not in the SMILTimeValueSpec is
+  // that it means we *could* re-sort more efficiently by doing a sorted remove
+  // and insert but currently this doesn't seem to be necessary given how
+  // infrequently we get these change notices.
+  aInstanceTime->DependentUpdate(aUpdatedTime);
+  InstanceTimeList& instanceList = aIsBegin ? mBeginInstances : mEndInstances;
+  instanceList.Sort(InstanceTimeComparator());
+
+  // Generally speaking, UpdateCurrentInterval makes changes to the current
+  // interval and sends changes notices itself. However, in this case because
+  // instance times are shared between the instance time list and the intervals
+  // we are effectively changing the current interval outside
+  // UpdateCurrentInterval so we need to explicitly signal that we've made
+  // a change.
+  //
+  // This wouldn't be necessary if we cloned instance times on adding them to
+  // the current interval but this introduces other complications (particularly
+  // detecting which instance time is being used to define the begin of the
+  // current interval when doing a Reset).
+  bool changedCurrentInterval =
+      mCurrentInterval && (mCurrentInterval->Begin() == aInstanceTime ||
+                           mCurrentInterval->End() == aInstanceTime);
+
+  UpdateCurrentInterval(changedCurrentInterval);
+}
+
+void SMILTimedElement::RemoveInstanceTime(SMILInstanceTime* aInstanceTime,
+                                          bool aIsBegin) {
+  MOZ_ASSERT(aInstanceTime, "Attempting to remove null instance time");
+
+  // If the instance time should be kept (because it is or was the fixed end
+  // point of an interval) then just disassociate it from the creator.
+  if (aInstanceTime->ShouldPreserve()) {
+    aInstanceTime->Unlink();
+    return;
+  }
+
+  InstanceTimeList& instanceList = aIsBegin ? mBeginInstances : mEndInstances;
+  mozilla::DebugOnly<bool> found =
+      instanceList.RemoveElementSorted(aInstanceTime, InstanceTimeComparator());
+  MOZ_ASSERT(found, "Couldn't find instance time to delete");
+
+  UpdateCurrentInterval();
+}
+
+namespace {
+class MOZ_STACK_CLASS RemoveByCreator {
+ public:
+  explicit RemoveByCreator(const SMILTimeValueSpec* aCreator)
+      : mCreator(aCreator) {}
+
+  bool operator()(SMILInstanceTime* aInstanceTime, uint32_t /*aIndex*/) {
+    if (aInstanceTime->GetCreator() != mCreator) return false;
+
+    // If the instance time should be kept (because it is or was the fixed end
+    // point of an interval) then just disassociate it from the creator.
+    if (aInstanceTime->ShouldPreserve()) {
+      aInstanceTime->Unlink();
+      return false;
+    }
+
+    return true;
+  }
+
+ private:
+  const SMILTimeValueSpec* mCreator;
+};
+}  // namespace
+
+void SMILTimedElement::RemoveInstanceTimesForCreator(
+    const SMILTimeValueSpec* aCreator, bool aIsBegin) {
+  MOZ_ASSERT(aCreator, "Creator not set");
+
+  InstanceTimeList& instances = aIsBegin ? mBeginInstances : mEndInstances;
+  RemoveByCreator removeByCreator(aCreator);
+  RemoveInstanceTimes(instances, removeByCreator);
+
+  UpdateCurrentInterval();
+}
+
+void SMILTimedElement::SetTimeClient(SMILAnimationFunction* aClient) {
+  //
+  // No need to check for nullptr. A nullptr parameter simply means to remove
+  // the previous client which we do by setting to nullptr anyway.
+  //
+
+  mClient = aClient;
+}
+
+void SMILTimedElement::SampleAt(SMILTime aContainerTime) {
+  if (mIsDisabled) return;
+
+  // Milestones are cleared before a sample
+  mPrevRegisteredMilestone = sMaxMilestone;
+
+  DoSampleAt(aContainerTime, false);
+}
+
+void SMILTimedElement::SampleEndAt(SMILTime aContainerTime) {
+  if (mIsDisabled) return;
+
+  // Milestones are cleared before a sample
+  mPrevRegisteredMilestone = sMaxMilestone;
+
+  // If the current interval changes, we don't bother trying to remove any old
+  // milestones we'd registered. So it's possible to get a call here to end an
+  // interval at a time that no longer reflects the end of the current interval.
+  //
+  // For now we just check that we're actually in an interval but note that the
+  // initial sample we use to initialise the model is an end sample. This is
+  // because we want to resolve all the instance times before committing to an
+  // initial interval. Therefore an end sample from the startup state is also
+  // acceptable.
+  if (mElementState == STATE_ACTIVE || mElementState == STATE_STARTUP) {
+    DoSampleAt(aContainerTime, true);  // End sample
+  } else {
+    // Even if this was an unnecessary milestone sample we want to be sure that
+    // our next real milestone is registered.
+    RegisterMilestone();
+  }
+}
+
+void SMILTimedElement::DoSampleAt(SMILTime aContainerTime, bool aEndOnly) {
+  MOZ_ASSERT(mAnimationElement,
+             "Got sample before being registered with an animation element");
+  MOZ_ASSERT(GetTimeContainer(),
+             "Got sample without being registered with a time container");
+
+  // This could probably happen if we later implement externalResourcesRequired
+  // (bug 277955) and whilst waiting for those resources (and the animation to
+  // start) we transfer a node from another document fragment that has already
+  // started. In such a case we might receive milestone samples registered with
+  // the already active container.
+  if (GetTimeContainer()->IsPausedByType(SMILTimeContainer::PAUSE_BEGIN))
+    return;
+
+  // We use an end-sample to start animation since an end-sample lets us
+  // tentatively create an interval without committing to it (by transitioning
+  // to the ACTIVE state) and this is necessary because we might have
+  // dependencies on other animations that are yet to start. After these
+  // other animations start, it may be necessary to revise our initial interval.
+  //
+  // However, sometimes instead of an end-sample we can get a regular sample
+  // during STARTUP state. This can happen, for example, if we register
+  // a milestone before time t=0 and are then re-bound to the tree (which sends
+  // us back to the STARTUP state). In such a case we should just ignore the
+  // sample and wait for our real initial sample which will be an end-sample.
+  if (mElementState == STATE_STARTUP && !aEndOnly) return;
+
+  bool finishedSeek = false;
+  if (GetTimeContainer()->IsSeeking() && mSeekState == SEEK_NOT_SEEKING) {
+    mSeekState = mElementState == STATE_ACTIVE ? SEEK_FORWARD_FROM_ACTIVE
+                                               : SEEK_FORWARD_FROM_INACTIVE;
+  } else if (mSeekState != SEEK_NOT_SEEKING &&
+             !GetTimeContainer()->IsSeeking()) {
+    finishedSeek = true;
+  }
+
+  bool stateChanged;
+  SMILTimeValue sampleTime(aContainerTime);
+
+  do {
+#ifdef DEBUG
+    // Check invariant
+    if (mElementState == STATE_STARTUP || mElementState == STATE_POSTACTIVE) {
+      MOZ_ASSERT(!mCurrentInterval,
+                 "Shouldn't have current interval in startup or postactive "
+                 "states");
+    } else {
+      MOZ_ASSERT(mCurrentInterval,
+                 "Should have current interval in waiting and active states");
+    }
+#endif
+
+    stateChanged = false;
+
+    switch (mElementState) {
+      case STATE_STARTUP: {
+        SMILInterval firstInterval;
+        mElementState =
+            GetNextInterval(nullptr, nullptr, nullptr, firstInterval)
+                ? STATE_WAITING
+                : STATE_POSTACTIVE;
+        stateChanged = true;
+        if (mElementState == STATE_WAITING) {
+          mCurrentInterval = MakeUnique<SMILInterval>(firstInterval);
+          NotifyNewInterval();
+        }
+      } break;
+
+      case STATE_WAITING: {
+        if (mCurrentInterval->Begin()->Time() <= sampleTime) {
+          mElementState = STATE_ACTIVE;
+          mCurrentInterval->FixBegin();
+          if (mClient) {
+            mClient->Activate(mCurrentInterval->Begin()->Time().GetMillis());
+          }
+          if (mSeekState == SEEK_NOT_SEEKING) {
+            FireTimeEventAsync(eSMILBeginEvent, 0);
+          }
+          if (HasPlayed()) {
+            Reset();  // Apply restart behaviour
+            // The call to Reset() may mean that the end point of our current
+            // interval should be changed and so we should update the interval
+            // now. However, calling UpdateCurrentInterval could result in the
+            // interval getting deleted (perhaps through some web of syncbase
+            // dependencies) therefore we make updating the interval the last
+            // thing we do. There is no guarantee that mCurrentInterval is set
+            // after this.
+            UpdateCurrentInterval();
+          }
+          stateChanged = true;
+        }
+      } break;
+
+      case STATE_ACTIVE: {
+        // Ending early will change the interval but we don't notify dependents
+        // of the change until we have closed off the current interval (since we
+        // don't want dependencies to un-end our early end).
+        bool didApplyEarlyEnd = ApplyEarlyEnd(sampleTime);
+
+        if (mCurrentInterval->End()->Time() <= sampleTime) {
+          SMILInterval newInterval;
+          mElementState = GetNextInterval(mCurrentInterval.get(), nullptr,
+                                          nullptr, newInterval)
+                              ? STATE_WAITING
+                              : STATE_POSTACTIVE;
+          if (mClient) {
+            mClient->Inactivate(mFillMode == FILL_FREEZE);
+          }
+          mCurrentInterval->FixEnd();
+          if (mSeekState == SEEK_NOT_SEEKING) {
+            FireTimeEventAsync(eSMILEndEvent, 0);
+          }
+          mCurrentRepeatIteration = 0;
+          mOldIntervals.AppendElement(std::move(mCurrentInterval));
+          SampleFillValue();
+          if (mElementState == STATE_WAITING) {
+            mCurrentInterval = MakeUnique<SMILInterval>(newInterval);
+          }
+          // We are now in a consistent state to dispatch notifications
+          if (didApplyEarlyEnd) {
+            NotifyChangedInterval(mOldIntervals.LastElement().get(), false,
+                                  true);
+          }
+          if (mElementState == STATE_WAITING) {
+            NotifyNewInterval();
+          }
+          FilterHistory();
+          stateChanged = true;
+        } else if (mCurrentInterval->Begin()->Time() <= sampleTime) {
+          MOZ_ASSERT(!didApplyEarlyEnd, "We got an early end, but didn't end");
+          SMILTime beginTime = mCurrentInterval->Begin()->Time().GetMillis();
+          SMILTime activeTime = aContainerTime - beginTime;
+
+          // The 'min' attribute can cause the active interval to be longer than
+          // the 'repeating interval'.
+          // In that extended period we apply the fill mode.
+          if (GetRepeatDuration() <= SMILTimeValue(activeTime)) {
+            if (mClient && mClient->IsActive()) {
+              mClient->Inactivate(mFillMode == FILL_FREEZE);
+            }
+            SampleFillValue();
+          } else {
+            SampleSimpleTime(activeTime);
+
+            // We register our repeat times as milestones (except when we're
+            // seeking) so we should get a sample at exactly the time we repeat.
+            // (And even when we are seeking we want to update
+            // mCurrentRepeatIteration so we do that first before testing the
+            // seek state.)
+            uint32_t prevRepeatIteration = mCurrentRepeatIteration;
+            if (ActiveTimeToSimpleTime(activeTime, mCurrentRepeatIteration) ==
+                    0 &&
+                mCurrentRepeatIteration != prevRepeatIteration &&
+                mCurrentRepeatIteration && mSeekState == SEEK_NOT_SEEKING) {
+              FireTimeEventAsync(eSMILRepeatEvent,
+                                 static_cast<int32_t>(mCurrentRepeatIteration));
+            }
+          }
+        }
+        // Otherwise |sampleTime| is *before* the current interval. That
+        // normally doesn't happen but can happen if we get a stray milestone
+        // sample (e.g. if we registered a milestone with a time container that
+        // later got re-attached as a child of a more advanced time container).
+        // In that case we should just ignore the sample.
+      } break;
+
+      case STATE_POSTACTIVE:
+        break;
+    }
+
+    // Generally we continue driving the state machine so long as we have
+    // changed state. However, for end samples we only drive the state machine
+    // as far as the waiting or postactive state because we don't want to commit
+    // to any new interval (by transitioning to the active state) until all the
+    // end samples have finished and we then have complete information about the
+    // available instance times upon which to base our next interval.
+  } while (stateChanged && (!aEndOnly || (mElementState != STATE_WAITING &&
+                                          mElementState != STATE_POSTACTIVE)));
+
+  if (finishedSeek) {
+    DoPostSeek();
+  }
+  RegisterMilestone();
+}
+
+void SMILTimedElement::HandleContainerTimeChange() {
+  // In future we could possibly introduce a separate change notice for time
+  // container changes and only notify those dependents who live in other time
+  // containers. For now we don't bother because when we re-resolve the time in
+  // the SMILTimeValueSpec we'll check if anything has changed and if not, we
+  // won't go any further.
+  if (mElementState == STATE_WAITING || mElementState == STATE_ACTIVE) {
+    NotifyChangedInterval(mCurrentInterval.get(), false, false);
+  }
+}
+
+namespace {
+bool RemoveNonDynamic(SMILInstanceTime* aInstanceTime) {
+  // Generally dynamically-generated instance times (DOM calls, event-based
+  // times) are not associated with their creator SMILTimeValueSpec since
+  // they may outlive them.
+  MOZ_ASSERT(!aInstanceTime->IsDynamic() || !aInstanceTime->GetCreator(),
+             "Dynamic instance time should be unlinked from its creator");
+  return !aInstanceTime->IsDynamic() && !aInstanceTime->ShouldPreserve();
+}
+}  // namespace
+
+void SMILTimedElement::Rewind() {
+  MOZ_ASSERT(mAnimationElement,
+             "Got rewind request before being attached to an animation "
+             "element");
+
+  // It's possible to get a rewind request whilst we're already in the middle of
+  // a backwards seek. This can happen when we're performing tree surgery and
+  // seeking containers at the same time because we can end up requesting
+  // a local rewind on an element after binding it to a new container and then
+  // performing a rewind on that container as a whole without sampling in
+  // between.
+  //
+  // However, it should currently be impossible to get a rewind in the middle of
+  // a forwards seek since forwards seeks are detected and processed within the
+  // same (re)sample.
+  if (mSeekState == SEEK_NOT_SEEKING) {
+    mSeekState = mElementState == STATE_ACTIVE ? SEEK_BACKWARD_FROM_ACTIVE
+                                               : SEEK_BACKWARD_FROM_INACTIVE;
+  }
+  MOZ_ASSERT(mSeekState == SEEK_BACKWARD_FROM_INACTIVE ||
+                 mSeekState == SEEK_BACKWARD_FROM_ACTIVE,
+             "Rewind in the middle of a forwards seek?");
+
+  ClearTimingState(RemoveNonDynamic);
+  RebuildTimingState(RemoveNonDynamic);
+
+  MOZ_ASSERT(!mCurrentInterval, "Current interval is set at end of rewind");
+}
+
+namespace {
+bool RemoveAll(SMILInstanceTime* aInstanceTime) { return true; }
+}  // namespace
+
+bool SMILTimedElement::SetIsDisabled(bool aIsDisabled) {
+  if (mIsDisabled == aIsDisabled) return false;
+
+  if (aIsDisabled) {
+    mIsDisabled = true;
+    ClearTimingState(RemoveAll);
+  } else {
+    RebuildTimingState(RemoveAll);
+    mIsDisabled = false;
+  }
+  return true;
+}
+
+namespace {
+bool RemoveNonDOM(SMILInstanceTime* aInstanceTime) {
+  return !aInstanceTime->FromDOM() && !aInstanceTime->ShouldPreserve();
+}
+}  // namespace
+
+bool SMILTimedElement::SetAttr(nsAtom* aAttribute, const nsAString& aValue,
+                               nsAttrValue& aResult, Element& aContextElement,
+                               nsresult* aParseResult) {
+  bool foundMatch = true;
+  nsresult parseResult = NS_OK;
+
+  if (aAttribute == nsGkAtoms::begin) {
+    parseResult = SetBeginSpec(aValue, aContextElement, RemoveNonDOM);
+  } else if (aAttribute == nsGkAtoms::dur) {
+    parseResult = SetSimpleDuration(aValue);
+  } else if (aAttribute == nsGkAtoms::end) {
+    parseResult = SetEndSpec(aValue, aContextElement, RemoveNonDOM);
+  } else if (aAttribute == nsGkAtoms::fill) {
+    parseResult = SetFillMode(aValue);
+  } else if (aAttribute == nsGkAtoms::max) {
+    parseResult = SetMax(aValue);
+  } else if (aAttribute == nsGkAtoms::min) {
+    parseResult = SetMin(aValue);
+  } else if (aAttribute == nsGkAtoms::repeatCount) {
+    parseResult = SetRepeatCount(aValue);
+  } else if (aAttribute == nsGkAtoms::repeatDur) {
+    parseResult = SetRepeatDur(aValue);
+  } else if (aAttribute == nsGkAtoms::restart) {
+    parseResult = SetRestart(aValue);
+  } else {
+    foundMatch = false;
+  }
+
+  if (foundMatch) {
+    aResult.SetTo(aValue);
+    if (aParseResult) {
+      *aParseResult = parseResult;
+    }
+  }
+
+  return foundMatch;
+}
+
+bool SMILTimedElement::UnsetAttr(nsAtom* aAttribute) {
+  bool foundMatch = true;
+
+  if (aAttribute == nsGkAtoms::begin) {
+    UnsetBeginSpec(RemoveNonDOM);
+  } else if (aAttribute == nsGkAtoms::dur) {
+    UnsetSimpleDuration();
+  } else if (aAttribute == nsGkAtoms::end) {
+    UnsetEndSpec(RemoveNonDOM);
+  } else if (aAttribute == nsGkAtoms::fill) {
+    UnsetFillMode();
+  } else if (aAttribute == nsGkAtoms::max) {
+    UnsetMax();
+  } else if (aAttribute == nsGkAtoms::min) {
+    UnsetMin();
+  } else if (aAttribute == nsGkAtoms::repeatCount) {
+    UnsetRepeatCount();
+  } else if (aAttribute == nsGkAtoms::repeatDur) {
+    UnsetRepeatDur();
+  } else if (aAttribute == nsGkAtoms::restart) {
+    UnsetRestart();
+  } else {
+    foundMatch = false;
+  }
+
+  return foundMatch;
+}
+
+//----------------------------------------------------------------------
+// Setters and unsetters
+
+nsresult SMILTimedElement::SetBeginSpec(const nsAString& aBeginSpec,
+                                        Element& aContextElement,
+                                        RemovalTestFunction aRemove) {
+  return SetBeginOrEndSpec(aBeginSpec, aContextElement, true /*isBegin*/,
+                           aRemove);
+}
+
+void SMILTimedElement::UnsetBeginSpec(RemovalTestFunction aRemove) {
+  ClearSpecs(mBeginSpecs, mBeginInstances, aRemove);
+  UpdateCurrentInterval();
+}
+
+nsresult SMILTimedElement::SetEndSpec(const nsAString& aEndSpec,
+                                      Element& aContextElement,
+                                      RemovalTestFunction aRemove) {
+  return SetBeginOrEndSpec(aEndSpec, aContextElement, false /*!isBegin*/,
+                           aRemove);
+}
+
+void SMILTimedElement::UnsetEndSpec(RemovalTestFunction aRemove) {
+  ClearSpecs(mEndSpecs, mEndInstances, aRemove);
+  UpdateCurrentInterval();
+}
+
+nsresult SMILTimedElement::SetSimpleDuration(const nsAString& aDurSpec) {
+  // Update the current interval before returning
+  AutoIntervalUpdater updater(*this);
+
+  SMILTimeValue duration;
+  const nsAString& dur = SMILParserUtils::TrimWhitespace(aDurSpec);
+
+  // SVG-specific: "For SVG's animation elements, if "media" is specified, the
+  // attribute will be ignored." (SVG 1.1, section 19.2.6)
+  if (dur.EqualsLiteral("media") || dur.EqualsLiteral("indefinite")) {
+    duration.SetIndefinite();
+  } else {
+    if (!SMILParserUtils::ParseClockValue(
+            dur, SMILTimeValue::Rounding::EnsureNonZero, &duration) ||
+        duration.IsZero()) {
+      mSimpleDur.SetIndefinite();
+      return NS_ERROR_FAILURE;
+    }
+  }
+  // mSimpleDur should never be unresolved. ParseClockValue will either set
+  // duration to resolved or will return false.
+  MOZ_ASSERT(duration.IsResolved(), "Setting unresolved simple duration");
+
+  mSimpleDur = duration;
+
+  return NS_OK;
+}
+
+void SMILTimedElement::UnsetSimpleDuration() {
+  mSimpleDur.SetIndefinite();
+  UpdateCurrentInterval();
+}
+
+nsresult SMILTimedElement::SetMin(const nsAString& aMinSpec) {
+  // Update the current interval before returning
+  AutoIntervalUpdater updater(*this);
+
+  SMILTimeValue duration;
+  const nsAString& min = SMILParserUtils::TrimWhitespace(aMinSpec);
+
+  if (min.EqualsLiteral("media")) {
+    duration = SMILTimeValue::Zero();
+  } else {
+    if (!SMILParserUtils::ParseClockValue(min, SMILTimeValue::Rounding::Nearest,
+                                          &duration)) {
+      mMin = SMILTimeValue::Zero();
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  MOZ_ASSERT(duration.GetMillis() >= 0L, "Invalid duration");
+
+  mMin = duration;
+
+  return NS_OK;
+}
+
+void SMILTimedElement::UnsetMin() {
+  mMin = SMILTimeValue::Zero();
+  UpdateCurrentInterval();
+}
+
+nsresult SMILTimedElement::SetMax(const nsAString& aMaxSpec) {
+  // Update the current interval before returning
+  AutoIntervalUpdater updater(*this);
+
+  SMILTimeValue duration;
+  const nsAString& max = SMILParserUtils::TrimWhitespace(aMaxSpec);
+
+  if (max.EqualsLiteral("media") || max.EqualsLiteral("indefinite")) {
+    duration.SetIndefinite();
+  } else {
+    if (!SMILParserUtils::ParseClockValue(
+            max, SMILTimeValue::Rounding::EnsureNonZero, &duration) ||
+        duration.IsZero()) {
+      mMax.SetIndefinite();
+      return NS_ERROR_FAILURE;
+    }
+    MOZ_ASSERT(duration.GetMillis() > 0L, "Invalid duration");
+  }
+
+  mMax = duration;
+
+  return NS_OK;
+}
+
+void SMILTimedElement::UnsetMax() {
+  mMax.SetIndefinite();
+  UpdateCurrentInterval();
+}
+
+nsresult SMILTimedElement::SetRestart(const nsAString& aRestartSpec) {
+  nsAttrValue temp;
+  bool parseResult = temp.ParseEnumValue(aRestartSpec, sRestartModeTable, true);
+  mRestartMode =
+      parseResult ? SMILRestartMode(temp.GetEnumValue()) : RESTART_ALWAYS;
+  UpdateCurrentInterval();
+  return parseResult ? NS_OK : NS_ERROR_FAILURE;
+}
+
+void SMILTimedElement::UnsetRestart() {
+  mRestartMode = RESTART_ALWAYS;
+  UpdateCurrentInterval();
+}
+
+nsresult SMILTimedElement::SetRepeatCount(const nsAString& aRepeatCountSpec) {
+  // Update the current interval before returning
+  AutoIntervalUpdater updater(*this);
+
+  SMILRepeatCount newRepeatCount;
+
+  if (SMILParserUtils::ParseRepeatCount(aRepeatCountSpec, newRepeatCount)) {
+    mRepeatCount = newRepeatCount;
+    return NS_OK;
+  }
+  mRepeatCount.Unset();
+  return NS_ERROR_FAILURE;
+}
+
+void SMILTimedElement::UnsetRepeatCount() {
+  mRepeatCount.Unset();
+  UpdateCurrentInterval();
+}
+
+nsresult SMILTimedElement::SetRepeatDur(const nsAString& aRepeatDurSpec) {
+  // Update the current interval before returning
+  AutoIntervalUpdater updater(*this);
+
+  SMILTimeValue duration;
+
+  const nsAString& repeatDur = SMILParserUtils::TrimWhitespace(aRepeatDurSpec);
+
+  if (repeatDur.EqualsLiteral("indefinite")) {
+    duration.SetIndefinite();
+  } else {
+    if (!SMILParserUtils::ParseClockValue(
+            repeatDur, SMILTimeValue::Rounding::EnsureNonZero, &duration)) {
+      mRepeatDur.SetUnresolved();
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  mRepeatDur = duration;
+
+  return NS_OK;
+}
+
+void SMILTimedElement::UnsetRepeatDur() {
+  mRepeatDur.SetUnresolved();
+  UpdateCurrentInterval();
+}
+
+nsresult SMILTimedElement::SetFillMode(const nsAString& aFillModeSpec) {
+  uint16_t previousFillMode = mFillMode;
+
+  nsAttrValue temp;
+  bool parseResult = temp.ParseEnumValue(aFillModeSpec, sFillModeTable, true);
+  mFillMode = parseResult ? SMILFillMode(temp.GetEnumValue()) : FILL_REMOVE;
+
+  // Update fill mode of client
+  if (mFillMode != previousFillMode && HasClientInFillRange()) {
+    mClient->Inactivate(mFillMode == FILL_FREEZE);
+    SampleFillValue();
+  }
+
+  return parseResult ? NS_OK : NS_ERROR_FAILURE;
+}
+
+void SMILTimedElement::UnsetFillMode() {
+  uint16_t previousFillMode = mFillMode;
+  mFillMode = FILL_REMOVE;
+  if (previousFillMode == FILL_FREEZE && HasClientInFillRange()) {
+    mClient->Inactivate(false);
+  }
+}
+
+void SMILTimedElement::AddDependent(SMILTimeValueSpec& aDependent) {
+  // There's probably no harm in attempting to register a dependent
+  // SMILTimeValueSpec twice, but we're not expecting it to happen.
+  MOZ_ASSERT(!mTimeDependents.GetEntry(&aDependent),
+             "SMILTimeValueSpec is already registered as a dependency");
+  mTimeDependents.PutEntry(&aDependent);
+
+  // Add current interval. We could add historical intervals too but that would
+  // cause unpredictable results since some intervals may have been filtered.
+  // SMIL doesn't say what to do here so for simplicity and consistency we
+  // simply add the current interval if there is one.
+  //
+  // It's not necessary to call SyncPauseTime since we're dealing with
+  // historical instance times not newly added ones.
+  if (mCurrentInterval) {
+    aDependent.HandleNewInterval(*mCurrentInterval, GetTimeContainer());
+  }
+}
+
+void SMILTimedElement::RemoveDependent(SMILTimeValueSpec& aDependent) {
+  mTimeDependents.RemoveEntry(&aDependent);
+}
+
+bool SMILTimedElement::IsTimeDependent(const SMILTimedElement& aOther) const {
+  const SMILInstanceTime* thisBegin = GetEffectiveBeginInstance();
+  const SMILInstanceTime* otherBegin = aOther.GetEffectiveBeginInstance();
+
+  if (!thisBegin || !otherBegin) return false;
+
+  return thisBegin->IsDependentOn(*otherBegin);
+}
+
+void SMILTimedElement::BindToTree(Element& aContextElement) {
+  // Reset previously registered milestone since we may be registering with
+  // a different time container now.
+  mPrevRegisteredMilestone = sMaxMilestone;
+
+  // If we were already active then clear all our timing information and start
+  // afresh
+  if (mElementState != STATE_STARTUP) {
+    mSeekState = SEEK_NOT_SEEKING;
+    Rewind();
+  }
+
+  // Scope updateBatcher to last only for the ResolveReferences calls:
+  {
+    AutoIntervalUpdateBatcher updateBatcher(*this);
+
+    // Resolve references to other parts of the tree
+    for (UniquePtr<SMILTimeValueSpec>& beginSpec : mBeginSpecs) {
+      beginSpec->ResolveReferences(aContextElement);
+    }
+
+    for (UniquePtr<SMILTimeValueSpec>& endSpec : mEndSpecs) {
+      endSpec->ResolveReferences(aContextElement);
+    }
+  }
+
+  RegisterMilestone();
+}
+
+void SMILTimedElement::HandleTargetElementChange(Element* aNewTarget) {
+  AutoIntervalUpdateBatcher updateBatcher(*this);
+
+  for (UniquePtr<SMILTimeValueSpec>& beginSpec : mBeginSpecs) {
+    beginSpec->HandleTargetElementChange(aNewTarget);
+  }
+
+  for (UniquePtr<SMILTimeValueSpec>& endSpec : mEndSpecs) {
+    endSpec->HandleTargetElementChange(aNewTarget);
+  }
+}
+
+void SMILTimedElement::Traverse(nsCycleCollectionTraversalCallback* aCallback) {
+  for (UniquePtr<SMILTimeValueSpec>& beginSpec : mBeginSpecs) {
+    MOZ_ASSERT(beginSpec, "null SMILTimeValueSpec in list of begin specs");
+    beginSpec->Traverse(aCallback);
+  }
+
+  for (UniquePtr<SMILTimeValueSpec>& endSpec : mEndSpecs) {
+    MOZ_ASSERT(endSpec, "null SMILTimeValueSpec in list of end specs");
+    endSpec->Traverse(aCallback);
+  }
+}
+
+void SMILTimedElement::Unlink() {
+  AutoIntervalUpdateBatcher updateBatcher(*this);
+
+  // Remove dependencies on other elements
+  for (UniquePtr<SMILTimeValueSpec>& beginSpec : mBeginSpecs) {
+    MOZ_ASSERT(beginSpec, "null SMILTimeValueSpec in list of begin specs");
+    beginSpec->Unlink();
+  }
+
+  for (UniquePtr<SMILTimeValueSpec>& endSpec : mEndSpecs) {
+    MOZ_ASSERT(endSpec, "null SMILTimeValueSpec in list of end specs");
+    endSpec->Unlink();
+  }
+
+  ClearIntervals();
+
+  // Make sure we don't notify other elements of new intervals
+  mTimeDependents.Clear();
+}
+
+//----------------------------------------------------------------------
+// Implementation helpers
+
+nsresult SMILTimedElement::SetBeginOrEndSpec(const nsAString& aSpec,
+                                             Element& aContextElement,
+                                             bool aIsBegin,
+                                             RemovalTestFunction aRemove) {
+  TimeValueSpecList& timeSpecsList = aIsBegin ? mBeginSpecs : mEndSpecs;
+  InstanceTimeList& instances = aIsBegin ? mBeginInstances : mEndInstances;
+
+  ClearSpecs(timeSpecsList, instances, aRemove);
+
+  AutoIntervalUpdateBatcher updateBatcher(*this);
+
+  nsCharSeparatedTokenizer tokenizer(aSpec, ';');
+  if (!tokenizer.hasMoreTokens()) {  // Empty list
+    return NS_ERROR_FAILURE;
+  }
+
+  bool hadFailure = false;
+  while (tokenizer.hasMoreTokens()) {
+    auto spec = MakeUnique<SMILTimeValueSpec>(*this, aIsBegin);
+    nsresult rv = spec->SetSpec(tokenizer.nextToken(), aContextElement);
+    if (NS_SUCCEEDED(rv)) {
+      timeSpecsList.AppendElement(std::move(spec));
+    } else {
+      hadFailure = true;
+    }
+  }
+
+  // The return value from this function is only used to determine if we should
+  // print a console message or not, so we return failure if we had one or more
+  // failures but we don't need to differentiate between different types of
+  // failures or the number of failures.
+  return hadFailure ? NS_ERROR_FAILURE : NS_OK;
+}
+
+namespace {
+// Adaptor functor for RemoveInstanceTimes that allows us to use function
+// pointers instead.
+// Without this we'd have to either templatize ClearSpecs and all its callers
+// or pass bool flags around to specify which removal function to use here.
+class MOZ_STACK_CLASS RemoveByFunction {
+ public:
+  explicit RemoveByFunction(SMILTimedElement::RemovalTestFunction aFunction)
+      : mFunction(aFunction) {}
+  bool operator()(SMILInstanceTime* aInstanceTime, uint32_t /*aIndex*/) {
+    return mFunction(aInstanceTime);
+  }
+
+ private:
+  SMILTimedElement::RemovalTestFunction mFunction;
+};
+}  // namespace
+
+void SMILTimedElement::ClearSpecs(TimeValueSpecList& aSpecs,
+                                  InstanceTimeList& aInstances,
+                                  RemovalTestFunction aRemove) {
+  AutoIntervalUpdateBatcher updateBatcher(*this);
+
+  for (UniquePtr<SMILTimeValueSpec>& spec : aSpecs) {
+    spec->Unlink();
+  }
+  aSpecs.Clear();
+
+  RemoveByFunction removeByFunction(aRemove);
+  RemoveInstanceTimes(aInstances, removeByFunction);
+}
+
+void SMILTimedElement::ClearIntervals() {
+  if (mElementState != STATE_STARTUP) {
+    mElementState = STATE_POSTACTIVE;
+  }
+  mCurrentRepeatIteration = 0;
+  ResetCurrentInterval();
+
+  // Remove old intervals
+  for (int32_t i = mOldIntervals.Length() - 1; i >= 0; --i) {
+    mOldIntervals[i]->Unlink();
+  }
+  mOldIntervals.Clear();
+}
+
+bool SMILTimedElement::ApplyEarlyEnd(const SMILTimeValue& aSampleTime) {
+  // This should only be called within DoSampleAt as a helper function
+  MOZ_ASSERT(mElementState == STATE_ACTIVE,
+             "Unexpected state to try to apply an early end");
+
+  bool updated = false;
+
+  // Only apply an early end if we're not already ending.
+  if (mCurrentInterval->End()->Time() > aSampleTime) {
+    SMILInstanceTime* earlyEnd = CheckForEarlyEnd(aSampleTime);
+    if (earlyEnd) {
+      if (earlyEnd->IsDependent()) {
+        // Generate a new instance time for the early end since the
+        // existing instance time is part of some dependency chain that we
+        // don't want to participate in.
+        RefPtr<SMILInstanceTime> newEarlyEnd =
+            new SMILInstanceTime(earlyEnd->Time());
+        mCurrentInterval->SetEnd(*newEarlyEnd);
+      } else {
+        mCurrentInterval->SetEnd(*earlyEnd);
+      }
+      updated = true;
+    }
+  }
+  return updated;
+}
+
+namespace {
+class MOZ_STACK_CLASS RemoveReset {
+ public:
+  explicit RemoveReset(const SMILInstanceTime* aCurrentIntervalBegin)
+      : mCurrentIntervalBegin(aCurrentIntervalBegin) {}
+  bool operator()(SMILInstanceTime* aInstanceTime, uint32_t /*aIndex*/) {
+    // SMIL 3.0 section 5.4.3, 'Resetting element state':
+    //   Any instance times associated with past Event-values, Repeat-values,
+    //   Accesskey-values or added via DOM method calls are removed from the
+    //   dependent begin and end instance times lists. In effect, all events
+    //   and DOM methods calls in the past are cleared. This does not apply to
+    //   an instance time that defines the begin of the current interval.
+    return aInstanceTime->IsDynamic() && !aInstanceTime->ShouldPreserve() &&
+           (!mCurrentIntervalBegin || aInstanceTime != mCurrentIntervalBegin);
+  }
+
+ private:
+  const SMILInstanceTime* mCurrentIntervalBegin;
+};
+}  // namespace
+
+void SMILTimedElement::Reset() {
+  RemoveReset resetBegin(mCurrentInterval ? mCurrentInterval->Begin()
+                                          : nullptr);
+  RemoveInstanceTimes(mBeginInstances, resetBegin);
+
+  RemoveReset resetEnd(nullptr);
+  RemoveInstanceTimes(mEndInstances, resetEnd);
+}
+
+void SMILTimedElement::ClearTimingState(RemovalTestFunction aRemove) {
+  mElementState = STATE_STARTUP;
+  ClearIntervals();
+
+  UnsetBeginSpec(aRemove);
+  UnsetEndSpec(aRemove);
+
+  if (mClient) {
+    mClient->Inactivate(false);
+  }
+}
+
+void SMILTimedElement::RebuildTimingState(RemovalTestFunction aRemove) {
+  MOZ_ASSERT(mAnimationElement,
+             "Attempting to enable a timed element not attached to an "
+             "animation element");
+  MOZ_ASSERT(mElementState == STATE_STARTUP,
+             "Rebuilding timing state from non-startup state");
+
+  if (mAnimationElement->HasAttr(nsGkAtoms::begin)) {
+    nsAutoString attValue;
+    mAnimationElement->GetAttr(nsGkAtoms::begin, attValue);
+    SetBeginSpec(attValue, *mAnimationElement, aRemove);
+  }
+
+  if (mAnimationElement->HasAttr(nsGkAtoms::end)) {
+    nsAutoString attValue;
+    mAnimationElement->GetAttr(nsGkAtoms::end, attValue);
+    SetEndSpec(attValue, *mAnimationElement, aRemove);
+  }
+
+  mPrevRegisteredMilestone = sMaxMilestone;
+  RegisterMilestone();
+}
+
+void SMILTimedElement::DoPostSeek() {
+  // Finish backwards seek
+  if (mSeekState == SEEK_BACKWARD_FROM_INACTIVE ||
+      mSeekState == SEEK_BACKWARD_FROM_ACTIVE) {
+    // Previously some dynamic instance times may have been marked to be
+    // preserved because they were endpoints of an historic interval (which may
+    // or may not have been filtered). Now that we've finished a seek we should
+    // clear that flag for those instance times whose intervals are no longer
+    // historic.
+    UnpreserveInstanceTimes(mBeginInstances);
+    UnpreserveInstanceTimes(mEndInstances);
+
+    // Now that the times have been unmarked perform a reset. This might seem
+    // counter-intuitive when we're only doing a seek within an interval but
+    // SMIL seems to require this. SMIL 3.0, 'Hyperlinks and timing':
+    //   Resolved end times associated with events, Repeat-values,
+    //   Accesskey-values or added via DOM method calls are cleared when seeking
+    //   to time earlier than the resolved end time.
+    Reset();
+    UpdateCurrentInterval();
+  }
+
+  switch (mSeekState) {
+    case SEEK_FORWARD_FROM_ACTIVE:
+    case SEEK_BACKWARD_FROM_ACTIVE:
+      if (mElementState != STATE_ACTIVE) {
+        FireTimeEventAsync(eSMILEndEvent, 0);
+      }
+      break;
+
+    case SEEK_FORWARD_FROM_INACTIVE:
+    case SEEK_BACKWARD_FROM_INACTIVE:
+      if (mElementState == STATE_ACTIVE) {
+        FireTimeEventAsync(eSMILBeginEvent, 0);
+      }
+      break;
+
+    case SEEK_NOT_SEEKING:
+      /* Do nothing */
+      break;
+  }
+
+  mSeekState = SEEK_NOT_SEEKING;
+}
+
+void SMILTimedElement::UnpreserveInstanceTimes(InstanceTimeList& aList) {
+  const SMILInterval* prevInterval = GetPreviousInterval();
+  const SMILInstanceTime* cutoff = mCurrentInterval ? mCurrentInterval->Begin()
+                                   : prevInterval   ? prevInterval->Begin()
+                                                    : nullptr;
+  for (RefPtr<SMILInstanceTime>& instance : aList) {
+    if (!cutoff || cutoff->Time().CompareTo(instance->Time()) < 0) {
+      instance->UnmarkShouldPreserve();
+    }
+  }
+}
+
+void SMILTimedElement::FilterHistory() {
+  // We should filter the intervals first, since instance times still used in an
+  // interval won't be filtered.
+  FilterIntervals();
+  FilterInstanceTimes(mBeginInstances);
+  FilterInstanceTimes(mEndInstances);
+}
+
+void SMILTimedElement::FilterIntervals() {
+  // We can filter old intervals that:
+  //
+  // a) are not the previous interval; AND
+  // b) are not in the middle of a dependency chain; AND
+  // c) are not the first interval
+  //
+  // Condition (a) is necessary since the previous interval is used for applying
+  // fill effects and updating the current interval.
+  //
+  // Condition (b) is necessary since even if this interval itself is not
+  // active, it may be part of a dependency chain that includes active
+  // intervals. Such chains are used to establish priorities within the
+  // animation sandwich.
+  //
+  // Condition (c) is necessary to support hyperlinks that target animations
+  // since in some cases the defined behavior is to seek the document back to
+  // the first resolved begin time. Presumably the intention here is not
+  // actually to use the first resolved begin time, the
+  // _the_first_resolved_begin_time_that_produced_an_interval. That is,
+  // if we have begin="-5s; -3s; 1s; 3s" with a duration on 1s, we should seek
+  // to 1s. The spec doesn't say this but I'm pretty sure that is the intention.
+  // It seems negative times were simply not considered.
+  //
+  // Although the above conditions allow us to safely filter intervals for most
+  // scenarios they do not cover all cases and there will still be scenarios
+  // that generate intervals indefinitely. In such a case we simply set
+  // a maximum number of intervals and drop any intervals beyond that threshold.
+
+  uint32_t threshold = mOldIntervals.Length() > sMaxNumIntervals
+                           ? mOldIntervals.Length() - sMaxNumIntervals
+                           : 0;
+  IntervalList filteredList;
+  for (uint32_t i = 0; i < mOldIntervals.Length(); ++i) {
+    SMILInterval* interval = mOldIntervals[i].get();
+    if (i != 0 &&                         /*skip first interval*/
+        i + 1 < mOldIntervals.Length() && /*skip previous interval*/
+        (i < threshold || !interval->IsDependencyChainLink())) {
+      interval->Unlink(true /*filtered, not deleted*/);
+    } else {
+      filteredList.AppendElement(std::move(mOldIntervals[i]));
+    }
+  }
+  mOldIntervals = std::move(filteredList);
+}
+
+namespace {
+class MOZ_STACK_CLASS RemoveFiltered {
+ public:
+  explicit RemoveFiltered(SMILTimeValue aCutoff) : mCutoff(aCutoff) {}
+  bool operator()(SMILInstanceTime* aInstanceTime, uint32_t /*aIndex*/) {
+    // We can filter instance times that:
+    // a) Precede the end point of the previous interval; AND
+    // b) Are NOT syncbase times that might be updated to a time after the end
+    //    point of the previous interval; AND
+    // c) Are NOT fixed end points in any remaining interval.
+    return aInstanceTime->Time() < mCutoff && aInstanceTime->IsFixedTime() &&
+           !aInstanceTime->ShouldPreserve();
+  }
+
+ private:
+  SMILTimeValue mCutoff;
+};
+
+class MOZ_STACK_CLASS RemoveBelowThreshold {
+ public:
+  RemoveBelowThreshold(uint32_t aThreshold,
+                       nsTArray<const SMILInstanceTime*>& aTimesToKeep)
+      : mThreshold(aThreshold), mTimesToKeep(aTimesToKeep) {}
+  bool operator()(SMILInstanceTime* aInstanceTime, uint32_t aIndex) {
+    return aIndex < mThreshold && !mTimesToKeep.Contains(aInstanceTime);
+  }
+
+ private:
+  uint32_t mThreshold;
+  nsTArray<const SMILInstanceTime*>& mTimesToKeep;
+};
+}  // namespace
+
+void SMILTimedElement::FilterInstanceTimes(InstanceTimeList& aList) {
+  if (GetPreviousInterval()) {
+    RemoveFiltered removeFiltered(GetPreviousInterval()->End()->Time());
+    RemoveInstanceTimes(aList, removeFiltered);
+  }
+
+  // As with intervals it is possible to create a document that, even despite
+  // our most aggressive filtering, will generate instance times indefinitely
+  // (e.g. cyclic dependencies with TimeEvents---we can't filter such times as
+  // they're unpredictable due to the possibility of seeking the document which
+  // may prevent some events from being generated). Therefore we introduce
+  // a hard cutoff at which point we just drop the oldest instance times.
+  if (aList.Length() > sMaxNumInstanceTimes) {
+    uint32_t threshold = aList.Length() - sMaxNumInstanceTimes;
+    // There are a few instance times we should keep though, notably:
+    // - the current interval begin time,
+    // - the previous interval end time (see note in RemoveInstanceTimes)
+    // - the first interval begin time (see note in FilterIntervals)
+    nsTArray<const SMILInstanceTime*> timesToKeep;
+    if (mCurrentInterval) {
+      timesToKeep.AppendElement(mCurrentInterval->Begin());
+    }
+    const SMILInterval* prevInterval = GetPreviousInterval();
+    if (prevInterval) {
+      timesToKeep.AppendElement(prevInterval->End());
+    }
+    if (!mOldIntervals.IsEmpty()) {
+      timesToKeep.AppendElement(mOldIntervals[0]->Begin());
+    }
+    RemoveBelowThreshold removeBelowThreshold(threshold, timesToKeep);
+    RemoveInstanceTimes(aList, removeBelowThreshold);
+  }
+}
+
+//
+// This method is based on the pseudocode given in the SMILANIM spec.
+//
+// See:
+// http://www.w3.org/TR/2001/REC-smil-animation-20010904/#Timing-BeginEnd-LC-Start
+//
+bool SMILTimedElement::GetNextInterval(const SMILInterval* aPrevInterval,
+                                       const SMILInterval* aReplacedInterval,
+                                       const SMILInstanceTime* aFixedBeginTime,
+                                       SMILInterval& aResult) const {
+  MOZ_ASSERT(!aFixedBeginTime || aFixedBeginTime->Time().IsDefinite(),
+             "Unresolved or indefinite begin time given for interval start");
+  static const SMILTimeValue zeroTime(0L);
+
+  if (mRestartMode == RESTART_NEVER && aPrevInterval) return false;
+
+  // Calc starting point
+  SMILTimeValue beginAfter;
+  bool prevIntervalWasZeroDur = false;
+  if (aPrevInterval) {
+    beginAfter = aPrevInterval->End()->Time();
+    prevIntervalWasZeroDur =
+        aPrevInterval->End()->Time() == aPrevInterval->Begin()->Time();
+  } else {
+    beginAfter.SetMillis(INT64_MIN);
+  }
+
+  RefPtr<SMILInstanceTime> tempBegin;
+  RefPtr<SMILInstanceTime> tempEnd;
+
+  while (true) {
+    // Calculate begin time
+    if (aFixedBeginTime) {
+      if (aFixedBeginTime->Time() < beginAfter) {
+        return false;
+      }
+      // our ref-counting is not const-correct
+      tempBegin = const_cast<SMILInstanceTime*>(aFixedBeginTime);
+    } else if ((!mAnimationElement ||
+                !mAnimationElement->HasAttr(nsGkAtoms::begin)) &&
+               beginAfter <= zeroTime) {
+      tempBegin = new SMILInstanceTime(SMILTimeValue(0));
+    } else {
+      int32_t beginPos = 0;
+      do {
+        tempBegin =
+            GetNextGreaterOrEqual(mBeginInstances, beginAfter, beginPos);
+        if (!tempBegin || !tempBegin->Time().IsDefinite()) {
+          return false;
+        }
+        // If we're updating the current interval then skip any begin time that
+        // is dependent on the current interval's begin time. e.g.
+        //   <animate id="a" begin="b.begin; a.begin+2s"...
+        // If b's interval disappears whilst 'a' is in the waiting state the
+        // begin time at "a.begin+2s" should be skipped since 'a' never begun.
+      } while (aReplacedInterval &&
+               tempBegin->GetBaseTime() == aReplacedInterval->Begin());
+    }
+    MOZ_ASSERT(tempBegin && tempBegin->Time().IsDefinite() &&
+                   tempBegin->Time() >= beginAfter,
+               "Got a bad begin time while fetching next interval");
+
+    // Calculate end time
+    {
+      int32_t endPos = 0;
+      do {
+        tempEnd =
+            GetNextGreaterOrEqual(mEndInstances, tempBegin->Time(), endPos);
+
+        // SMIL doesn't allow for coincident zero-duration intervals, so if the
+        // previous interval was zero-duration, and tempEnd is going to give us
+        // another zero duration interval, then look for another end to use
+        // instead.
+        if (tempEnd && prevIntervalWasZeroDur &&
+            tempEnd->Time() == beginAfter) {
+          tempEnd = GetNextGreater(mEndInstances, tempBegin->Time(), endPos);
+        }
+        // As above with begin times, avoid creating self-referential loops
+        // between instance times by checking that the newly found end instance
+        // time is not already dependent on the end of the current interval.
+      } while (tempEnd && aReplacedInterval &&
+               tempEnd->GetBaseTime() == aReplacedInterval->End());
+
+      if (!tempEnd) {
+        // If all the ends are before the beginning we have a bad interval
+        // UNLESS:
+        // a) We never had any end attribute to begin with (the SMIL pseudocode
+        //    places this condition earlier in the flow but that fails to allow
+        //    for DOM calls when no "indefinite" condition is given), OR
+        // b) We never had any end instance times to begin with, OR
+        // c) We have end events which leave the interval open-ended.
+        bool openEndedIntervalOk = mEndSpecs.IsEmpty() ||
+                                   mEndInstances.IsEmpty() ||
+                                   EndHasEventConditions();
+
+        // The above conditions correspond with the SMIL pseudocode but SMIL
+        // doesn't address self-dependent instance times which we choose to
+        // ignore.
+        //
+        // Therefore we add a qualification of (b) above that even if
+        // there are end instance times but they all depend on the end of the
+        // current interval we should act as if they didn't exist and allow the
+        // open-ended interval.
+        //
+        // In the following condition we don't use |= because it doesn't provide
+        // short-circuit behavior.
+        openEndedIntervalOk =
+            openEndedIntervalOk ||
+            (aReplacedInterval &&
+             AreEndTimesDependentOn(aReplacedInterval->End()));
+
+        if (!openEndedIntervalOk) {
+          return false;  // Bad interval
+        }
+      }
+
+      SMILTimeValue intervalEnd = tempEnd ? tempEnd->Time() : SMILTimeValue();
+      SMILTimeValue activeEnd = CalcActiveEnd(tempBegin->Time(), intervalEnd);
+
+      if (!tempEnd || intervalEnd != activeEnd) {
+        tempEnd = new SMILInstanceTime(activeEnd);
+      }
+    }
+    MOZ_ASSERT(tempEnd, "Failed to get end point for next interval");
+
+    // When we choose the interval endpoints, we don't allow coincident
+    // zero-duration intervals, so if we arrive here and we have a zero-duration
+    // interval starting at the same point as a previous zero-duration interval,
+    // then it must be because we've applied constraints to the active duration.
+    // In that case, we will potentially run into an infinite loop, so we break
+    // it by searching for the next interval that starts AFTER our current
+    // zero-duration interval.
+    if (prevIntervalWasZeroDur && tempEnd->Time() == beginAfter) {
+      beginAfter.SetMillis(tempBegin->Time().GetMillis() + 1);
+      prevIntervalWasZeroDur = false;
+      continue;
+    }
+    prevIntervalWasZeroDur = tempBegin->Time() == tempEnd->Time();
+
+    // Check for valid interval
+    if (tempEnd->Time() > zeroTime ||
+        (tempBegin->Time() == zeroTime && tempEnd->Time() == zeroTime)) {
+      aResult.Set(*tempBegin, *tempEnd);
+      return true;
+    }
+
+    if (mRestartMode == RESTART_NEVER) {
+      // tempEnd <= 0 so we're going to loop which effectively means restarting
+      return false;
+    }
+
+    beginAfter = tempEnd->Time();
+  }
+  MOZ_ASSERT_UNREACHABLE("Hmm... we really shouldn't be here");
+
+  return false;
+}
+
+SMILInstanceTime* SMILTimedElement::GetNextGreater(
+    const InstanceTimeList& aList, const SMILTimeValue& aBase,
+    int32_t& aPosition) const {
+  SMILInstanceTime* result = nullptr;
+  while ((result = GetNextGreaterOrEqual(aList, aBase, aPosition)) &&
+         result->Time() == aBase) {
+  }
+  return result;
+}
+
+SMILInstanceTime* SMILTimedElement::GetNextGreaterOrEqual(
+    const InstanceTimeList& aList, const SMILTimeValue& aBase,
+    int32_t& aPosition) const {
+  SMILInstanceTime* result = nullptr;
+  int32_t count = aList.Length();
+
+  for (; aPosition < count && !result; ++aPosition) {
+    SMILInstanceTime* val = aList[aPosition].get();
+    MOZ_ASSERT(val, "NULL instance time in list");
+    if (val->Time() >= aBase) {
+      result = val;
+    }
+  }
+
+  return result;
+}
+
+/**
+ * @see SMILANIM 3.3.4
+ */
+SMILTimeValue SMILTimedElement::CalcActiveEnd(const SMILTimeValue& aBegin,
+                                              const SMILTimeValue& aEnd) const {
+  SMILTimeValue result;
+
+  MOZ_ASSERT(mSimpleDur.IsResolved(),
+             "Unresolved simple duration in CalcActiveEnd");
+  MOZ_ASSERT(aBegin.IsDefinite(),
+             "Indefinite or unresolved begin time in CalcActiveEnd");
+
+  result = GetRepeatDuration();
+
+  if (aEnd.IsDefinite()) {
+    SMILTime activeDur = aEnd.GetMillis() - aBegin.GetMillis();
+
+    if (result.IsDefinite()) {
+      result.SetMillis(std::min(result.GetMillis(), activeDur));
+    } else {
+      result.SetMillis(activeDur);
+    }
+  }
+
+  result = ApplyMinAndMax(result);
+
+  if (result.IsDefinite()) {
+    SMILTime activeEnd = result.GetMillis() + aBegin.GetMillis();
+    result.SetMillis(activeEnd);
+  }
+
+  return result;
+}
+
+SMILTimeValue SMILTimedElement::GetRepeatDuration() const {
+  SMILTimeValue multipliedDuration;
+  if (mRepeatCount.IsDefinite() && mSimpleDur.IsDefinite()) {
+    if (mRepeatCount * double(mSimpleDur.GetMillis()) <
+        double(std::numeric_limits<SMILTime>::max())) {
+      multipliedDuration.SetMillis(
+          SMILTime(mRepeatCount * mSimpleDur.GetMillis()));
+    }
+  } else {
+    multipliedDuration.SetIndefinite();
+  }
+
+  SMILTimeValue repeatDuration;
+
+  if (mRepeatDur.IsResolved()) {
+    repeatDuration = std::min(multipliedDuration, mRepeatDur);
+  } else if (mRepeatCount.IsSet()) {
+    repeatDuration = multipliedDuration;
+  } else {
+    repeatDuration = mSimpleDur;
+  }
+
+  return repeatDuration;
+}
+
+SMILTimeValue SMILTimedElement::ApplyMinAndMax(
+    const SMILTimeValue& aDuration) const {
+  if (!aDuration.IsResolved()) {
+    return aDuration;
+  }
+
+  if (mMax < mMin) {
+    return aDuration;
+  }
+
+  SMILTimeValue result;
+
+  if (aDuration > mMax) {
+    result = mMax;
+  } else if (aDuration < mMin) {
+    result = mMin;
+  } else {
+    result = aDuration;
+  }
+
+  return result;
+}
+
+SMILTime SMILTimedElement::ActiveTimeToSimpleTime(SMILTime aActiveTime,
+                                                  uint32_t& aRepeatIteration) {
+  SMILTime result;
+
+  MOZ_ASSERT(mSimpleDur.IsResolved(),
+             "Unresolved simple duration in ActiveTimeToSimpleTime");
+  MOZ_ASSERT(aActiveTime >= 0, "Expecting non-negative active time");
+  // Note that a negative aActiveTime will give us a negative value for
+  // aRepeatIteration, which is bad because aRepeatIteration is unsigned
+
+  if (mSimpleDur.IsIndefinite() || mSimpleDur.IsZero()) {
+    aRepeatIteration = 0;
+    result = aActiveTime;
+  } else {
+    result = aActiveTime % mSimpleDur.GetMillis();
+    aRepeatIteration = (uint32_t)(aActiveTime / mSimpleDur.GetMillis());
+  }
+
+  return result;
+}
+
+//
+// Although in many cases it would be possible to check for an early end and
+// adjust the current interval well in advance the SMIL Animation spec seems to
+// indicate that we should only apply an early end at the latest possible
+// moment. In particular, this paragraph from section 3.6.8:
+//
+// 'If restart  is set to "always", then the current interval will end early if
+// there is an instance time in the begin list that is before (i.e. earlier
+// than) the defined end for the current interval. Ending in this manner will
+// also send a changed time notice to all time dependents for the current
+// interval end.'
+//
+SMILInstanceTime* SMILTimedElement::CheckForEarlyEnd(
+    const SMILTimeValue& aContainerTime) const {
+  MOZ_ASSERT(mCurrentInterval,
+             "Checking for an early end but the current interval is not set");
+  if (mRestartMode != RESTART_ALWAYS) return nullptr;
+
+  int32_t position = 0;
+  SMILInstanceTime* nextBegin = GetNextGreater(
+      mBeginInstances, mCurrentInterval->Begin()->Time(), position);
+
+  if (nextBegin && nextBegin->Time() > mCurrentInterval->Begin()->Time() &&
+      nextBegin->Time() < mCurrentInterval->End()->Time() &&
+      nextBegin->Time() <= aContainerTime) {
+    return nextBegin;
+  }
+
+  return nullptr;
+}
+
+void SMILTimedElement::UpdateCurrentInterval(bool aForceChangeNotice) {
+  // Check if updates are currently blocked (batched)
+  if (mDeferIntervalUpdates) {
+    mDoDeferredUpdate = true;
+    return;
+  }
+
+  // We adopt the convention of not resolving intervals until the first
+  // sample. Otherwise, every time each attribute is set we'll re-resolve the
+  // current interval and notify all our time dependents of the change.
+  //
+  // The disadvantage of deferring resolving the interval is that DOM calls to
+  // to getStartTime will throw an INVALID_STATE_ERR exception until the
+  // document timeline begins since the start time has not yet been resolved.
+  if (mElementState == STATE_STARTUP) return;
+
+  // Although SMIL gives rules for detecting cycles in change notifications,
+  // some configurations can lead to create-delete-create-delete-etc. cycles
+  // which SMIL does not consider.
+  //
+  // In order to provide consistent behavior in such cases, we detect two
+  // deletes in a row and then refuse to create any further intervals. That is,
+  // we say the configuration is invalid.
+  if (mDeleteCount > 1) {
+    // When we update the delete count we also set the state to post active, so
+    // if we're not post active here then something other than
+    // UpdateCurrentInterval has updated the element state in between and all
+    // bets are off.
+    MOZ_ASSERT(mElementState == STATE_POSTACTIVE,
+               "Expected to be in post-active state after performing double "
+               "delete");
+    return;
+  }
+
+  // Check that we aren't stuck in infinite recursion updating some syncbase
+  // dependencies. Generally such situations should be detected in advance and
+  // the chain broken in a sensible and predictable manner, so if we're hitting
+  // this assertion we need to work out how to detect the case that's causing
+  // it. In release builds, just bail out before we overflow the stack.
+  AutoRestore<uint8_t> depthRestorer(mUpdateIntervalRecursionDepth);
+  if (++mUpdateIntervalRecursionDepth > sMaxUpdateIntervalRecursionDepth) {
+    MOZ_ASSERT(false,
+               "Update current interval recursion depth exceeded threshold");
+    return;
+  }
+
+  // If the interval is active the begin time is fixed.
+  const SMILInstanceTime* beginTime =
+      mElementState == STATE_ACTIVE ? mCurrentInterval->Begin() : nullptr;
+  SMILInterval updatedInterval;
+  if (GetNextInterval(GetPreviousInterval(), mCurrentInterval.get(), beginTime,
+                      updatedInterval)) {
+    if (mElementState == STATE_POSTACTIVE) {
+      MOZ_ASSERT(!mCurrentInterval,
+                 "In postactive state but the interval has been set");
+      mCurrentInterval = MakeUnique<SMILInterval>(updatedInterval);
+      mElementState = STATE_WAITING;
+      NotifyNewInterval();
+
+    } else {
+      bool beginChanged = false;
+      bool endChanged = false;
+
+      if (mElementState != STATE_ACTIVE &&
+          !updatedInterval.Begin()->SameTimeAndBase(
+              *mCurrentInterval->Begin())) {
+        mCurrentInterval->SetBegin(*updatedInterval.Begin());
+        beginChanged = true;
+      }
+
+      if (!updatedInterval.End()->SameTimeAndBase(*mCurrentInterval->End())) {
+        mCurrentInterval->SetEnd(*updatedInterval.End());
+        endChanged = true;
+      }
+
+      if (beginChanged || endChanged || aForceChangeNotice) {
+        NotifyChangedInterval(mCurrentInterval.get(), beginChanged, endChanged);
+      }
+    }
+
+    // There's a chance our next milestone has now changed, so update the time
+    // container
+    RegisterMilestone();
+  } else {  // GetNextInterval failed: Current interval is no longer valid
+    if (mElementState == STATE_ACTIVE) {
+      // The interval is active so we can't just delete it, instead trim it so
+      // that begin==end.
+      if (!mCurrentInterval->End()->SameTimeAndBase(
+              *mCurrentInterval->Begin())) {
+        mCurrentInterval->SetEnd(*mCurrentInterval->Begin());
+        NotifyChangedInterval(mCurrentInterval.get(), false, true);
+      }
+      // The transition to the postactive state will take place on the next
+      // sample (along with firing end events, clearing intervals etc.)
+      RegisterMilestone();
+    } else if (mElementState == STATE_WAITING) {
+      AutoRestore<uint8_t> deleteCountRestorer(mDeleteCount);
+      ++mDeleteCount;
+      mElementState = STATE_POSTACTIVE;
+      ResetCurrentInterval();
+    }
+  }
+}
+
+void SMILTimedElement::SampleSimpleTime(SMILTime aActiveTime) {
+  if (mClient) {
+    uint32_t repeatIteration;
+    SMILTime simpleTime = ActiveTimeToSimpleTime(aActiveTime, repeatIteration);
+    mClient->SampleAt(simpleTime, mSimpleDur, repeatIteration);
+  }
+}
+
+void SMILTimedElement::SampleFillValue() {
+  if (mFillMode != FILL_FREEZE || !mClient) return;
+
+  SMILTime activeTime;
+
+  if (mElementState == STATE_WAITING || mElementState == STATE_POSTACTIVE) {
+    const SMILInterval* prevInterval = GetPreviousInterval();
+    MOZ_ASSERT(prevInterval,
+               "Attempting to sample fill value but there is no previous "
+               "interval");
+    MOZ_ASSERT(prevInterval->End()->Time().IsDefinite() &&
+                   prevInterval->End()->IsFixedTime(),
+               "Attempting to sample fill value but the endpoint of the "
+               "previous interval is not resolved and fixed");
+
+    activeTime = prevInterval->End()->Time().GetMillis() -
+                 prevInterval->Begin()->Time().GetMillis();
+
+    // If the interval's repeat duration was shorter than its active duration,
+    // use the end of the repeat duration to determine the frozen animation's
+    // state.
+    SMILTimeValue repeatDuration = GetRepeatDuration();
+    if (repeatDuration.IsDefinite()) {
+      activeTime = std::min(repeatDuration.GetMillis(), activeTime);
+    }
+  } else {
+    MOZ_ASSERT(
+        mElementState == STATE_ACTIVE,
+        "Attempting to sample fill value when we're in an unexpected state "
+        "(probably STATE_STARTUP)");
+
+    // If we are being asked to sample the fill value while active we *must*
+    // have a repeat duration shorter than the active duration so use that.
+    MOZ_ASSERT(GetRepeatDuration().IsDefinite(),
+               "Attempting to sample fill value of an active animation with "
+               "an indefinite repeat duration");
+    activeTime = GetRepeatDuration().GetMillis();
+  }
+
+  uint32_t repeatIteration;
+  SMILTime simpleTime = ActiveTimeToSimpleTime(activeTime, repeatIteration);
+
+  if (simpleTime == 0L && repeatIteration) {
+    mClient->SampleLastValue(--repeatIteration);
+  } else {
+    mClient->SampleAt(simpleTime, mSimpleDur, repeatIteration);
+  }
+}
+
+nsresult SMILTimedElement::AddInstanceTimeFromCurrentTime(SMILTime aCurrentTime,
+                                                          double aOffsetSeconds,
+                                                          bool aIsBegin) {
+  double offset = NS_round(aOffsetSeconds * PR_MSEC_PER_SEC);
+
+  // Check we won't overflow the range of SMILTime
+  if (aCurrentTime + offset > double(std::numeric_limits<SMILTime>::max()))
+    return NS_ERROR_ILLEGAL_VALUE;
+
+  SMILTimeValue timeVal(aCurrentTime + int64_t(offset));
+
+  RefPtr<SMILInstanceTime> instanceTime =
+      new SMILInstanceTime(timeVal, SMILInstanceTime::SOURCE_DOM);
+
+  AddInstanceTime(instanceTime, aIsBegin);
+
+  return NS_OK;
+}
+
+void SMILTimedElement::RegisterMilestone() {
+  SMILTimeContainer* container = GetTimeContainer();
+  if (!container) return;
+  MOZ_ASSERT(mAnimationElement,
+             "Got a time container without an owning animation element");
+
+  SMILMilestone nextMilestone;
+  if (!GetNextMilestone(nextMilestone)) return;
+
+  // This method is called every time we might possibly have updated our
+  // current interval, but since SMILTimeContainer makes no attempt to filter
+  // out redundant milestones we do some rudimentary filtering here. It's not
+  // perfect, but unnecessary samples are fairly cheap.
+  if (nextMilestone >= mPrevRegisteredMilestone) return;
+
+  container->AddMilestone(nextMilestone, *mAnimationElement);
+  mPrevRegisteredMilestone = nextMilestone;
+}
+
+bool SMILTimedElement::GetNextMilestone(SMILMilestone& aNextMilestone) const {
+  // Return the next key moment in our lifetime.
+  //
+  // XXX It may be possible in future to optimise this so that we only register
+  // for milestones if:
+  // a) We have time dependents, or
+  // b) We are dependent on events or syncbase relationships, or
+  // c) There are registered listeners for our events
+  //
+  // Then for the simple case where everything uses offset values we could
+  // ignore milestones altogether.
+  //
+  // We'd need to be careful, however, that if one of those conditions became
+  // true in between samples that we registered our next milestone at that
+  // point.
+
+  switch (mElementState) {
+    case STATE_STARTUP:
+      // All elements register for an initial end sample at t=0 where we resolve
+      // our initial interval.
+      aNextMilestone.mIsEnd = true;  // Initial sample should be an end sample
+      aNextMilestone.mTime = 0;
+      return true;
+
+    case STATE_WAITING:
+      MOZ_ASSERT(mCurrentInterval,
+                 "In waiting state but the current interval has not been set");
+      aNextMilestone.mIsEnd = false;
+      aNextMilestone.mTime = mCurrentInterval->Begin()->Time().GetMillis();
+      return true;
+
+    case STATE_ACTIVE: {
+      // Work out what comes next: the interval end or the next repeat iteration
+      SMILTimeValue nextRepeat;
+      if (mSeekState == SEEK_NOT_SEEKING && mSimpleDur.IsDefinite()) {
+        SMILTime nextRepeatActiveTime =
+            (mCurrentRepeatIteration + 1) * mSimpleDur.GetMillis();
+        // Check that the repeat fits within the repeat duration
+        if (SMILTimeValue(nextRepeatActiveTime) < GetRepeatDuration()) {
+          nextRepeat.SetMillis(mCurrentInterval->Begin()->Time().GetMillis() +
+                               nextRepeatActiveTime);
+        }
+      }
+      SMILTimeValue nextMilestone =
+          std::min(mCurrentInterval->End()->Time(), nextRepeat);
+
+      // Check for an early end before that time
+      SMILInstanceTime* earlyEnd = CheckForEarlyEnd(nextMilestone);
+      if (earlyEnd) {
+        aNextMilestone.mIsEnd = true;
+        aNextMilestone.mTime = earlyEnd->Time().GetMillis();
+        return true;
+      }
+
+      // Apply the previously calculated milestone
+      if (nextMilestone.IsDefinite()) {
+        aNextMilestone.mIsEnd = nextMilestone != nextRepeat;
+        aNextMilestone.mTime = nextMilestone.GetMillis();
+        return true;
+      }
+
+      return false;
+    }
+
+    case STATE_POSTACTIVE:
+      return false;
+  }
+  MOZ_CRASH("Invalid element state");
+}
+
+void SMILTimedElement::NotifyNewInterval() {
+  MOZ_ASSERT(mCurrentInterval,
+             "Attempting to notify dependents of a new interval but the "
+             "interval is not set");
+
+  SMILTimeContainer* container = GetTimeContainer();
+  if (container) {
+    container->SyncPauseTime();
+  }
+
+  for (SMILTimeValueSpec* spec : mTimeDependents.Keys()) {
+    SMILInterval* interval = mCurrentInterval.get();
+    // It's possible that in notifying one new time dependent of a new interval
+    // that a chain reaction is triggered which results in the original
+    // interval disappearing. If that's the case we can skip sending further
+    // notifications.
+    if (!interval) {
+      break;
+    }
+    spec->HandleNewInterval(*interval, container);
+  }
+}
+
+void SMILTimedElement::NotifyChangedInterval(SMILInterval* aInterval,
+                                             bool aBeginObjectChanged,
+                                             bool aEndObjectChanged) {
+  MOZ_ASSERT(aInterval, "Null interval for change notification");
+
+  SMILTimeContainer* container = GetTimeContainer();
+  if (container) {
+    container->SyncPauseTime();
+  }
+
+  // Copy the instance times list since notifying the instance times can result
+  // in a chain reaction whereby our own interval gets deleted along with its
+  // instance times.
+  InstanceTimeList times;
+  aInterval->GetDependentTimes(times);
+
+  for (RefPtr<SMILInstanceTime>& time : times) {
+    time->HandleChangedInterval(container, aBeginObjectChanged,
+                                aEndObjectChanged);
+  }
+}
+
+void SMILTimedElement::FireTimeEventAsync(EventMessage aMsg, int32_t aDetail) {
+  if (!mAnimationElement) return;
+
+  nsCOMPtr<nsIRunnable> event =
+      new AsyncTimeEventRunner(mAnimationElement, aMsg, aDetail);
+  mAnimationElement->OwnerDoc()->Dispatch(event.forget());
+}
+
+const SMILInstanceTime* SMILTimedElement::GetEffectiveBeginInstance() const {
+  switch (mElementState) {
+    case STATE_STARTUP:
+      return nullptr;
+
+    case STATE_ACTIVE:
+      return mCurrentInterval->Begin();
+
+    case STATE_WAITING:
+    case STATE_POSTACTIVE: {
+      const SMILInterval* prevInterval = GetPreviousInterval();
+      return prevInterval ? prevInterval->Begin() : nullptr;
+    }
+  }
+  MOZ_CRASH("Invalid element state");
+}
+
+const SMILInterval* SMILTimedElement::GetPreviousInterval() const {
+  return mOldIntervals.IsEmpty() ? nullptr : mOldIntervals.LastElement().get();
+}
+
+bool SMILTimedElement::HasClientInFillRange() const {
+  // Returns true if we have a client that is in the range where it will fill
+  return mClient && ((mElementState != STATE_ACTIVE && HasPlayed()) ||
+                     (mElementState == STATE_ACTIVE && !mClient->IsActive()));
+}
+
+bool SMILTimedElement::EndHasEventConditions() const {
+  for (const UniquePtr<SMILTimeValueSpec>& endSpec : mEndSpecs) {
+    if (endSpec->IsEventBased()) return true;
+  }
+  return false;
+}
+
+bool SMILTimedElement::AreEndTimesDependentOn(
+    const SMILInstanceTime* aBase) const {
+  if (mEndInstances.IsEmpty()) return false;
+
+  for (const RefPtr<SMILInstanceTime>& endInstance : mEndInstances) {
+    if (endInstance->GetBaseTime() != aBase) {
+      return false;
+    }
+  }
+  return true;
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILTimedElement.h b/dom/smil/SMILTimedElement.h
new file mode 100644
index 0000000000..fc2792d1dc
--- /dev/null
+++ b/dom/smil/SMILTimedElement.h
@@ -0,0 +1,649 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILTIMEDELEMENT_H_
+#define DOM_SMIL_SMILTIMEDELEMENT_H_
+
+#include <utility>
+
+#include "mozilla/EventForwards.h"
+#include "mozilla/SMILInstanceTime.h"
+#include "mozilla/SMILInterval.h"
+#include "mozilla/SMILMilestone.h"
+#include "mozilla/SMILRepeatCount.h"
+#include "mozilla/SMILTimeValueSpec.h"
+#include "mozilla/SMILTypes.h"
+#include "mozilla/UniquePtr.h"
+#include "nsAttrValue.h"
+#include "nsHashKeys.h"
+#include "nsTArray.h"
+#include "nsTHashtable.h"
+
+class nsAtom;
+
+namespace mozilla {
+
+class SMILAnimationFunction;
+class SMILTimeContainer;
+class SMILTimeValue;
+
+namespace dom {
+class SVGAnimationElement;
+}  // namespace dom
+
+//----------------------------------------------------------------------
+// SMILTimedElement
+
+class SMILTimedElement {
+ public:
+  SMILTimedElement();
+  ~SMILTimedElement();
+
+  using Element = dom::Element;
+
+  /*
+   * Sets the owning animation element which this class uses to convert between
+   * container times and to register timebase elements.
+   */
+  void SetAnimationElement(mozilla::dom::SVGAnimationElement* aElement);
+
+  /*
+   * Returns the time container with which this timed element is associated or
+   * nullptr if it is not associated with a time container.
+   */
+  SMILTimeContainer* GetTimeContainer();
+
+  /*
+   * Returns the element targeted by the animation element. Needed for
+   * registering event listeners against the appropriate element.
+   */
+  Element* GetTargetElement();
+
+  /**
+   * Methods for supporting the ElementTimeControl interface.
+   */
+
+  /*
+   * Adds a new begin instance time at the current container time plus or minus
+   * the specified offset.
+   *
+   * @param aOffsetSeconds A real number specifying the number of seconds to add
+   *                       to the current container time.
+   * @return NS_OK if the operation succeeeded, or an error code otherwise.
+   */
+  nsresult BeginElementAt(double aOffsetSeconds);
+
+  /*
+   * Adds a new end instance time at the current container time plus or minus
+   * the specified offset.
+   *
+   * @param aOffsetSeconds A real number specifying the number of seconds to add
+   *                       to the current container time.
+   * @return NS_OK if the operation succeeeded, or an error code otherwise.
+   */
+  nsresult EndElementAt(double aOffsetSeconds);
+
+  /**
+   * Methods for supporting the SVGAnimationElement interface.
+   */
+
+  /**
+   * According to SVG 1.1 SE this returns
+   *
+   *   the begin time, in seconds, for this animation element's current
+   *   interval, if it exists, regardless of whether the interval has begun yet.
+   *
+   * @return the start time as defined above in milliseconds or an unresolved
+   * time if there is no current interval.
+   */
+  SMILTimeValue GetStartTime() const;
+
+  /**
+   * Returns the simple duration of this element.
+   *
+   * @return the simple duration in milliseconds or INDEFINITE.
+   */
+  SMILTimeValue GetSimpleDuration() const { return mSimpleDur; }
+
+  /**
+   * Methods for supporting hyperlinking
+   */
+
+  /**
+   * Internal SMIL methods
+   */
+
+  /**
+   * Returns the time to seek the document to when this element is targetted by
+   * a hyperlink.
+   *
+   * The behavior is defined here:
+   *   http://www.w3.org/TR/smil-animation/#HyperlinkSemantics
+   *
+   * It is very similar to GetStartTime() with the exception that when the
+   * element is not active, the begin time of the *first* interval is returned.
+   *
+   * @return the time to seek the documen to in milliseconds or an unresolved
+   * time if there is no resolved interval.
+   */
+  SMILTimeValue GetHyperlinkTime() const;
+
+  /**
+   * Adds an instance time object this element's list of instance times.
+   * These instance times are used when creating intervals.
+   *
+   * This method is typically called by an SMILTimeValueSpec.
+   *
+   * @param aInstanceTime   The time to add, expressed in container time.
+   * @param aIsBegin        true if the time to be added represents a begin
+   *                        time or false if it represents an end time.
+   */
+  void AddInstanceTime(SMILInstanceTime* aInstanceTime, bool aIsBegin);
+
+  /**
+   * Requests this element update the given instance time.
+   *
+   * This method is typically called by a child SMILTimeValueSpec.
+   *
+   * @param aInstanceTime   The instance time to update.
+   * @param aUpdatedTime    The time to update aInstanceTime with.
+   * @param aDependentTime  The instance time upon which aInstanceTime should be
+   *                        based.
+   * @param aIsBegin        true if the time to be updated represents a begin
+   *                        instance time or false if it represents an end
+   *                        instance time.
+   */
+  void UpdateInstanceTime(SMILInstanceTime* aInstanceTime,
+                          SMILTimeValue& aUpdatedTime, bool aIsBegin);
+
+  /**
+   * Removes an instance time object from this element's list of instance times.
+   *
+   * This method is typically called by a child SMILTimeValueSpec.
+   *
+   * @param aInstanceTime   The instance time to remove.
+   * @param aIsBegin        true if the time to be removed represents a begin
+   *                        time or false if it represents an end time.
+   */
+  void RemoveInstanceTime(SMILInstanceTime* aInstanceTime, bool aIsBegin);
+
+  /**
+   * Removes all the instance times associated with the given
+   * SMILTimeValueSpec object. Used when an ID assignment changes and hence
+   * all the previously associated instance times become invalid.
+   *
+   * @param aCreator The SMILTimeValueSpec object whose created
+   *                 SMILInstanceTime's should be removed.
+   * @param aIsBegin true if the times to be removed represent begin
+   *                 times or false if they are end times.
+   */
+  void RemoveInstanceTimesForCreator(const SMILTimeValueSpec* aCreator,
+                                     bool aIsBegin);
+
+  /**
+   * Sets the object that will be called by this timed element each time it is
+   * sampled.
+   *
+   * In Schmitz's model it is possible to associate several time clients with
+   * a timed element but for now we only allow one.
+   *
+   * @param aClient   The time client to associate. Any previous time client
+   *                  will be disassociated and no longer sampled. Setting this
+   *                  to nullptr will simply disassociate the previous client,
+   * if any.
+   */
+  void SetTimeClient(SMILAnimationFunction* aClient);
+
+  /**
+   * Samples the object at the given container time. Timing intervals are
+   * updated and if this element is active at the given time the associated time
+   * client will be sampled with the appropriate simple time.
+   *
+   * @param aContainerTime The container time at which to sample.
+   */
+  void SampleAt(SMILTime aContainerTime);
+
+  /**
+   * Performs a special sample for the end of an interval. Such a sample should
+   * only advance the timed element (and any dependent elements) to the waiting
+   * or postactive state. It should not cause a transition to the active state.
+   * Transition to the active state is only performed on a regular SampleAt.
+   *
+   * This allows all interval ends at a given time to be processed first and
+   * hence the new interval can be established based on full information of the
+   * available instance times.
+   *
+   * @param aContainerTime The container time at which to sample.
+   */
+  void SampleEndAt(SMILTime aContainerTime);
+
+  /**
+   * Informs the timed element that its time container has changed time
+   * relative to document time. The timed element therefore needs to update its
+   * dependent elements (which may belong to a different time container) so they
+   * can re-resolve their times.
+   */
+  void HandleContainerTimeChange();
+
+  /**
+   * Resets this timed element's accumulated times and intervals back to start
+   * up state.
+   *
+   * This is used for backwards seeking where rather than accumulating
+   * historical timing state and winding it back, we reset the element and seek
+   * forwards.
+   */
+  void Rewind();
+
+  /**
+   * Marks this element as disabled or not. If the element is disabled, it
+   * will ignore any future samples and discard any accumulated timing state.
+   *
+   * This is used by SVG to "turn off" timed elements when the associated
+   * animation element has failing conditional processing tests.
+   *
+   * Returns true if the disabled state of the timed element was changed
+   * as a result of this call (i.e. it was not a redundant call).
+   */
+  bool SetIsDisabled(bool aIsDisabled);
+
+  /**
+   * Attempts to set an attribute on this timed element.
+   *
+   * @param aAttribute  The name of the attribute to set. The namespace of this
+   *                    attribute is not specified as it is checked by the host
+   *                    element. Only attributes in the namespace defined for
+   *                    SMIL attributes in the host language are passed to the
+   *                    timed element.
+   * @param aValue      The attribute value.
+   * @param aResult     The nsAttrValue object that may be used for storing the
+   *                    parsed result.
+   * @param aContextElement The element to use for context when resolving
+   *                        references to other elements.
+   * @param[out] aParseResult The result of parsing the attribute. Will be set
+   *                          to NS_OK if parsing is successful.
+   *
+   * @return true if the given attribute is a timing attribute, false
+   * otherwise.
+   */
+  bool SetAttr(nsAtom* aAttribute, const nsAString& aValue,
+               nsAttrValue& aResult, Element& aContextElement,
+               nsresult* aParseResult = nullptr);
+
+  /**
+   * Attempts to unset an attribute on this timed element.
+   *
+   * @param aAttribute  The name of the attribute to set. As with SetAttr the
+   *                    namespace of the attribute is not specified (see
+   *                    SetAttr).
+   *
+   * @return true if the given attribute is a timing attribute, false
+   * otherwise.
+   */
+  bool UnsetAttr(nsAtom* aAttribute);
+
+  /**
+   * Adds a syncbase dependency to the list of dependents that will be notified
+   * when this timed element creates, deletes, or updates its current interval.
+   *
+   * @param aDependent  The SMILTimeValueSpec object to notify. A raw pointer
+   *                    to this object will be stored. Therefore it is necessary
+   *                    for the object to be explicitly unregistered (with
+   *                    RemoveDependent) when it is destroyed.
+   */
+  void AddDependent(SMILTimeValueSpec& aDependent);
+
+  /**
+   * Removes a syncbase dependency from the list of dependents that are notified
+   * when the current interval is modified.
+   *
+   * @param aDependent  The SMILTimeValueSpec object to unregister.
+   */
+  void RemoveDependent(SMILTimeValueSpec& aDependent);
+
+  /**
+   * Determines if this timed element is dependent on the given timed element's
+   * begin time for the interval currently in effect. Whilst the element is in
+   * the active state this is the current interval and in the postactive or
+   * waiting state this is the previous interval if one exists. In all other
+   * cases the element is not considered a time dependent of any other element.
+   *
+   * @param aOther    The potential syncbase element.
+   * @return true if this timed element's begin time for the currently
+   * effective interval is directly or indirectly derived from aOther, false
+   * otherwise.
+   */
+  bool IsTimeDependent(const SMILTimedElement& aOther) const;
+
+  /**
+   * Called when the timed element has been bound to the document so that
+   * references from this timed element to other elements can be resolved.
+   *
+   * @param aContextElement The element which provides the necessary context for
+   *                        resolving references. This is typically the element
+   *                        in the host language that owns this timed element.
+   */
+  void BindToTree(Element& aContextElement);
+
+  /**
+   * Called when the target of the animation has changed so that event
+   * registrations can be updated.
+   */
+  void HandleTargetElementChange(Element* aNewTarget);
+
+  /**
+   * Called when the timed element has been removed from a document so that
+   * references to other elements can be broken.
+   */
+  void DissolveReferences() { Unlink(); }
+
+  // Cycle collection
+  void Traverse(nsCycleCollectionTraversalCallback* aCallback);
+  void Unlink();
+
+  using RemovalTestFunction = bool (*)(SMILInstanceTime* aInstance);
+
+ protected:
+  // Typedefs
+  using TimeValueSpecList = nsTArray<UniquePtr<SMILTimeValueSpec>>;
+  using InstanceTimeList = nsTArray<RefPtr<SMILInstanceTime>>;
+  using IntervalList = nsTArray<UniquePtr<SMILInterval>>;
+  using TimeValueSpecPtrKey = nsPtrHashKey<SMILTimeValueSpec>;
+  using TimeValueSpecHashSet = nsTHashtable<TimeValueSpecPtrKey>;
+
+  // Helper classes
+  class InstanceTimeComparator {
+   public:
+    bool Equals(const SMILInstanceTime* aElem1,
+                const SMILInstanceTime* aElem2) const;
+    bool LessThan(const SMILInstanceTime* aElem1,
+                  const SMILInstanceTime* aElem2) const;
+  };
+
+  // Templated helper functions
+  template <class TestFunctor>
+  void RemoveInstanceTimes(InstanceTimeList& aArray, TestFunctor& aTest);
+
+  //
+  // Implementation helpers
+  //
+
+  nsresult SetBeginSpec(const nsAString& aBeginSpec, Element& aContextElement,
+                        RemovalTestFunction aRemove);
+  nsresult SetEndSpec(const nsAString& aEndSpec, Element& aContextElement,
+                      RemovalTestFunction aRemove);
+  nsresult SetSimpleDuration(const nsAString& aDurSpec);
+  nsresult SetMin(const nsAString& aMinSpec);
+  nsresult SetMax(const nsAString& aMaxSpec);
+  nsresult SetRestart(const nsAString& aRestartSpec);
+  nsresult SetRepeatCount(const nsAString& aRepeatCountSpec);
+  nsresult SetRepeatDur(const nsAString& aRepeatDurSpec);
+  nsresult SetFillMode(const nsAString& aFillModeSpec);
+
+  void UnsetBeginSpec(RemovalTestFunction aRemove);
+  void UnsetEndSpec(RemovalTestFunction aRemove);
+  void UnsetSimpleDuration();
+  void UnsetMin();
+  void UnsetMax();
+  void UnsetRestart();
+  void UnsetRepeatCount();
+  void UnsetRepeatDur();
+  void UnsetFillMode();
+
+  nsresult SetBeginOrEndSpec(const nsAString& aSpec, Element& aContextElement,
+                             bool aIsBegin, RemovalTestFunction aRemove);
+  void ClearSpecs(TimeValueSpecList& aSpecs, InstanceTimeList& aInstances,
+                  RemovalTestFunction aRemove);
+  void ClearIntervals();
+  void DoSampleAt(SMILTime aContainerTime, bool aEndOnly);
+
+  /**
+   * Helper function to check for an early end and, if necessary, update the
+   * current interval accordingly.
+   *
+   * See SMIL 3.0, section 5.4.5, Element life cycle, "Active Time - Playing an
+   * interval" for a description of ending early.
+   *
+   * @param aSampleTime The current sample time. Early ends should only be
+   *                    applied at the last possible moment (i.e. if they are at
+   *                    or before the current sample time) and only if the
+   *                    current interval is not already ending.
+   * @return true if the end time of the current interval was updated,
+   *         false otherwise.
+   */
+  bool ApplyEarlyEnd(const SMILTimeValue& aSampleTime);
+
+  /**
+   * Clears certain state in response to the element restarting.
+   *
+   * This state is described in SMIL 3.0, section 5.4.3, Resetting element state
+   */
+  void Reset();
+
+  /**
+   * Clears all accumulated timing state except for those instance times for
+   * which aRemove does not return true.
+   *
+   * Unlike the Reset method which only clears instance times, this clears the
+   * element's state, intervals (including current interval), and tells the
+   * client animation function to stop applying a result. In effect, it returns
+   * the element to its initial state but preserves any instance times excluded
+   * by the passed-in function.
+   */
+  void ClearTimingState(RemovalTestFunction aRemove);
+
+  /**
+   * Recreates timing state by re-applying begin/end attributes specified on
+   * the associated animation element.
+   *
+   * Note that this does not completely restore the information cleared by
+   * ClearTimingState since it leaves the element in the startup state.
+   * The element state will be updated on the next sample.
+   */
+  void RebuildTimingState(RemovalTestFunction aRemove);
+
+  /**
+   * Completes a seek operation by sending appropriate events and, in the case
+   * of a backwards seek, updating the state of timing information that was
+   * previously considered historical.
+   */
+  void DoPostSeek();
+
+  /**
+   * Unmarks instance times that were previously preserved because they were
+   * considered important historical milestones but are no longer such because
+   * a backwards seek has been performed.
+   */
+  void UnpreserveInstanceTimes(InstanceTimeList& aList);
+
+  /**
+   * Helper function to iterate through this element's accumulated timing
+   * information (specifically old SMILIntervals and SMILTimeInstanceTimes)
+   * and discard items that are no longer needed or exceed some threshold of
+   * accumulated state.
+   */
+  void FilterHistory();
+
+  // Helper functions for FilterHistory to clear old SMILIntervals and
+  // SMILInstanceTimes respectively.
+  void FilterIntervals();
+  void FilterInstanceTimes(InstanceTimeList& aList);
+
+  /**
+   * Calculates the next acceptable interval for this element after the
+   * specified interval, or, if no previous interval is specified, it will be
+   * the first interval with an end time after t=0.
+   *
+   * @see SMILANIM 3.6.8
+   *
+   * @param aPrevInterval   The previous interval used. If supplied, the first
+   *                        interval that begins after aPrevInterval will be
+   *                        returned. May be nullptr.
+   * @param aReplacedInterval The interval that is being updated (if any). This
+   *                        used to ensure we don't return interval endpoints
+   *                        that are dependent on themselves. May be nullptr.
+   * @param aFixedBeginTime The time to use for the start of the interval. This
+   *                        is used when only the endpoint of the interval
+   *                        should be updated such as when the animation is in
+   *                        the ACTIVE state. May be nullptr.
+   * @param[out] aResult    The next interval. Will be unchanged if no suitable
+   *                        interval was found (in which case false will be
+   *                        returned).
+   * @return  true if a suitable interval was found, false otherwise.
+   */
+  bool GetNextInterval(const SMILInterval* aPrevInterval,
+                       const SMILInterval* aReplacedInterval,
+                       const SMILInstanceTime* aFixedBeginTime,
+                       SMILInterval& aResult) const;
+  SMILInstanceTime* GetNextGreater(const InstanceTimeList& aList,
+                                   const SMILTimeValue& aBase,
+                                   int32_t& aPosition) const;
+  SMILInstanceTime* GetNextGreaterOrEqual(const InstanceTimeList& aList,
+                                          const SMILTimeValue& aBase,
+                                          int32_t& aPosition) const;
+  SMILTimeValue CalcActiveEnd(const SMILTimeValue& aBegin,
+                              const SMILTimeValue& aEnd) const;
+  SMILTimeValue GetRepeatDuration() const;
+  SMILTimeValue ApplyMinAndMax(const SMILTimeValue& aDuration) const;
+  SMILTime ActiveTimeToSimpleTime(SMILTime aActiveTime,
+                                  uint32_t& aRepeatIteration);
+  SMILInstanceTime* CheckForEarlyEnd(const SMILTimeValue& aContainerTime) const;
+  void UpdateCurrentInterval(bool aForceChangeNotice = false);
+  void SampleSimpleTime(SMILTime aActiveTime);
+  void SampleFillValue();
+  nsresult AddInstanceTimeFromCurrentTime(SMILTime aCurrentTime,
+                                          double aOffsetSeconds, bool aIsBegin);
+  void RegisterMilestone();
+  bool GetNextMilestone(SMILMilestone& aNextMilestone) const;
+
+  // Notification methods. Note that these notifications can result in nested
+  // calls to this same object. Therefore,
+  // (i)  we should not perform notification until this object is in
+  //      a consistent state to receive callbacks, and
+  // (ii) after calling these methods we must assume that the state of the
+  //      element may have changed.
+  void NotifyNewInterval();
+  void NotifyChangedInterval(SMILInterval* aInterval, bool aBeginObjectChanged,
+                             bool aEndObjectChanged);
+
+  void FireTimeEventAsync(EventMessage aMsg, int32_t aDetail);
+  const SMILInstanceTime* GetEffectiveBeginInstance() const;
+  const SMILInterval* GetPreviousInterval() const;
+  bool HasPlayed() const { return !mOldIntervals.IsEmpty(); }
+  bool HasClientInFillRange() const;
+  bool EndHasEventConditions() const;
+  bool AreEndTimesDependentOn(const SMILInstanceTime* aBase) const;
+
+  // Reset the current interval by first passing ownership to a temporary
+  // variable so that if Unlink() results in us receiving a callback,
+  // mCurrentInterval will be nullptr and we will be in a consistent state.
+  void ResetCurrentInterval() {
+    if (mCurrentInterval) {
+      // Transfer ownership to temp var. (This sets mCurrentInterval to null.)
+      auto interval = std::move(mCurrentInterval);
+      interval->Unlink();
+    }
+  }
+
+  //
+  // Members
+  //
+  mozilla::dom::SVGAnimationElement* mAnimationElement;  // [weak] won't outlive
+                                                         // owner
+  TimeValueSpecList mBeginSpecs;                         // [strong]
+  TimeValueSpecList mEndSpecs;                           // [strong]
+
+  SMILTimeValue mSimpleDur;
+
+  SMILRepeatCount mRepeatCount;
+  SMILTimeValue mRepeatDur;
+
+  SMILTimeValue mMin;
+  SMILTimeValue mMax;
+
+  enum SMILFillMode : uint8_t { FILL_REMOVE, FILL_FREEZE };
+  SMILFillMode mFillMode;
+  static const nsAttrValue::EnumTable sFillModeTable[];
+
+  enum SMILRestartMode : uint8_t {
+    RESTART_ALWAYS,
+    RESTART_WHENNOTACTIVE,
+    RESTART_NEVER
+  };
+  SMILRestartMode mRestartMode;
+  static const nsAttrValue::EnumTable sRestartModeTable[];
+
+  InstanceTimeList mBeginInstances;
+  InstanceTimeList mEndInstances;
+  uint32_t mInstanceSerialIndex;
+
+  SMILAnimationFunction* mClient;
+  UniquePtr<SMILInterval> mCurrentInterval;
+  IntervalList mOldIntervals;
+  uint32_t mCurrentRepeatIteration;
+  SMILMilestone mPrevRegisteredMilestone;
+  static const SMILMilestone sMaxMilestone;
+  static const uint8_t sMaxNumIntervals;
+  static const uint8_t sMaxNumInstanceTimes;
+
+  // Set of dependent time value specs to be notified when establishing a new
+  // current interval. Change notifications and delete notifications are handled
+  // by the interval.
+  //
+  // [weak] The SMILTimeValueSpec objects register themselves and unregister
+  // on destruction. Likewise, we notify them when we are destroyed.
+  TimeValueSpecHashSet mTimeDependents;
+
+  /**
+   * The state of the element in its life-cycle. These states are based on the
+   * element life-cycle described in SMILANIM 3.6.8
+   */
+  enum SMILElementState {
+    STATE_STARTUP,
+    STATE_WAITING,
+    STATE_ACTIVE,
+    STATE_POSTACTIVE
+  };
+  SMILElementState mElementState;
+
+  enum SMILSeekState {
+    SEEK_NOT_SEEKING,
+    SEEK_FORWARD_FROM_ACTIVE,
+    SEEK_FORWARD_FROM_INACTIVE,
+    SEEK_BACKWARD_FROM_ACTIVE,
+    SEEK_BACKWARD_FROM_INACTIVE
+  };
+  SMILSeekState mSeekState;
+
+  // Used to batch updates to the timing model
+  class AutoIntervalUpdateBatcher;
+  bool mDeferIntervalUpdates;
+  bool mDoDeferredUpdate;  // Set if an update to the current interval was
+                           // requested while mDeferIntervalUpdates was set
+  bool mIsDisabled;
+
+  // Stack-based helper class to call UpdateCurrentInterval when it is destroyed
+  class AutoIntervalUpdater;
+
+  // Recursion depth checking
+  uint8_t mDeleteCount;
+  uint8_t mUpdateIntervalRecursionDepth;
+  static const uint8_t sMaxUpdateIntervalRecursionDepth;
+};
+
+inline void ImplCycleCollectionUnlink(SMILTimedElement& aField) {
+  aField.Unlink();
+}
+
+inline void ImplCycleCollectionTraverse(
+    nsCycleCollectionTraversalCallback& aCallback, SMILTimedElement& aField,
+    const char* aName, uint32_t aFlags = 0) {
+  aField.Traverse(&aCallback);
+}
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILTIMEDELEMENT_H_
diff --git a/dom/smil/SMILType.h b/dom/smil/SMILType.h
new file mode 100644
index 0000000000..5aef1e7623
--- /dev/null
+++ b/dom/smil/SMILType.h
@@ -0,0 +1,212 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILTYPE_H_
+#define DOM_SMIL_SMILTYPE_H_
+
+#include "mozilla/Attributes.h"
+#include "nscore.h"
+
+namespace mozilla {
+
+class SMILValue;
+
+//////////////////////////////////////////////////////////////////////////////
+// SMILType: Interface for defining the basic operations needed for animating
+// a particular kind of data (e.g. lengths, colors, transformation matrices).
+//
+// This interface is never used directly but always through a SMILValue that
+// bundles together a pointer to a concrete implementation of this interface and
+// the data upon which it should operate.
+//
+// We keep the data and type separate rather than just providing different
+// subclasses of SMILValue. This is so that sizeof(SMILValue) is the same
+// for all value types, allowing us to have a type-agnostic nsTArray of
+// SMILValue objects (actual objects, not pointers). It also allows most
+// SMILValues (except those that need to allocate extra memory for their
+// data) to be allocated on the stack and directly assigned to one another
+// provided performance benefits for the animation code.
+//
+// Note that different types have different capabilities. Roughly speaking there
+// are probably three main types:
+//
+// +---------------------+---------------+-------------+------------------+
+// | CATEGORY:           | DISCRETE      | LINEAR      | ADDITIVE         |
+// +---------------------+---------------+-------------+------------------+
+// | Example:            | strings,      | path data?  | lengths,         |
+// |                     | color k/words?|             | RGB color values |
+// |                     |               |             |                  |
+// | -- Assign?          |     X         |    X        |    X             |
+// | -- Add?             |     -         |    X?       |    X             |
+// | -- SandwichAdd?     |     -         |    -?       |    X             |
+// | -- ComputeDistance? |     -         |    -        |    X?            |
+// | -- Interpolate?     |     -         |    X        |    X             |
+// +---------------------+---------------+-------------+------------------+
+//
+
+class SMILType {
+  /**
+   * Only give the SMILValue class access to this interface.
+   */
+  friend class SMILValue;
+
+ protected:
+  /**
+   * Initialises aValue and sets it to some identity value such that adding
+   * aValue to another value of the same type has no effect.
+   *
+   * @pre  aValue.IsNull()
+   * @post aValue.mType == this
+   */
+  virtual void Init(SMILValue& aValue) const = 0;
+
+  /**
+   * Destroys any data associated with a value of this type.
+   *
+   * @pre  aValue.mType == this
+   * @post aValue.IsNull()
+   */
+  virtual void Destroy(SMILValue& aValue) const = 0;
+
+  /**
+   * Assign this object the value of another. Think of this as the assignment
+   * operator.
+   *
+   * @param   aDest       The left-hand side of the assignment.
+   * @param   aSrc        The right-hand side of the assignment.
+   * @return  NS_OK on success, an error code on failure such as when the
+   *          underlying type of the specified object differs.
+   *
+   * @pre aDest.mType == aSrc.mType == this
+   */
+  virtual nsresult Assign(SMILValue& aDest, const SMILValue& aSrc) const = 0;
+
+  /**
+   * Test two SMILValue objects (of this SMILType) for equality.
+   *
+   * A return value of true represents a guarantee that aLeft and aRight are
+   * equal. (That is, they would behave identically if passed to the methods
+   * Add, SandwichAdd, ComputeDistance, and Interpolate).
+   *
+   * A return value of false simply indicates that we make no guarantee
+   * about equality.
+   *
+   * NOTE: It's perfectly legal for implementations of this method to return
+   * false in all cases.  However, smarter implementations will make this
+   * method more useful for optimization.
+   *
+   * @param   aLeft       The left-hand side of the equality check.
+   * @param   aRight      The right-hand side of the equality check.
+   * @return  true if we're sure the values are equal, false otherwise.
+   *
+   * @pre aDest.mType == aSrc.mType == this
+   */
+  virtual bool IsEqual(const SMILValue& aLeft,
+                       const SMILValue& aRight) const = 0;
+
+  /**
+   * Adds two values.
+   *
+   * The count parameter facilitates repetition.
+   *
+   * By equation,
+   *
+   *   aDest += aValueToAdd * aCount
+   *
+   * Therefore, if aCount == 0, aDest will be unaltered.
+   *
+   * This method will fail if this data type is not additive or the value was
+   * not specified using an additive syntax.
+   *
+   * See SVG 1.1, section 19.2.5. In particular,
+   *
+   *   "If a given attribute or property can take values of keywords (which are
+   *   not additive) or numeric values (which are additive), then additive
+   *   animations are possible if the subsequent animation uses a numeric value
+   *   even if the base animation uses a keyword value; however, if the
+   *   subsequent animation uses a keyword value, additive animation is not
+   *   possible."
+   *
+   * If this method fails (e.g. because the data type is not additive), aDest
+   * will be unaltered.
+   *
+   * @param   aDest       The value to add to.
+   * @param   aValueToAdd The value to add.
+   * @param   aCount      The number of times to add aValueToAdd.
+   * @return  NS_OK on success, an error code on failure.
+   *
+   * @pre aValueToAdd.mType == aDest.mType == this
+   */
+  virtual nsresult Add(SMILValue& aDest, const SMILValue& aValueToAdd,
+                       uint32_t aCount) const = 0;
+
+  /**
+   * Adds aValueToAdd to the underlying value in the animation sandwich, aDest.
+   *
+   * For most types this operation is identical to a regular Add() but for some
+   * types (notably <animateTransform>) the operation differs. For
+   * <animateTransform> Add() corresponds to simply adding together the
+   * transform parameters and is used when calculating cumulative values or
+   * by-animation values. On the other hand SandwichAdd() is used when adding to
+   * the underlying value and requires matrix post-multiplication. (This
+   * distinction is most clearly indicated by the SVGT1.2 test suite. It is not
+   * obvious within the SMIL specifications.)
+   *
+   * @param   aDest       The value to add to.
+   * @param   aValueToAdd The value to add.
+   * @return  NS_OK on success, an error code on failure.
+   *
+   * @pre aValueToAdd.mType == aDest.mType == this
+   */
+  virtual nsresult SandwichAdd(SMILValue& aDest,
+                               const SMILValue& aValueToAdd) const {
+    return Add(aDest, aValueToAdd, 1);
+  }
+
+  /**
+   * Calculates the 'distance' between two values. This is the distance used in
+   * paced interpolation.
+   *
+   * @param   aFrom     The start of the interval for which the distance should
+   *                    be calculated.
+   * @param   aTo       The end of the interval for which the distance should be
+   *                    calculated.
+   * @param   aDistance The result of the calculation.
+   * @return  NS_OK on success, or an appropriate error code if there is no
+   *          notion of distance for the underlying data type or the distance
+   *          could not be calculated.
+   *
+   * @pre aFrom.mType == aTo.mType == this
+   */
+  virtual nsresult ComputeDistance(const SMILValue& aFrom, const SMILValue& aTo,
+                                   double& aDistance) const = 0;
+
+  /**
+   * Calculates an interpolated value between two values using the specified
+   * proportion.
+   *
+   * @param   aStartVal     The value defining the start of the interval of
+   *                        interpolation.
+   * @param   aEndVal       The value defining the end of the interval of
+   *                        interpolation.
+   * @param   aUnitDistance A number between 0.0 and 1.0 (inclusive) defining
+   *                        the distance of the interpolated value in the
+   *                        interval.
+   * @param   aResult       The interpolated value.
+   * @return  NS_OK on success, NS_ERROR_FAILURE if this data type cannot be
+   *          interpolated or NS_ERROR_OUT_OF_MEMORY if insufficient memory was
+   *          available for storing the result.
+   *
+   * @pre aStartVal.mType == aEndVal.mType == aResult.mType == this
+   */
+  virtual nsresult Interpolate(const SMILValue& aStartVal,
+                               const SMILValue& aEndVal, double aUnitDistance,
+                               SMILValue& aResult) const = 0;
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILTYPE_H_
diff --git a/dom/smil/SMILTypes.h b/dom/smil/SMILTypes.h
new file mode 100644
index 0000000000..6391872f9e
--- /dev/null
+++ b/dom/smil/SMILTypes.h
@@ -0,0 +1,30 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILTYPES_H_
+#define DOM_SMIL_SMILTYPES_H_
+
+#include <stdint.h>
+
+namespace mozilla {
+
+// A timestamp in milliseconds
+//
+// A time may represent:
+//
+//   simple time -- offset within the simple duration
+//   active time -- offset within the active duration
+//   document time -- offset since the document begin
+//   wallclock time -- "real" time -- offset since the epoch
+//
+// For an overview of how this class is related to other SMIL time classes see
+// the documentation in SMILTimeValue.h
+//
+using SMILTime = int64_t;
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILTYPES_H_
diff --git a/dom/smil/SMILValue.cpp b/dom/smil/SMILValue.cpp
new file mode 100644
index 0000000000..4942e3b8b6
--- /dev/null
+++ b/dom/smil/SMILValue.cpp
@@ -0,0 +1,142 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SMILValue.h"
+
+#include "nsDebug.h"
+#include <string.h>
+
+namespace mozilla {
+
+//----------------------------------------------------------------------
+// Public methods
+
+SMILValue::SMILValue(const SMILType* aType) : mType(SMILNullType::Singleton()) {
+  mU.mBool = false;
+  if (!aType) {
+    NS_ERROR("Trying to construct SMILValue with null mType pointer");
+    return;
+  }
+
+  InitAndCheckPostcondition(aType);
+}
+
+SMILValue::SMILValue(const SMILValue& aVal) : mType(SMILNullType::Singleton()) {
+  InitAndCheckPostcondition(aVal.mType);
+  mType->Assign(*this, aVal);
+}
+
+const SMILValue& SMILValue::operator=(const SMILValue& aVal) {
+  if (&aVal == this) return *this;
+
+  if (mType != aVal.mType) {
+    DestroyAndReinit(aVal.mType);
+  }
+
+  mType->Assign(*this, aVal);
+
+  return *this;
+}
+
+// Move constructor / reassignment operator:
+SMILValue::SMILValue(SMILValue&& aVal) noexcept
+    : mU(aVal.mU),  // Copying union is only OK because we clear aVal.mType
+                    // below.
+      mType(aVal.mType) {
+  // Leave aVal with a null type, so that it's safely destructible (and won't
+  // mess with anything referenced by its union, which we've copied).
+  aVal.mType = SMILNullType::Singleton();
+}
+
+SMILValue& SMILValue::operator=(SMILValue&& aVal) noexcept {
+  if (!IsNull()) {
+    // Clean up any data we're currently tracking.
+    DestroyAndCheckPostcondition();
+  }
+
+  // Copy the union (which could include a pointer to external memory) & mType:
+  mU = aVal.mU;
+  mType = aVal.mType;
+
+  // Leave aVal with a null type, so that it's safely destructible (and won't
+  // mess with anything referenced by its union, which we've now copied).
+  aVal.mType = SMILNullType::Singleton();
+
+  return *this;
+}
+
+bool SMILValue::operator==(const SMILValue& aVal) const {
+  if (&aVal == this) return true;
+
+  return mType == aVal.mType && mType->IsEqual(*this, aVal);
+}
+
+nsresult SMILValue::Add(const SMILValue& aValueToAdd, uint32_t aCount) {
+  if (aValueToAdd.mType != mType) {
+    NS_ERROR("Trying to add incompatible types");
+    return NS_ERROR_FAILURE;
+  }
+
+  return mType->Add(*this, aValueToAdd, aCount);
+}
+
+nsresult SMILValue::SandwichAdd(const SMILValue& aValueToAdd) {
+  if (aValueToAdd.mType != mType) {
+    NS_ERROR("Trying to add incompatible types");
+    return NS_ERROR_FAILURE;
+  }
+
+  return mType->SandwichAdd(*this, aValueToAdd);
+}
+
+nsresult SMILValue::ComputeDistance(const SMILValue& aTo,
+                                    double& aDistance) const {
+  if (aTo.mType != mType) {
+    NS_ERROR("Trying to calculate distance between incompatible types");
+    return NS_ERROR_FAILURE;
+  }
+
+  return mType->ComputeDistance(*this, aTo, aDistance);
+}
+
+nsresult SMILValue::Interpolate(const SMILValue& aEndVal, double aUnitDistance,
+                                SMILValue& aResult) const {
+  if (aEndVal.mType != mType) {
+    NS_ERROR("Trying to interpolate between incompatible types");
+    return NS_ERROR_FAILURE;
+  }
+
+  if (aResult.mType != mType) {
+    // Outparam has wrong type
+    aResult.DestroyAndReinit(mType);
+  }
+
+  return mType->Interpolate(*this, aEndVal, aUnitDistance, aResult);
+}
+
+//----------------------------------------------------------------------
+// Helper methods
+
+// Wrappers for SMILType::Init & ::Destroy that verify their postconditions
+void SMILValue::InitAndCheckPostcondition(const SMILType* aNewType) {
+  aNewType->Init(*this);
+  MOZ_ASSERT(mType == aNewType,
+             "Post-condition of Init failed. SMILValue is invalid");
+}
+
+void SMILValue::DestroyAndCheckPostcondition() {
+  mType->Destroy(*this);
+  MOZ_ASSERT(IsNull(),
+             "Post-condition of Destroy failed. "
+             "SMILValue not null after destroying");
+}
+
+void SMILValue::DestroyAndReinit(const SMILType* aNewType) {
+  DestroyAndCheckPostcondition();
+  InitAndCheckPostcondition(aNewType);
+}
+
+}  // namespace mozilla
diff --git a/dom/smil/SMILValue.h b/dom/smil/SMILValue.h
new file mode 100644
index 0000000000..d57daa5eb3
--- /dev/null
+++ b/dom/smil/SMILValue.h
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_SMILVALUE_H_
+#define DOM_SMIL_SMILVALUE_H_
+
+#include "mozilla/SMILNullType.h"
+#include "mozilla/SMILType.h"
+
+namespace mozilla {
+
+/**
+ * Although objects of this type are generally only created on the stack and
+ * only exist during the taking of a new time sample, that's not always the
+ * case. The SMILValue objects obtained from attributes' base values are
+ * cached so that the SMIL engine can make certain optimizations during a
+ * sample if the base value has not changed since the last sample (potentially
+ * avoiding recomposing). These SMILValue objects typically live much longer
+ * than a single sample.
+ */
+class SMILValue {
+ public:
+  SMILValue() : mU(), mType(SMILNullType::Singleton()) {}
+  explicit SMILValue(const SMILType* aType);
+  SMILValue(const SMILValue& aVal);
+
+  ~SMILValue() { mType->Destroy(*this); }
+
+  const SMILValue& operator=(const SMILValue& aVal);
+
+  // Move constructor / reassignment operator:
+  SMILValue(SMILValue&& aVal) noexcept;
+  SMILValue& operator=(SMILValue&& aVal) noexcept;
+
+  // Equality operators. These are allowed to be conservative (return false
+  // more than you'd expect) - see comment above SMILType::IsEqual.
+  bool operator==(const SMILValue& aVal) const;
+  bool operator!=(const SMILValue& aVal) const { return !(*this == aVal); }
+
+  bool IsNull() const { return (mType == SMILNullType::Singleton()); }
+
+  nsresult Add(const SMILValue& aValueToAdd, uint32_t aCount = 1);
+  nsresult SandwichAdd(const SMILValue& aValueToAdd);
+  nsresult ComputeDistance(const SMILValue& aTo, double& aDistance) const;
+  nsresult Interpolate(const SMILValue& aEndVal, double aUnitDistance,
+                       SMILValue& aResult) const;
+
+  union {
+    bool mBool;
+    uint64_t mUint;
+    int64_t mInt;
+    double mDouble;
+    struct {
+      float mAngle;
+      uint16_t mUnit;
+      uint16_t mOrientType;
+    } mOrient;
+    int32_t mIntPair[2];
+    float mNumberPair[2];
+    void* mPtr;
+  } mU;
+  const SMILType* mType;
+
+ protected:
+  void InitAndCheckPostcondition(const SMILType* aNewType);
+  void DestroyAndCheckPostcondition();
+  void DestroyAndReinit(const SMILType* aNewType);
+};
+
+}  // namespace mozilla
+
+#endif  // DOM_SMIL_SMILVALUE_H_
diff --git a/dom/smil/TimeEvent.cpp b/dom/smil/TimeEvent.cpp
new file mode 100644
index 0000000000..cbb6e72d92
--- /dev/null
+++ b/dom/smil/TimeEvent.cpp
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ContentEvents.h"
+#include "mozilla/dom/TimeEvent.h"
+#include "nsIDocShell.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsPresContext.h"
+#include "nsGlobalWindowInner.h"
+
+namespace mozilla::dom {
+
+TimeEvent::TimeEvent(EventTarget* aOwner, nsPresContext* aPresContext,
+                     InternalSMILTimeEvent* aEvent)
+    : Event(aOwner, aPresContext,
+            aEvent ? aEvent : new InternalSMILTimeEvent(false, eVoidEvent)),
+      mDetail(mEvent->AsSMILTimeEvent()->mDetail) {
+  if (aEvent) {
+    mEventIsInternal = false;
+  } else {
+    mEventIsInternal = true;
+  }
+
+  if (mPresContext) {
+    nsCOMPtr<nsIDocShell> docShell = mPresContext->GetDocShell();
+    if (docShell) {
+      mView = docShell->GetWindow();
+    }
+  }
+}
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(TimeEvent, Event, mView)
+
+NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED_0(TimeEvent, Event)
+
+void TimeEvent::InitTimeEvent(const nsAString& aType,
+                              nsGlobalWindowInner* aView, int32_t aDetail) {
+  NS_ENSURE_TRUE_VOID(!mEvent->mFlags.mIsBeingDispatched);
+
+  Event::InitEvent(aType, false /*doesn't bubble*/, false /*can't cancel*/);
+  mDetail = aDetail;
+  mView = aView ? aView->GetOuterWindow() : nullptr;
+}
+
+}  // namespace mozilla::dom
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+already_AddRefed<TimeEvent> NS_NewDOMTimeEvent(EventTarget* aOwner,
+                                               nsPresContext* aPresContext,
+                                               InternalSMILTimeEvent* aEvent) {
+  return do_AddRef(new TimeEvent(aOwner, aPresContext, aEvent));
+}
diff --git a/dom/smil/TimeEvent.h b/dom/smil/TimeEvent.h
new file mode 100644
index 0000000000..3b82e76378
--- /dev/null
+++ b/dom/smil/TimeEvent.h
@@ -0,0 +1,61 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_SMIL_TIMEEVENT_H_
+#define DOM_SMIL_TIMEEVENT_H_
+
+#include "nsDocShell.h"
+#include "mozilla/dom/Event.h"
+#include "mozilla/dom/TimeEventBinding.h"
+#include "mozilla/dom/Nullable.h"
+#include "mozilla/dom/WindowProxyHolder.h"
+
+class nsGlobalWindowInner;
+
+namespace mozilla::dom {
+
+class TimeEvent final : public Event {
+ public:
+  TimeEvent(EventTarget* aOwner, nsPresContext* aPresContext,
+            InternalSMILTimeEvent* aEvent);
+
+  // nsISupports interface:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(TimeEvent, Event)
+
+  JSObject* WrapObjectInternal(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) override {
+    return TimeEvent_Binding::Wrap(aCx, this, aGivenProto);
+  }
+
+  void InitTimeEvent(const nsAString& aType, nsGlobalWindowInner* aView,
+                     int32_t aDetail);
+
+  int32_t Detail() const { return mDetail; }
+
+  Nullable<WindowProxyHolder> GetView() const {
+    if (!mView) {
+      return nullptr;
+    }
+    return WindowProxyHolder(mView->GetBrowsingContext());
+  }
+
+  TimeEvent* AsTimeEvent() final { return this; }
+
+ private:
+  ~TimeEvent() = default;
+
+  nsCOMPtr<nsPIDOMWindowOuter> mView;
+  int32_t mDetail;
+};
+
+}  // namespace mozilla::dom
+
+already_AddRefed<mozilla::dom::TimeEvent> NS_NewDOMTimeEvent(
+    mozilla::dom::EventTarget* aOwner, nsPresContext* aPresContext,
+    mozilla::InternalSMILTimeEvent* aEvent);
+
+#endif  // DOM_SMIL_TIMEEVENT_H_
diff --git a/dom/smil/crashtests/1010681-1.svg b/dom/smil/crashtests/1010681-1.svg
new file mode 100644
index 0000000000..882bcb53fe
--- /dev/null
+++ b/dom/smil/crashtests/1010681-1.svg
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg"
+     class="reftest-wait">
+<script>
+<![CDATA[
+
+function boom()
+{
+  var animate =
+    document.createElementNS("http://www.w3.org/2000/svg", "animate");
+  animate.setAttribute("dur", "2s");
+  document.documentElement.appendChild(animate);
+  animate.targetElement;
+  animate.requiredExtensions.insertItemBefore(0, 0);
+  document.documentElement.setCurrentTime(4);
+  document.documentElement.setCurrentTime(0);
+  document.documentElement.removeAttribute("class");
+}
+
+window.addEventListener("load", boom, false);
+
+]]>
+</script></svg>
diff --git a/dom/smil/crashtests/1322770-1.svg b/dom/smil/crashtests/1322770-1.svg
new file mode 100644
index 0000000000..405435184e
--- /dev/null
+++ b/dom/smil/crashtests/1322770-1.svg
@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+  <animateMotion keyTimes='.1;.6;.6' path='m0,1l7,3' keyPoints='.6;1;.7'/>
+</svg>
diff --git a/dom/smil/crashtests/1322849-1.svg b/dom/smil/crashtests/1322849-1.svg
new file mode 100644
index 0000000000..ea3d629813
--- /dev/null
+++ b/dom/smil/crashtests/1322849-1.svg
@@ -0,0 +1,2 @@
+<svg>
+<set fill='freeze' dur='8' repeatCount='1844674737095516'>
diff --git a/dom/smil/crashtests/1343357-1.html b/dom/smil/crashtests/1343357-1.html
new file mode 100644
index 0000000000..8219c31221
--- /dev/null
+++ b/dom/smil/crashtests/1343357-1.html
@@ -0,0 +1,12 @@
+<svg>
+  <animateMotion to="500,500"></animateMotion>
+  <animateMotion to="10,40"></animateMotion>
+</svg>
+<svg width="100" height="100">
+  <rect width="100%" height="100%" />
+  <circle r="2" fill="red">
+    <animateMotion dur="1s" from="50,50" to="80,70" additive="sum"></animateMotion>
+    <animateMotion dur="1s" from="50,50" to="80,70" additive="sum"></animateMotion>
+    <animateMotion dur="3s" to="0,80"></animateMotion>
+  </circle>
+</svg>
diff --git a/dom/smil/crashtests/1375596-1.svg b/dom/smil/crashtests/1375596-1.svg
new file mode 100644
index 0000000000..69c1673d11
--- /dev/null
+++ b/dom/smil/crashtests/1375596-1.svg
@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="800" height="600">
+<animate by="2" min="5:45" calcMode="discrete" attributeName="height" />
+</svg>
diff --git a/dom/smil/crashtests/1402547-1.html b/dom/smil/crashtests/1402547-1.html
new file mode 100644
index 0000000000..28fa7ce185
--- /dev/null
+++ b/dom/smil/crashtests/1402547-1.html
@@ -0,0 +1,3 @@
+<svg>
+<animate id='a' calcMode='discrete' attributeName='height' by='-159'/>
+<animate id='a' calcMode='discrete' attributeName='height' by='-159'/>
diff --git a/dom/smil/crashtests/1411963-1.html b/dom/smil/crashtests/1411963-1.html
new file mode 100644
index 0000000000..cc61b73e2a
--- /dev/null
+++ b/dom/smil/crashtests/1411963-1.html
@@ -0,0 +1,10 @@
+<html>
+  <head>
+    <script>
+      const o1 = document.createElement('div');
+      document.querySelector('script').appendChild(o1);
+      document.writeln("<svg><animate to attributeName='width'>");
+      o1.innerHTML = "<meta http-equiv='Content-Security-Policy' content=default-src>";
+    </script>
+  </head>
+</html>
diff --git a/dom/smil/crashtests/1413319-1.html b/dom/smil/crashtests/1413319-1.html
new file mode 100644
index 0000000000..9bfeef3bdd
--- /dev/null
+++ b/dom/smil/crashtests/1413319-1.html
@@ -0,0 +1,2 @@
+<svg width=''>
+<animate dur='2ms' repeatCount='4611686018427387903' fill='freeze'/>
diff --git a/dom/smil/crashtests/1535388-1.html b/dom/smil/crashtests/1535388-1.html
new file mode 100644
index 0000000000..cdfaba4d90
--- /dev/null
+++ b/dom/smil/crashtests/1535388-1.html
@@ -0,0 +1,18 @@
+<html>
+<head>
+<script>
+function start () {
+  document.location.assign('abc')
+  SpecialPowers.forceGC()
+  SpecialPowers.forceCC()
+  const XHR = new XMLHttpRequest()
+  XHR.open('GET', 'data:text/html,1', false)
+  XHR.send()
+}
+window.addEventListener('load', start)
+</script>
+</head>
+<body>
+<svg></svg>
+</body>
+</html>
diff --git a/dom/smil/crashtests/1772573-1.html b/dom/smil/crashtests/1772573-1.html
new file mode 100644
index 0000000000..ef7783e51b
--- /dev/null
+++ b/dom/smil/crashtests/1772573-1.html
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <script>
+      document.addEventListener('DOMContentLoaded', () => {
+        const svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg')
+        const path = document.createElementNS('http://www.w3.org/2000/svg', 'path')
+        const animate = document.createElementNS('http://www.w3.org/2000/svg', 'animate')
+        animate.setAttribute('attributeName', 'd')
+        animate.setAttribute('from', 'm 2 9 1419128296 127 -17291 41.63920880714647 100.9114622394993 64.9992192746583 186 -25 Z H -5030 62 127 2 127 127 -94990565 S 53 73 -4 245 127.53546217576341 27 154 83 74 -32 44674 139 -81 203 -75.80766604754885 9780 71 64 1 -76 t 126 184 -46 96')
+        animate.setAttribute('by', 'M -2339 0 Z H 64 s 2 47 175 -41 170.98160669377478 -9012 119 -135 1971 74 9 64 -43 100 1192512014 95 63 32 167 20 89 32 183 65 3102047877 127 120 32 -23430 -121 19 16 Q -102 24 -29 135 -7 -113 -82.85249539745232 113 -43 -29 82 200')
+        path.appendChild(animate)
+        svg.appendChild(path)
+        document.documentElement.appendChild(svg)
+      })
+    </script>
+</head>
+</html>
diff --git a/dom/smil/crashtests/1780800-1.html b/dom/smil/crashtests/1780800-1.html
new file mode 100644
index 0000000000..14129a627c
--- /dev/null
+++ b/dom/smil/crashtests/1780800-1.html
@@ -0,0 +1,22 @@
+<!DOCTYPE html>
+<html class="reftest-wait">
+<head>
+<script>
+document.addEventListener("DOMContentLoaded", () => {
+  const svg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
+  const set = document.createElementNS("http://www.w3.org/2000/svg", "set");
+  svg.appendChild(set);
+  document.documentElement.appendChild(svg);
+  const animation = new Animation();
+  animation.addEventListener("finish", () =>
+    svg.setAttribute("pointer-events", "visible")
+  );
+  animation.startTime = 2713;
+  document.addEventListener("DOMAttrModified", e => {
+    e.originalTarget.setCurrentTime(1.050520798894502e38);
+    document.documentElement.removeAttribute("class");
+  });
+});
+</script>
+</head>
+</html>
diff --git a/dom/smil/crashtests/483584-1.svg b/dom/smil/crashtests/483584-1.svg
new file mode 100644
index 0000000000..b9ded113ef
--- /dev/null
+++ b/dom/smil/crashtests/483584-1.svg
@@ -0,0 +1,8 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+     xmlns:xlink="http://www.w3.org/1999/xlink">
+  <g id="s">
+    <circle/>
+    <animateTransform attributeName="transform"/>
+  </g>
+  <use xlink:href="#s"/>
+</svg>
diff --git a/dom/smil/crashtests/483584-2.svg b/dom/smil/crashtests/483584-2.svg
new file mode 100644
index 0000000000..f5cbd7d466
--- /dev/null
+++ b/dom/smil/crashtests/483584-2.svg
@@ -0,0 +1,133 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- =====================================================================-->
+<!-- animate-elem-30-t.svg                                                -->
+<!--                                                                      -->
+<!-- Tests various types of animations on referenced elements.            -->
+<!--                                                                      -->
+<!-- Author : Ola Andersson,  22-Sep-2003                                 -->
+<!--======================================================================-->
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1 Tiny//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11-tiny.dtd">
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" baseProfile="tiny" id="svg-root" width="480" height="360" viewBox="0 0 480 360" onload="go()" class="reftest-wait">
+   <script>
+     function go() {
+       var svg = document.documentElement;
+       svg.pauseAnimations();
+
+       // Note: Animations in this testcase have begin="100" dur="3".
+
+       // Jump to partway through animation...
+       svg.setCurrentTime(102);
+
+       // ...and then (if we didn't hang) jump back to a pre-animation time.
+       svg.setCurrentTime(50);
+
+       // Signal that the test is complete:
+       svg.removeAttribute("class");
+    }
+   </script>
+   <g transform="translate(20) scale(1.3)">   
+      <!-- SILHOUETTES-->
+      <path d="M210 40 C210 40 210 100 170 190" fill="none" stroke="#b4b4b4"/>
+      <path d="M 171 188 l 10 -10 l -10 -4 z" fill="#b4b4b4" stroke="none"/>
+      <polyline fill="none" stroke="#b4b4b4" stroke-width="2" points="200,20 200,40 220,40 220,60"/>
+      <polyline transform="rotate(15)" fill="none" stroke="#b4b4b4" stroke-width="9" points="200,120 200,140 220,140 220,160"/>
+  
+      <line x1="40" y1="50" x2="20" y2="10" stroke="#b4b4b4" stroke-width="3"/>
+      <line x1="160" y1="50" x2="80" y2="10" stroke="#b4b4b4" stroke-width="3"/>
+      <line x1="30" y1="30" x2="120" y2="30" stroke="#b4b4b4"/>
+      <path d="M 120 30 l -10 3 l 0 -6 z" fill="#b4b4b4" stroke="none"/>
+  
+      <line x1="70" y1="70" x2="145" y2="70" stroke="#b4b4b4"/>    
+      <rect x="10" y="60" width="60" height="20" fill="#b4b4b4" stroke="#b4b4b4" stroke-width="2"/>
+      <rect x="145" y="60" width="30" height="40" fill="#b4b4b4" stroke="#b4b4b4" stroke-width="2"/>
+      <path d="M 145 70 l -10 3 l 0 -6 z" fill="#b4b4b4" stroke="none"/>
+  
+      <circle cx="30" cy="100" r="10" fill="#b4b4b4" stroke="#b4b4b4"/>
+      <circle cx="100" cy="195" r="15" fill="#b4b4b4" stroke="#b4b4b4"/>
+      <line x1="37" y1="107" x2="89" y2="184" stroke="#b4b4b4"/>
+      <path d="M 90 185 l -3 -12 l -6 5 z" fill="#b4b4b4" stroke="none"/>
+   
+      <rect x="300" y="10" width="20" height="20" fill="#b4b4b4" stroke="#b4b4b4" stroke-width="2"/>
+      <rect x="300" y="170" width="20" height="40" fill="#b4b4b4" stroke="#b4b4b4" stroke-width="2"/>
+      <line x1="310" y1="30" x2="310" y2="170" stroke="#b4b4b4"/>
+      <path d="M 310 170 l -3 -10 l 6 0 z" fill="#b4b4b4" stroke="none"/>
+   
+      <rect x="230" y="7.5" width="40" height="7.5" fill="#b4b4b4" stroke="none"/>
+      <rect x="230" y="170" width="40" height="30" fill="#b4b4b4" stroke="none"/>
+      <line x1="250" y1="10" x2="250" y2="170" stroke="#b4b4b4"/>
+      <path d="M 250 170 l -3 -10 l 6 0 z" fill="#b4b4b4" stroke="none"/>
+      <!-- END OF SILHOUETTES-->
+      
+      <!-- DEFS-->
+      <defs>
+         <line id="lineID" x1="30" y1="50" x2="10" y2="10" stroke="rgb(16, 93, 140)" stroke-width="3">
+            <animate attributeName="x1" from="30" to="90" begin="100" dur="3" fill="freeze"/>
+         </line>
+      </defs>
+   
+      <defs>
+         <rect id="rectID" x="10" y="60" width="60" height="20" fill="blue" stroke="black" stroke-width="2">
+            <animateColor attributeName="fill" from="white" to="rgb(16, 93, 140)" begin="100" dur="3" fill="freeze"/>
+            <animate attributeName="height" from="20" to="40" begin="100" dur="3" fill="freeze"/>
+         </rect>
+      </defs>
+   
+      <defs>
+         <circle id="circleID" cx="20" cy="100" r="10" fill="rgb(16, 93, 140)" stroke="black" transform="">
+            <animate attributeName="cy" from="100" to="130" begin="100" dur="3" fill="freeze"/>
+            <animateTransform attributeName="transform" type="scale" from="1" to="1.5" additive="sum" begin="100" dur="3" fill="freeze"/>
+         </circle>
+      </defs>
+   
+      <defs>
+         <polyline id="polylineID" fill="none" stroke="rgb(16, 93, 140)" stroke-width="2" points="200,20 200,40 220,40 220,60">
+            <animateMotion path="M 0 0 l 0 100" begin="100" dur="3" fill="freeze"/>
+            <animate attributeName="stroke-width" from="2" to="9" begin="100" dur="3" fill="freeze"/>
+         </polyline>
+      </defs>
+   
+      <defs>
+         <polygon id="polygonID" fill="green" stroke="black" points="240,20 240,40 260,40 260,20" stroke-width="2">   
+            <animate attributeName="fill" from="white" to="rgb(16, 93, 140)" begin="100" dur="3" fill="freeze"/>
+         </polygon>
+      </defs>
+   
+      <defs>
+         <image id="imageID" x="230" y="20" width="40" height="80" 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">
+            <animate attributeName="y" from="5" to="145" begin="100" dur="3" fill="freeze"/>
+         </image>
+      </defs>      
+      <!-- END OF DEFS-->
+      
+      <!-- ACTUAL TEST CONTENT-->
+      <use xlink:href="#lineID">
+         <animate attributeName="x" from="10" to="70" begin="100" dur="3" fill="freeze"/>
+      </use>   
+      
+      <use xlink:href="#rectID" transform="">
+         <animateTransform attributeName="transform" type="translate" from="0 0" to="140 0" begin="100" dur="3" fill="freeze"/>
+         <animateTransform attributeName="transform" type="scale" from="1 1" to="0.5 1" begin="100" dur="3" additive="sum" fill="freeze"/>
+      </use>   
+   
+      <use xlink:href="#circleID">
+         <animate attributeName="x" from="10" to="70" begin="100" dur="3" fill="freeze"/>
+      </use>
+   
+      <use xlink:href="#polylineID" transform="">
+         <animateTransform attributeName="transform" type="rotate" from="0" to="15" additive="sum" begin="100" dur="3" fill="freeze"/>
+      </use>   
+   
+      <use x="60" y="-10" xlink:href="#polygonID" transform="">
+         <animateMotion path="M 0 0 l 0 150" begin="100" dur="3" fill="freeze"/>
+         <animateTransform attributeName="transform" type="scale" from="1 1" to="1 2" begin="100" dur="3" additive="sum" fill="freeze"/>
+      </use>
+   
+      <use xlink:href="#imageID" transform="">
+         <animateTransform attributeName="transform" type="scale" from="1 .25" to="1 1" begin="100" dur="3" additive="sum" fill="freeze"/>
+      </use>
+      <!-- END OF ACTUAL TEST CONTENT-->
+   </g>
+   
+   <text id="revision" x="10" y="340" font-size="40" stroke="none" fill="black">$Revision: 1.6 $</text>
+   <rect id="test-frame" x="1" y="1" width="478" height="358" fill="none" stroke="#000000"/>
+</svg>
diff --git a/dom/smil/crashtests/523188-1.svg b/dom/smil/crashtests/523188-1.svg
new file mode 100644
index 0000000000..c03cea4923
--- /dev/null
+++ b/dom/smil/crashtests/523188-1.svg
@@ -0,0 +1,15 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg"
+     class="reftest-wait"
+     onload="setTimeout(removeNode, 0)">
+  <script>
+    function removeNode() {
+      var node = document.getElementById("myRect");
+      node.parentNode.removeChild(node);
+      document.documentElement.removeAttribute("class");
+    }
+  </script>
+  <rect id="myRect" x="20" y="20" height="50" width="50" stroke="blue">
+    <animate attributeName="stroke-width" from="1" to="9" begin="0s" dur="2s"/>
+  </rect>
+</svg>
diff --git a/dom/smil/crashtests/525099-1.svg b/dom/smil/crashtests/525099-1.svg
new file mode 100644
index 0000000000..8eed11489a
--- /dev/null
+++ b/dom/smil/crashtests/525099-1.svg
@@ -0,0 +1,7 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg">
+  <rect x="20" y="20" height="50" width="50" fill="blue">
+    <animate attributeName="display" by="inline"
+             begin="0s" dur="1s"/>
+  </rect>
+</svg>
diff --git a/dom/smil/crashtests/526536-1.svg b/dom/smil/crashtests/526536-1.svg
new file mode 100644
index 0000000000..4fcf35d081
--- /dev/null
+++ b/dom/smil/crashtests/526536-1.svg
@@ -0,0 +1,19 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+     class="reftest-wait"
+     onload="setTimeout('boom()', 0)">
+<script type="text/javascript">
+<![CDATA[
+function boom()
+{
+  document.getElementById("anim").setAttribute("fill", "freeze");
+  document.documentElement.removeAttribute("class");
+}
+]]>
+</script>
+  <g transform="translate(50 50)">
+    <circle r="40" style="fill: yellow; stroke: black; stroke-width: 1">
+      <animate id="anim" attributeName="cx" attributeType="XML"
+        values="0; 200" dur="2s" begin="-1s" repeatCount="0.5"/>
+    </circle>
+  </g>
+</svg>
diff --git a/dom/smil/crashtests/526875-1.svg b/dom/smil/crashtests/526875-1.svg
new file mode 100644
index 0000000000..281454bf61
--- /dev/null
+++ b/dom/smil/crashtests/526875-1.svg
@@ -0,0 +1,4 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg">
+  <animate attributeName="fill-opacity" by="-1"/>
+</svg>
diff --git a/dom/smil/crashtests/526875-2.svg b/dom/smil/crashtests/526875-2.svg
new file mode 100644
index 0000000000..73c229da5f
--- /dev/null
+++ b/dom/smil/crashtests/526875-2.svg
@@ -0,0 +1,4 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg">
+  <animate attributeName="fill-opacity" by="1"/>
+</svg>
diff --git a/dom/smil/crashtests/529387-1-helper.svg b/dom/smil/crashtests/529387-1-helper.svg
new file mode 100644
index 0000000000..7885ab71fd
--- /dev/null
+++ b/dom/smil/crashtests/529387-1-helper.svg
@@ -0,0 +1,5 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+  <text y="20pt">abc
+    <animate attributeName="opacity" from="1" to="0" begin="0s" dur="2s"/>
+  </text>
+</svg>
diff --git a/dom/smil/crashtests/529387-1.xhtml b/dom/smil/crashtests/529387-1.xhtml
new file mode 100644
index 0000000000..de3dbec34c
--- /dev/null
+++ b/dom/smil/crashtests/529387-1.xhtml
@@ -0,0 +1,7 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+  <script>
+    var p = new XMLHttpRequest();
+    p.open("GET", "529387-1-helper.svg", false);
+    p.send();
+  </script>
+</html>
diff --git a/dom/smil/crashtests/531550-1.svg b/dom/smil/crashtests/531550-1.svg
new file mode 100644
index 0000000000..306f41702d
--- /dev/null
+++ b/dom/smil/crashtests/531550-1.svg
@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+  <g><animateTransform attributeName="transform" by="1"/></g>
+</svg>
diff --git a/dom/smil/crashtests/541297-1.svg b/dom/smil/crashtests/541297-1.svg
new file mode 100644
index 0000000000..4268232ba1
--- /dev/null
+++ b/dom/smil/crashtests/541297-1.svg
@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg"><svg id="w"><animate/></svg><script type="text/javascript">
+<![CDATA[
+
+function boom()
+{
+  anim = document.createElementNS("http://www.w3.org/2000/svg", "animate");
+  document.documentElement.appendChild(anim);
+  document.documentElement.removeChild(anim);
+  
+  setTimeout(t, 0);
+  
+  function t()
+  {
+    document.getElementById("w").appendChild(anim);
+  }
+}
+
+window.addEventListener("load", boom, false);
+
+]]>
+</script></svg>
diff --git a/dom/smil/crashtests/547333-1.svg b/dom/smil/crashtests/547333-1.svg
new file mode 100644
index 0000000000..bac629b493
--- /dev/null
+++ b/dom/smil/crashtests/547333-1.svg
@@ -0,0 +1,22 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg"
+     class="reftest-wait">
+<script type="text/javascript">
+<![CDATA[
+
+function boom()
+{
+  document.getElementsByTagName("animate")[0].setAttributeNS(null, "attributeName", "font-size");
+  document.getElementsByTagName("text")[0].setAttributeNS(null, "fill", "green");
+  document.documentElement.removeAttributeNS(null, "x");
+  document.documentElement.removeAttribute("class");
+}
+
+window.addEventListener("load", boom, false);
+
+]]>
+</script>
+
+<text>abc<animate/></text>
+
+</svg>
diff --git a/dom/smil/crashtests/548899-1.svg b/dom/smil/crashtests/548899-1.svg
new file mode 100644
index 0000000000..c12ed27454
--- /dev/null
+++ b/dom/smil/crashtests/548899-1.svg
@@ -0,0 +1,14 @@
+<?xml version="1.0"?>

+<svg xmlns="http://www.w3.org/2000/svg"

+     xmlns:xlink="http://www.w3.org/1999/xlink">

+  <defs>

+    <circle id="circleID" cx="20" cy="100" r="10" fill="orange" stroke="black">

+      <animateTransform attributeName="transform" type="scale"

+                        from="1" to="2" begin="0" dur="3"/>

+    </circle>

+    <rect id="rectID" fill="green" stroke="black" height="100" width="100">

+      <animate attributeName="fill" from="white" to="blue" begin="0" dur="3"/>

+    </rect>

+  </defs>

+  <use xlink:href="#circleID"/>

+</svg>

diff --git a/dom/smil/crashtests/551620-1.svg b/dom/smil/crashtests/551620-1.svg
new file mode 100644
index 0000000000..2ea83e9c29
--- /dev/null
+++ b/dom/smil/crashtests/551620-1.svg
@@ -0,0 +1,21 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+
+<animate id="x" begin="y.end"/>
+<animate id="y"/>
+
+<script>
+
+function boom()
+{
+  var x = document.getElementById("x");
+  var y = document.getElementById("y");
+  y.appendChild(x);
+  y.setAttributeNS(null, "dur", "0.5s");
+  y.removeAttributeNS(null, "dur");
+}
+
+window.addEventListener("load", boom, false);
+
+</script>
+
+</svg>
diff --git a/dom/smil/crashtests/554141-1.svg b/dom/smil/crashtests/554141-1.svg
new file mode 100644
index 0000000000..61ce419f53
--- /dev/null
+++ b/dom/smil/crashtests/554141-1.svg
@@ -0,0 +1,12 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+     onload="
+        document.documentElement.pauseAnimations();
+        document.documentElement.setCurrentTime(0);
+        document.getElementById('b').removeAttribute('begin');
+        document.getElementById('a').setAttribute('dur', '1s')">
+  <rect>
+    <animate attributeName="y" attributeType="XML" id="a"/>
+    <animate attributeName="fill" attributeType="CSS" id="b"
+      begin="a.end" dur="2s"/>
+  </rect>
+</svg>
diff --git a/dom/smil/crashtests/554202-2.svg b/dom/smil/crashtests/554202-2.svg
new file mode 100644
index 0000000000..a3bbb3195c
--- /dev/null
+++ b/dom/smil/crashtests/554202-2.svg
@@ -0,0 +1,19 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+     onload="
+        document.documentElement.pauseAnimations();
+        document.documentElement.setCurrentTime(0);
+        document.getElementById('a').beginElementAt(1);
+        document.documentElement.setCurrentTime(2)">
+  <!--
+    This test case sets up a cycle between simultaneous instance times such that
+    when the instance times are sorted if this cycle is not detected we will
+    crash.
+  -->
+  <rect width="100" height="100" fill="red">
+    <set attributeName="fill" to="blue" begin="a.begin" dur="4s"/>
+    <set attributeName="fill" to="green" id="a"
+      begin="b.begin; 3s" dur="4s"/>
+    <set attributeName="fill" to="red" id="b"
+      begin="a.begin" dur="4s"/>
+  </rect>
+</svg>
diff --git a/dom/smil/crashtests/555026-1.svg b/dom/smil/crashtests/555026-1.svg
new file mode 100644
index 0000000000..76b4cf0756
--- /dev/null
+++ b/dom/smil/crashtests/555026-1.svg
@@ -0,0 +1,25 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg"
+     class="reftest-wait"
+     onload="go()">
+  <script>
+    function go() {
+      // setCurrentTime to force a sample
+      document.documentElement.setCurrentTime(1);
+      document.documentElement.removeAttribute("class");
+    }
+  </script>
+  <rect id="myRect" fill="blue" height="40" width="40">
+    <!-- The "keyTimes" values below are invalid, but they should be ignored
+         (and definitely shouldn't trigger any assertion failures) since we're
+         in paced calcMode. -->
+    <animate attributeName="x" by="50" calcMode="paced" dur="2s"
+             keyTimes="0; -1"/>
+    <animate attributeName="x" by="50" calcMode="paced" dur="2s"
+             keyTimes=""/>
+    <animate attributeName="x" by="50" calcMode="paced" dur="2s"
+             keyTimes="abc"/>
+    <animate attributeName="x" by="50" calcMode="paced" dur="2s"
+             keyTimes="5"/>
+  </rect>
+</svg>
diff --git a/dom/smil/crashtests/556841-1.svg b/dom/smil/crashtests/556841-1.svg
new file mode 100644
index 0000000000..92712deaa9
--- /dev/null
+++ b/dom/smil/crashtests/556841-1.svg
@@ -0,0 +1,16 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg"
+     class="reftest-wait"
+     onload="go()">
+  <script>
+    function go() {
+      // setCurrentTime to force a sample
+      document.documentElement.setCurrentTime(2);
+      document.documentElement.removeAttribute("class");
+    }
+  </script>
+  <rect fill="teal" x="50" y="50" width="20" height="20">
+    <animateTransform attributeName="transform" type="rotate" by="30"
+                      calcMode="paced" dur="4s"/>
+  </rect>
+</svg>
diff --git a/dom/smil/crashtests/572938-1.svg b/dom/smil/crashtests/572938-1.svg
new file mode 100644
index 0000000000..d759944c7d
--- /dev/null
+++ b/dom/smil/crashtests/572938-1.svg
@@ -0,0 +1,12 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+  xmlns:xlink="http://www.w3.org/1999/xlink">
+  <defs>
+    <text id="myText">Used Text Element
+      <set attributeName="display" to="none"/>
+    </text>
+  </defs>
+  <use xlink:href="#myText" x="20" y="40"/>
+  <text x="20" y="60">Normal Text Element
+    <set attributeName="display" to="none"/>
+  </text>
+</svg>
diff --git a/dom/smil/crashtests/572938-2.svg b/dom/smil/crashtests/572938-2.svg
new file mode 100644
index 0000000000..8b9cf7b70e
--- /dev/null
+++ b/dom/smil/crashtests/572938-2.svg
@@ -0,0 +1,22 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+  xmlns:xlink="http://www.w3.org/1999/xlink"
+  class="reftest-wait">
+
+    <script>
+    function boom()
+    {
+      document.getElementById("circleID").removeChild(
+        document.getElementById("at"));
+      document.documentElement.removeAttribute("class");
+    }
+    window.addEventListener("load", boom, false);
+    </script>
+
+    <circle id="circleID">
+        <animate/>
+        <animateTransform id="at" attributeName="transform"/>
+    </circle>
+    <animate attributeName="stroke-width"/>
+    <use xlink:href="#circleID"/>
+
+</svg>
diff --git a/dom/smil/crashtests/572938-3.svg b/dom/smil/crashtests/572938-3.svg
new file mode 100644
index 0000000000..642ad32fba
--- /dev/null
+++ b/dom/smil/crashtests/572938-3.svg
@@ -0,0 +1,10 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+  xmlns:xlink="http://www.w3.org/1999/xlink">
+  <defs>
+    <text id="a">Text A</text>
+    <text id="b">Text B</text>
+  </defs>
+  <use xlink:href="#a" x="20" y="40">
+    <set attributeName="xlink:href" to="#b" dur="2s"/>
+  </use>
+</svg>
diff --git a/dom/smil/crashtests/572938-4.svg b/dom/smil/crashtests/572938-4.svg
new file mode 100644
index 0000000000..549d43dd62
--- /dev/null
+++ b/dom/smil/crashtests/572938-4.svg
@@ -0,0 +1,10 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+   xmlns:xlink="http://www.w3.org/1999/xlink">
+<g id="a">
+ <path d=""><animate/></path>
+</g>
+<g display="none">
+<use xlink:href="#a" x="80"/>
+<set attributeName="display" to="inline"/>
+</g>
+</svg>
diff --git a/dom/smil/crashtests/588287-1.svg b/dom/smil/crashtests/588287-1.svg
new file mode 100644
index 0000000000..cc35cf6b46
--- /dev/null
+++ b/dom/smil/crashtests/588287-1.svg
@@ -0,0 +1,24 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+<script>
+
+function boom()
+{
+  var animate = document.createElementNS("http://www.w3.org/2000/svg", "animate");
+  animate.setAttributeNS(null, "begin", "0.5s");
+  document.documentElement.appendChild(animate);
+  
+  setTimeout(function() {
+    var g = document.createElement("g");
+    var svg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
+    g.appendChild(svg);
+    document.documentElement.appendChild(g);
+    svg.appendChild(animate);
+    document.documentElement.removeAttribute("class");
+  }, 400);
+}
+
+window.addEventListener("load", function() { setTimeout(boom, 200) }, false);
+
+</script>
+</svg>
diff --git a/dom/smil/crashtests/588287-2.svg b/dom/smil/crashtests/588287-2.svg
new file mode 100644
index 0000000000..70d8e76391
--- /dev/null
+++ b/dom/smil/crashtests/588287-2.svg
@@ -0,0 +1,26 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+<script>
+
+function boom()
+{
+  var animate = document.createElementNS("http://www.w3.org/2000/svg", "animate");
+  animate.setAttributeNS(null, "begin", "0.5s");
+  document.documentElement.appendChild(animate);
+  
+  setTimeout(function() {
+    var g = document.createElement("g");
+    var svg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
+    g.appendChild(svg);
+    document.documentElement.appendChild(g);
+    svg.setCurrentTime(0.2);
+    svg.appendChild(animate);
+    svg.setCurrentTime(0.0); // Trigger backwards seek
+    document.documentElement.removeAttribute("class");
+  }, 400);
+}
+
+window.addEventListener("load", function() { setTimeout(boom, 200) }, false);
+
+</script>
+</svg>
diff --git a/dom/smil/crashtests/590425-1.html b/dom/smil/crashtests/590425-1.html
new file mode 100644
index 0000000000..906d348db2
--- /dev/null
+++ b/dom/smil/crashtests/590425-1.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<html class="reftest-wait">
+<head>
+<script>
+
+function boom()
+{
+  var frame = document.getElementById("frame")
+  var frameSVG = frame.contentDocument.getElementById('s');
+  var animate = frame.contentDocument.createElementNS("http://www.w3.org/2000/svg", "animate");
+  frame.remove();
+  frameSVG.appendChild(animate);
+  document.documentElement.removeAttribute("class");
+}
+
+</script>
+</head>
+
+<body onload="boom()">
+
+<iframe id="frame" srcdoc="<body><svg id=s>"></iframe>
+
+</body>
+</html>
diff --git a/dom/smil/crashtests/594653-1.svg b/dom/smil/crashtests/594653-1.svg
new file mode 100644
index 0000000000..76352ce30b
--- /dev/null
+++ b/dom/smil/crashtests/594653-1.svg
@@ -0,0 +1,26 @@
+<?xml version="1.0"?>
+
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+<script>
+<![CDATA[
+
+window.addEventListener("load", boom, false);
+
+function boom()
+{
+  setTimeout(bang, 0);
+}
+
+function bang()
+{
+  document.documentElement.setCurrentTime(0);
+  document.documentElement.removeAttribute("class");
+}
+
+]]>
+</script>
+
+<animate id="b"/>
+<animate end="b.end"/>
+
+</svg>
diff --git a/dom/smil/crashtests/596796-1.svg b/dom/smil/crashtests/596796-1.svg
new file mode 100644
index 0000000000..52a66fd582
--- /dev/null
+++ b/dom/smil/crashtests/596796-1.svg
@@ -0,0 +1,15 @@
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+
+<script>
+function boom()
+{
+  document.documentElement.appendChild(document.getElementById("a"));
+  document.documentElement.removeAttribute("class");
+}
+
+window.addEventListener("load", boom, false);
+</script>
+
+<animate end="a.begin" id="a"/>
+
+</svg>
diff --git a/dom/smil/crashtests/605345-1.svg b/dom/smil/crashtests/605345-1.svg
new file mode 100644
index 0000000000..94887cf713
--- /dev/null
+++ b/dom/smil/crashtests/605345-1.svg
@@ -0,0 +1,25 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+<script>
+<![CDATA[
+
+function boom()
+{
+  var anim = document.getElementById("a");
+  var newSvg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
+  var oldSvg = document.removeChild(document.documentElement);
+  document.appendChild(newSvg);
+  document.removeChild(document.documentElement);
+  newSvg.pauseAnimations();
+  document.appendChild(newSvg);
+  newSvg.appendChild(anim);
+
+  oldSvg.removeAttribute("class");
+}
+
+window.addEventListener("load", function() { setTimeout(boom, 200); }, false);
+
+]]>
+</script>
+<animate id="a"/>
+</svg>
diff --git a/dom/smil/crashtests/606101-1.svg b/dom/smil/crashtests/606101-1.svg
new file mode 100644
index 0000000000..988c86fa33
--- /dev/null
+++ b/dom/smil/crashtests/606101-1.svg
@@ -0,0 +1,23 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+     class="reftest-wait">
+<script>
+
+function boom()
+{
+  var origSVG = document.documentElement;
+
+  var a = document.createElementNS("http://www.w3.org/2000/svg", "animate");
+  var g = document.createElementNS("http://www.w3.org/2000/svg", "g");
+  var s = document.createElementNS("http://www.w3.org/2000/svg", "svg");
+  document.removeChild(document.documentElement);
+  document.appendChild(g);
+  s.appendChild(a);
+  g.appendChild(s);
+
+  origSVG.removeAttribute("class");
+}
+
+window.addEventListener("load", boom, false);
+
+</script>
+</svg>
diff --git a/dom/smil/crashtests/608295-1.html b/dom/smil/crashtests/608295-1.html
new file mode 100644
index 0000000000..354e6f9099
--- /dev/null
+++ b/dom/smil/crashtests/608295-1.html
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<html class="reftest-wait">
+<head>
+<script>
+
+function boom()
+{
+  // NB: <script src> is needed to trigger the bug. I'm being clever by also using it to remove reftest-wait.
+  var s = "<script src='data:text/javascript,parent.document.documentElement.className=null;'><\/script><svg>";
+  document.getElementById("f").contentDocument.write(s);
+}
+
+</script>
+</head>
+<body onload="boom();">
+<iframe id="f"></iframe>
+</body>
+</html>
diff --git a/dom/smil/crashtests/608549-1.svg b/dom/smil/crashtests/608549-1.svg
new file mode 100644
index 0000000000..dd441e0135
--- /dev/null
+++ b/dom/smil/crashtests/608549-1.svg
@@ -0,0 +1,29 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+<script>
+<![CDATA[
+
+function boom()
+{
+  try {
+    document.getElementById("set").beginElementAt(NaN);
+    return;
+  } catch (e) {}
+  try {
+    document.getElementById("set").endElementAt(NaN);
+    return;
+  } catch (e) {}
+
+  // If we got here we threw both exceptions and skipped both early-returns, as
+  // expected.
+  document.documentElement.removeAttribute("class");
+}
+
+window.addEventListener("load", boom, false);
+
+]]>
+</script>
+
+<set id="set" attributeName="fill" to="green" begin="indefinite"/>
+
+</svg>
diff --git a/dom/smil/crashtests/611927-1.svg b/dom/smil/crashtests/611927-1.svg
new file mode 100644
index 0000000000..ea60f4ce1c
--- /dev/null
+++ b/dom/smil/crashtests/611927-1.svg
@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+  <animate attributeName="stroke-width"/>
+  <animate attributeName="stroke-width" by="10em"/>
+</svg>
diff --git a/dom/smil/crashtests/615002-1.svg b/dom/smil/crashtests/615002-1.svg
new file mode 100644
index 0000000000..eb9a293199
--- /dev/null
+++ b/dom/smil/crashtests/615002-1.svg
@@ -0,0 +1,16 @@
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+<script>
+function boom()
+{
+  var a = document.getElementById("a");
+  a.removeAttribute('dur');
+  document.documentElement.appendChild(a);
+  // Force a sample
+  document.documentElement.setCurrentTime(0);
+  document.documentElement.removeAttribute("class");
+}
+
+window.addEventListener("load", boom, false);
+</script>
+<animate begin="-2s" dur="2s" id="a"/>
+</svg>
diff --git a/dom/smil/crashtests/615872-1.svg b/dom/smil/crashtests/615872-1.svg
new file mode 100644
index 0000000000..e0cdf21546
--- /dev/null
+++ b/dom/smil/crashtests/615872-1.svg
@@ -0,0 +1,21 @@
+<?xml version="1.0"?>
+
+<svg xmlns="http://www.w3.org/2000/svg"><script>
+<![CDATA[
+
+function boom()
+{
+  var r = document.documentElement;
+  var s = document.createElementNS("http://www.w3.org/2000/svg", "set");
+  s.setAttributeNS(null, "begin", "1s");
+  r.appendChild(s);
+  r.setCurrentTime(2);
+  document.removeChild(r);
+  r.setCurrentTime(0);
+  s.beginElementAt(0);
+}
+
+window.addEventListener("load", boom, false);
+
+]]>
+</script></svg>
diff --git a/dom/smil/crashtests/641388-1.html b/dom/smil/crashtests/641388-1.html
new file mode 100644
index 0000000000..25c941dedb
--- /dev/null
+++ b/dom/smil/crashtests/641388-1.html
@@ -0,0 +1,97 @@
+<script>

+

+var ar = new Array(100000);

+

+function fill() {

+        var s = unescape("%ubeef%udead%udead%udead%u0000%u0000%u3030%u3030");

+        while(s.length < 0x40000) {

+                for(var x=0; x<100; x++) ar.push(s+s);

+                s+=s;

+        }

+}

+

+

+function gc() {

+                var evt = document.createEvent("Events");

+                evt.initEvent("please-gc", true, false);

+                document.dispatchEvent(evt);

+		fill();

+}

+

+

+gc();

+function start(){

+tmp = document.createElement('iframe');

+tmp.src="data:image/svg+xml,"+escape("<?xml version='1.0' standalone='no'?><!DOCTYPE svg><svg xmlns='http://www.w3.org/2000/svg'><defs id='element1'></defs><g id='element5'></g></svg>");

+tmp.id = 'ifr23282';

+try{document.getElementById('store_div').appendChild(tmp);}catch(e){}

+window.setTimeout('startrly()', 100);

+} function startrly() {

+try{o6=document.createComment(null);}catch(e){}

+try{o9=document.getElementById('ifr23282').contentDocument.documentElement;;}catch(e){}

+try{o13=document.getElementById('ifr23282').contentDocument.getElementById('element1');;}catch(e){}

+try{o15=document.getElementById('ifr23282').contentDocument.getElementById('element5');;}catch(e){}

+try{tmp = document.createElement('iframe');}catch(e){}

+try{tmp.id = 'ifr6690';}catch(e){}

+try{o6.ownerDocument.documentElement.appendChild(tmp);}catch(e){}

+window.setTimeout('start_dataiframe0()',100);

+} function start_dataiframe0(){

+try{o19=o6.ownerDocument.getElementById('ifr6690').contentDocument.documentElement;;}catch(e){}

+try{o24=document.createElementNS('http://www.w3.org/1998/Math/MathML','annotation-xml');;}catch(e){}

+try{o35=document.createElementNS('http://www.w3.org/1998/Math/MathML','emptyset');;}catch(e){}

+try{o40=o19.cloneNode(false);;}catch(e){}

+try{o19.appendChild(o13);}catch(e){}

+try{o19.appendChild(o15);}catch(e){}

+try{o24.appendChild(o40);}catch(e){}

+try{tmp = document.createElement('iframe');}catch(e){}

+tmp.src="data:text/html,<article%20id='element1'></article><command%20id='element3'></command>";

+try{tmp.id = 'ifr17516';}catch(e){}

+try{o13.ownerDocument.documentElement.appendChild(tmp);}catch(e){}

+window.setTimeout('start_dataiframe4()',100);

+} function start_dataiframe4(){

+try{o62=o13.ownerDocument.getElementById('ifr17516').contentDocument.getElementById('element1');;}catch(e){}

+try{tmp.id = 'ifr2522';}catch(e){}

+try{o101=o15.ownerDocument.getElementById('ifr2522').contentDocument.getElementById('element3');;}catch(e){}

+try{o101.appendChild(o24);}catch(e){}

+try{o112=document.createElementNS('http://www.w3.org/1999/xhtml', 'script');;}catch(e){}

+try{o124=document.createElementNS('http://www.w3.org/1998/Math/MathML','root');;}catch(e){}

+try{o125=document.createElementNS('http://www.w3.org/2000/svg','font-face');;}catch(e){}

+gc()

+try{o150=o40;}catch(e){}

+try{tmp.id = 'ifr44501';}catch(e){}

+try{o124.ownerDocument.documentElement.appendChild(tmp);}catch(e){}

+window.setTimeout('start_dataiframe7()',100);

+} function start_dataiframe7(){

+try{o152=o124.ownerDocument.getElementById('ifr44501').contentDocument.documentElement;;}catch(e){}

+try{tmp = document.createElement('iframe');}catch(e){}

+try{tmp.src="data:text/html,<div%20id='element1'></div>";}catch(e){}

+try{tmp.id = 'ifr55543';}catch(e){}

+try{o125.ownerDocument.documentElement.appendChild(tmp);}catch(e){}

+window.setTimeout('start_dataiframe10()',100);

+} function start_dataiframe10(){

+try{o198=o125.ownerDocument.getElementById('ifr55543').contentDocument.getElementById('element1');;}catch(e){}

+try{o152.appendChild(o101);}catch(e){}

+try{o152.ownerDocument.documentElement.appendChild(tmp);}catch(e){}

+window.setTimeout('start_dataiframe17()',100);

+} function start_dataiframe17(){

+try{o286=o152.ownerDocument.getElementById('ifr55543').contentDocument.documentElement;;}catch(e){}

+try{o288=o152.ownerDocument.getElementById('ifr55543').contentDocument.getElementById('element1');;}catch(e){}

+try{o349=document.createElementNS('http://www.w3.org/2000/svg','animate');;}catch(e){}

+try{o150.appendChild(o349);}catch(e){}

+try{o288.appendChild(o150);}catch(e){}

+try{o198.appendChild(o349);}catch(e){}

+window.setTimeout('start_dataiframe24()',100);

+} function start_dataiframe24(){ 

+try{o286.appendChild(o9);}catch(e){}

+try{o62.appendChild(o152);}catch(e){}

+try{o112.appendChild(o286);}catch(e){}

+try{o534=o35.cloneNode(false);;}catch(e){}

+gc();

+o35 = null;

+gc();

+window.setTimeout("fill()",300);

+}

+</script>

+<body onload="start()">

+<div id="store_div"></div>

+</body>

diff --git a/dom/smil/crashtests/641388-2.html b/dom/smil/crashtests/641388-2.html
new file mode 100644
index 0000000000..f2ddead7e1
--- /dev/null
+++ b/dom/smil/crashtests/641388-2.html
@@ -0,0 +1,79 @@
+<script>

+function gc() {

+                var evt = document.createEvent("Events");

+                evt.initEvent("please-gc", true, false);

+                document.dispatchEvent(evt);

+        }

+var ar =new Array(100000);

+function fill() {

+        var s = unescape("%u0000%u0000%u3030%u3030");

+        while(s.length < 0x40000) {

+                for(var x=0; x<100; x++) ar.push(s+s);

+                s+=s;

+        }

+}

+

+

+function start(){

+tmp = document.createElement('iframe'); 'ifr16727';

+document.documentElement.appendChild(tmp);

+window.setTimeout('start_dataiframe0()',100);

+} function start_dataiframe0(){

+o20=document.createElement('iframe');

+tmp.id = 'ifr4446';;

+o68=o20;

+o101=document.getElementById('ifr4446').contentDocument.createElement('thead');;

+tmp.src="data:text/html," + escape("<html id='element0'><noscript id='element1'></html>");

+tmp.id = 'ifr49879';

+window.setTimeout('start_dataiframe6()',100);

+} function start_dataiframe6(){

+o104=document.getElementById('ifr49879').contentDocument.getElementById('element0');;

+o105=document.getElementById('ifr49879').contentDocument.getElementById('element1');;

+o120=document.getElementById('ifr49879').contentDocument.createElement('figure');;

+o105.appendChild(o120);

+o122=o105.lastElementChild;

+o140=document.getElementById('ifr49879').contentDocument.createElement('style');;

+o141=document.getElementById('ifr49879').contentDocument.createElementNS('http://www.w3.org/2000/svg','animate');;

+o151=o141.cloneNode(true);;

+tmp = document.createElement('iframe');

+tmp.src='data:text/html,%3Cform%20style%3B%27%20id%3D%27element3%27%3E%20%3Caside%20style%20id%3D%27element4%27%%3E';

+tmp.id = 'ifr13645';

+document.documentElement.appendChild(tmp);

+window.setTimeout('start_dataiframe8()',100);

+} function start_dataiframe8(){

+o154=document.getElementById('ifr13645').contentDocument.documentElement;;

+o158=document.getElementById('ifr13645').contentDocument.getElementById('element3');;

+o159=document.getElementById('ifr13645').contentDocument.getElementById('element4');;

+tmp.id = 'ifr17164';

+o120.ownerDocument.documentElement.appendChild(tmp);

+o171=o120.ownerDocument.getElementById('ifr17164').contentDocument.documentElement;;

+tmp = o158.ownerDocument.createElement('iframe');

+o101.appendChild(o151);

+o122.appendChild(o154);

+o68.appendChild(o171);

+o179=document.createElement('tbody');;

+o154.addEventListener('DOMNodeRemoved',function (event) { gc(); });

+tmp.src='data:text/html,%3Cs%27%20id%3D%27element0%27element4%27%3E%3Cs%20id%3D%27element5%27%20style%3D%27text-indent%3A%20-1%25%3Bmin-w%2C%20rgba%28255%2C0%2C0%2C0%29%20strict%3Bcolumn-count7element9%27%3E%s%3E';

+tmp.id = 'ifr35960';

+o154.ownerDocument.documentElement.appendChild(tmp);

+window.setTimeout('start_dataiframe13()',100);

+} function start_dataiframe13(){

+o217=o154.ownerDocument.getElementById('ifr35960').contentDocument.documentElement;;

+o218=o154.ownerDocument.getElementById('ifr35960').contentDocument.getElementById('element0');;

+o223=o154.ownerDocument.getElementById('ifr35960').contentDocument.getElementById('element5');;

+o223.appendChild(o101);

+o218.appendChild(o140);

+o140.appendChild(o151);

+o104.appendChild(o179);

+o230=o120.ownerDocument.getElementById('ifr17164').contentDocument.createElementNS('http://www.w3.org/2000/svg','svg');;

+window.setTimeout('start_dataiframe14()',100);

+} function start_dataiframe14(){

+gc();fill();

+o140.appendChild(o230);

+o171.appendChild(o104);

+o159.appendChild(o217);

+o158.appendChild(o218);

+}

+window.setTimeout("start()",100);

+</script>

+

diff --git a/dom/smil/crashtests/650732-1.svg b/dom/smil/crashtests/650732-1.svg
new file mode 100644
index 0000000000..95be31c16a
--- /dev/null
+++ b/dom/smil/crashtests/650732-1.svg
@@ -0,0 +1,46 @@
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+  <rect fill="green" width="100" height="100">
+    <set id="a" attributeName="fill" to="blue"
+      begin="6s" end="986s"/>
+    <set id="b" attributeName="fill" to="orange"
+      begin="a.begin+69.3s;b.begin+700s" dur="700s" end="a.end"/>
+    <set id="c" attributeName="fill" to="yellow"
+      begin="0s;b.begin+700s"/>
+  </rect>
+  <script type="text/javascript">
+<![CDATA[
+const max_attempts = 100;
+var   attempts = 0;
+function attemptCrash()
+{
+  remove();
+  add();
+  if (++attempts >= max_attempts) {
+    document.documentElement.removeAttribute("class");
+  } else {
+    setTimeout(attemptCrash, 0);
+  }
+}
+function add()
+{
+  const svgns = "http://www.w3.org/2000/svg";
+  var elem = document.createElementNS(svgns, "set");
+  elem.setAttribute("id", "b");
+  elem.setAttribute("attributeName", "fill");
+  elem.setAttribute("to", "orange");
+  elem.setAttribute("begin", "a.begin+69.3s;b.begin+700s");
+  elem.setAttribute("dur", "700s");
+  elem.setAttribute("end", "a.end");
+  rect = document.getElementsByTagNameNS(svgns, "rect")[0];
+  rect.appendChild(elem);
+}
+function remove()
+{
+  var elem = document.getElementById('b');
+  elem.parentNode.removeChild(elem);
+  elem = null;
+}
+window.addEventListener("load", attemptCrash, false);
+]]>
+ </script>
+</svg>
diff --git a/dom/smil/crashtests/665334-1.svg b/dom/smil/crashtests/665334-1.svg
new file mode 100644
index 0000000000..94916d1e0e
--- /dev/null
+++ b/dom/smil/crashtests/665334-1.svg
@@ -0,0 +1,13 @@
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+<script>
+function boom()
+{
+  // Remove the first 'a'.
+  document.documentElement.removeChild(document.getElementById("a"));
+  document.documentElement.removeAttribute("class");
+}
+window.addEventListener("load", boom, false);
+</script>
+<animate id="a"/>
+<animate id="a" end="a.begin" />
+</svg>
diff --git a/dom/smil/crashtests/669225-1.svg b/dom/smil/crashtests/669225-1.svg
new file mode 100644
index 0000000000..9660105631
--- /dev/null
+++ b/dom/smil/crashtests/669225-1.svg
@@ -0,0 +1,21 @@
+<?xml version="1.0"?>
+
+<svg xmlns="http://www.w3.org/2000/svg">
+
+<script type="text/javascript">
+<![CDATA[
+
+function boom()
+{
+  document.documentElement.appendChild(document.getElementById("a"));
+}
+
+window.addEventListener("load", boom, false);
+
+]]>
+</script>
+
+<animate end="a.begin" id="a"/>
+<animate end="a.begin" id="a"/>
+
+</svg>
diff --git a/dom/smil/crashtests/669225-2.svg b/dom/smil/crashtests/669225-2.svg
new file mode 100644
index 0000000000..00d52c1f4c
--- /dev/null
+++ b/dom/smil/crashtests/669225-2.svg
@@ -0,0 +1,21 @@
+<?xml version="1.0"?>
+
+<svg xmlns="http://www.w3.org/2000/svg">
+
+<script type="text/javascript">
+<![CDATA[
+
+function boom()
+{
+  var a = document.getElementById("a");
+  a.removeAttribute("end");
+  a.setAttribute("end", "a.begin");
+}
+
+window.addEventListener("load", boom, false);
+
+]]>
+</script>
+
+<animate end="0" id="a" onend="boom()"/>
+</svg>
diff --git a/dom/smil/crashtests/670313-1.svg b/dom/smil/crashtests/670313-1.svg
new file mode 100644
index 0000000000..97e12f35ac
--- /dev/null
+++ b/dom/smil/crashtests/670313-1.svg
@@ -0,0 +1,20 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg"
+     class="reftest-wait">
+<script type="text/javascript">
+<![CDATA[
+
+function boom()
+{
+  try {
+    document.getElementById("x").beginElementAt(36028797018963970);
+  } catch (e) { }
+  document.documentElement.removeAttribute("class");
+}
+
+window.addEventListener("load", boom, false);
+
+]]>
+</script>
+<animate id="x" begin="a" />
+</svg>
diff --git a/dom/smil/crashtests/678822-1.svg b/dom/smil/crashtests/678822-1.svg
new file mode 100644
index 0000000000..a5e81ee10f
--- /dev/null
+++ b/dom/smil/crashtests/678822-1.svg
@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+  <animate repeatCount="2" dur="1s" accumulate="1" />
+</svg>
diff --git a/dom/smil/crashtests/678847-1.svg b/dom/smil/crashtests/678847-1.svg
new file mode 100644
index 0000000000..1fa2718cbb
--- /dev/null
+++ b/dom/smil/crashtests/678847-1.svg
@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+<animate id="a" end="a.end+6s" />
+</svg>
diff --git a/dom/smil/crashtests/678938-1.svg b/dom/smil/crashtests/678938-1.svg
new file mode 100644
index 0000000000..f3f8308fa5
--- /dev/null
+++ b/dom/smil/crashtests/678938-1.svg
@@ -0,0 +1,11 @@
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+<script>
+  window.addEventListener("load", function() {
+    setTimeout(function() {
+      document.documentElement.setCurrentTime(0);
+      document.documentElement.removeAttribute("class");
+    }, 0);
+  }, false);
+</script>
+<set id="c"/><set id="b" begin="c.begin; b.begin"/>
+</svg>
diff --git a/dom/smil/crashtests/690994-1.svg b/dom/smil/crashtests/690994-1.svg
new file mode 100644
index 0000000000..252fd2c264
--- /dev/null
+++ b/dom/smil/crashtests/690994-1.svg
@@ -0,0 +1,17 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" class="reftest-wait" onload="go()">
+<script>
+<![CDATA[
+function go() {
+  document.documentElement.setCurrentTime(100);
+}
+function boom()
+{
+  document.documentElement.removeChild(document.getElementById("a"));
+  document.documentElement.removeAttribute("class");
+}
+]]>
+</script>
+<animate id="a" begin="a.end; 99.9s" end="a.begin+0.2s" onend="boom()"/>
+<animate id="a" begin="a.end; 99.9s" end="a.begin+0.2s"/>
+</svg>
diff --git a/dom/smil/crashtests/691337-1.svg b/dom/smil/crashtests/691337-1.svg
new file mode 100644
index 0000000000..c341faa6b2
--- /dev/null
+++ b/dom/smil/crashtests/691337-1.svg
@@ -0,0 +1,8 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
+  <rect width="100" height="100" fill="blue">
+    <animate attributeName="fill"
+      begin="999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+      dur="5s" from="blue" to="red" repeatCount="indefinite" additive="sum"/>
+  </rect>
+</svg>
diff --git a/dom/smil/crashtests/691337-2.svg b/dom/smil/crashtests/691337-2.svg
new file mode 100644
index 0000000000..f4408ae5ee
--- /dev/null
+++ b/dom/smil/crashtests/691337-2.svg
@@ -0,0 +1,11 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
+  <rect width="100" height="100" fill="blue">
+    <animate attributeName="fill" id="a"
+      begin="4999999999999999" dur="5s" from="blue" to="red"
+      repeatCount="indefinite" additive="sum"/>
+    <animate attributeName="fill"
+      begin="a.begin+4999999999999999"
+      dur="5s" from="blue" to="red" repeatCount="indefinite" additive="sum"/>
+  </rect>
+</svg>
diff --git a/dom/smil/crashtests/697640-1.svg b/dom/smil/crashtests/697640-1.svg
new file mode 100644
index 0000000000..c2e1b89fdb
--- /dev/null
+++ b/dom/smil/crashtests/697640-1.svg
@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+  <animate id="b" end="b.end" dur="3s" />
+</svg>
diff --git a/dom/smil/crashtests/699325-1.svg b/dom/smil/crashtests/699325-1.svg
new file mode 100644
index 0000000000..7496c6ae21
--- /dev/null
+++ b/dom/smil/crashtests/699325-1.svg
@@ -0,0 +1,5 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+  <rect fill="blue" height="100" width="100">
+    <animate id="a" attributeName="x"  calcMode="paced" values="50; 50; 50"/>
+  </rect>
+</svg>
diff --git a/dom/smil/crashtests/709907-1.svg b/dom/smil/crashtests/709907-1.svg
new file mode 100644
index 0000000000..631911970c
--- /dev/null
+++ b/dom/smil/crashtests/709907-1.svg
@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+  <animate attributeName="stroke-dasharray" from="-3" />
+</svg>
diff --git a/dom/smil/crashtests/720103-1.svg b/dom/smil/crashtests/720103-1.svg
new file mode 100644
index 0000000000..a51a3bf0fc
--- /dev/null
+++ b/dom/smil/crashtests/720103-1.svg
@@ -0,0 +1,4 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg">
+<animate id="a" begin="-3.1s" end="a.begin+0.2s"/>
+</svg>
diff --git a/dom/smil/crashtests/849593-1.xhtml b/dom/smil/crashtests/849593-1.xhtml
new file mode 100644
index 0000000000..95b9b2feb8
--- /dev/null
+++ b/dom/smil/crashtests/849593-1.xhtml
@@ -0,0 +1,34 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head class="reftest-wait">
+<meta charset="utf-8"/>
+<script>
+<![CDATA[
+
+function boom()
+{
+  var a = document.getElementById('a');
+  var b = document.getElementById('b');
+  var c = document.getElementById('c');
+  var d = document.getElementById('d');
+
+  b.setCurrentTime(1);
+
+  a.appendChild(c);
+  document.body.removeChild(a);
+  b.appendChild(c);
+  document.documentElement.offsetHeight;
+  d.appendChild(a);
+
+  document.documentElement.removeAttribute('class');
+}
+
+]]>
+</script>
+</head>
+
+<body onload="setTimeout(boom, 0);">
+<svg xmlns="http://www.w3.org/2000/svg" id="a"/>
+<svg xmlns="http://www.w3.org/2000/svg" id="b"/>
+<set xmlns="http://www.w3.org/2000/svg" begin="1s" id="c"><div xmlns="http://www.w3.org/1999/xhtml" id="d"></div></set>
+</body>
+</html>
diff --git a/dom/smil/crashtests/crashtests.list b/dom/smil/crashtests/crashtests.list
new file mode 100644
index 0000000000..1ca739c9ae
--- /dev/null
+++ b/dom/smil/crashtests/crashtests.list
@@ -0,0 +1,62 @@
+load 483584-1.svg
+load 483584-2.svg
+load 523188-1.svg
+load 525099-1.svg
+load 526536-1.svg
+load 526875-1.svg
+load 526875-2.svg
+load 529387-1.xhtml
+load 531550-1.svg
+load 541297-1.svg
+load 547333-1.svg
+load 548899-1.svg
+load 551620-1.svg
+load 554141-1.svg
+load 554202-2.svg
+load 555026-1.svg
+load 556841-1.svg
+load 572938-1.svg
+load 572938-2.svg
+load 572938-3.svg
+load 572938-4.svg
+load 588287-1.svg
+load 588287-2.svg
+load 590425-1.html
+load 594653-1.svg
+load 596796-1.svg
+load 605345-1.svg
+load 606101-1.svg
+load 608295-1.html
+load 608549-1.svg
+load 611927-1.svg
+load 615002-1.svg
+load 615872-1.svg
+load 641388-1.html
+load 641388-2.html
+load 650732-1.svg
+load 665334-1.svg
+load 669225-1.svg
+load 669225-2.svg
+load 670313-1.svg
+load 678822-1.svg
+load 678847-1.svg
+load 678938-1.svg
+load 690994-1.svg
+load 691337-1.svg
+load 691337-2.svg
+load 697640-1.svg
+load 699325-1.svg
+load 709907-1.svg
+load 720103-1.svg
+load 849593-1.xhtml
+load 1010681-1.svg
+load 1322770-1.svg
+load 1322849-1.svg
+load 1343357-1.html
+load 1375596-1.svg
+load 1402547-1.html
+load 1411963-1.html
+load 1413319-1.html
+load 1535388-1.html
+load 1772573-1.html
+load 1780800-1.html
diff --git a/dom/smil/moz.build b/dom/smil/moz.build
new file mode 100644
index 0000000000..2280cd7aa3
--- /dev/null
+++ b/dom/smil/moz.build
@@ -0,0 +1,74 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "SVG")
+
+MOCHITEST_MANIFESTS += ["test/mochitest.toml"]
+
+EXPORTS.mozilla += [
+    "SMILAnimationController.h",
+    "SMILAnimationFunction.h",
+    "SMILAttr.h",
+    "SMILCompositorTable.h",
+    "SMILCSSValueType.h",
+    "SMILInstanceTime.h",
+    "SMILInterval.h",
+    "SMILKeySpline.h",
+    "SMILMilestone.h",
+    "SMILNullType.h",
+    "SMILParserUtils.h",
+    "SMILRepeatCount.h",
+    "SMILSetAnimationFunction.h",
+    "SMILTargetIdentifier.h",
+    "SMILTimeContainer.h",
+    "SMILTimedElement.h",
+    "SMILTimeValue.h",
+    "SMILTimeValueSpec.h",
+    "SMILTimeValueSpecParams.h",
+    "SMILType.h",
+    "SMILTypes.h",
+    "SMILValue.h",
+]
+
+EXPORTS.mozilla.dom += [
+    "TimeEvent.h",
+]
+
+UNIFIED_SOURCES += [
+    "SMILAnimationController.cpp",
+    "SMILAnimationFunction.cpp",
+    "SMILBoolType.cpp",
+    "SMILCompositor.cpp",
+    "SMILCSSProperty.cpp",
+    "SMILCSSValueType.cpp",
+    "SMILEnumType.cpp",
+    "SMILFloatType.cpp",
+    "SMILInstanceTime.cpp",
+    "SMILIntegerType.cpp",
+    "SMILInterval.cpp",
+    "SMILKeySpline.cpp",
+    "SMILNullType.cpp",
+    "SMILParserUtils.cpp",
+    "SMILRepeatCount.cpp",
+    "SMILSetAnimationFunction.cpp",
+    "SMILStringType.cpp",
+    "SMILTimeContainer.cpp",
+    "SMILTimedElement.cpp",
+    "SMILTimeValue.cpp",
+    "SMILTimeValueSpec.cpp",
+    "SMILValue.cpp",
+    "TimeEvent.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "/dom/base",
+    "/dom/svg",
+    "/layout/base",
+    "/layout/style",
+]
+
+FINAL_LIBRARY = "xul"
diff --git a/dom/smil/test/db_smilAnimateMotion.js b/dom/smil/test/db_smilAnimateMotion.js
new file mode 100644
index 0000000000..31c338586f
--- /dev/null
+++ b/dom/smil/test/db_smilAnimateMotion.js
@@ -0,0 +1,309 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 sw=2 sts=2 et: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* testcase data for <animateMotion> */
+
+// Fake motion 'attribute', to satisfy testing code that expects an attribute.
+var gMotionAttr = new AdditiveAttribute(
+  SMILUtil.getMotionFakeAttributeName(),
+  "XML",
+  "rect"
+);
+
+// CTM-summary-definitions, for re-use by multiple testcase bundles below.
+var _reusedCTMLists = {
+  pacedBasic: {
+    ctm0: [100, 200, 0],
+    ctm1_6: [105, 205, 0],
+    ctm1_3: [110, 210, 0],
+    ctm2_3: [120, 220, 0],
+    ctm1: [130, 210, 0],
+  },
+  pacedR60: {
+    ctm0: [100, 200, Math.PI / 3],
+    ctm1_6: [105, 205, Math.PI / 3],
+    ctm1_3: [110, 210, Math.PI / 3],
+    ctm2_3: [120, 220, Math.PI / 3],
+    ctm1: [130, 210, Math.PI / 3],
+  },
+  pacedRAuto: {
+    ctm0: [100, 200, Math.PI / 4],
+    ctm1_6: [105, 205, Math.PI / 4],
+    ctm1_3: [110, 210, Math.PI / 4],
+    ctm2_3: [120, 220, -Math.PI / 4],
+    ctm1: [130, 210, -Math.PI / 4],
+  },
+  pacedRAutoReverse: {
+    ctm0: [100, 200, (5 * Math.PI) / 4],
+    ctm1_6: [105, 205, (5 * Math.PI) / 4],
+    ctm1_3: [110, 210, (5 * Math.PI) / 4],
+    ctm2_3: [120, 220, (3 * Math.PI) / 4],
+    ctm1: [130, 210, (3 * Math.PI) / 4],
+  },
+
+  discreteBasic: {
+    ctm0: [100, 200, 0],
+    ctm1_6: [100, 200, 0],
+    ctm1_3: [120, 220, 0],
+    ctm2_3: [130, 210, 0],
+    ctm1: [130, 210, 0],
+  },
+  discreteRAuto: {
+    ctm0: [100, 200, Math.PI / 4],
+    ctm1_6: [100, 200, Math.PI / 4],
+    ctm1_3: [120, 220, -Math.PI / 4],
+    ctm2_3: [130, 210, -Math.PI / 4],
+    ctm1: [130, 210, -Math.PI / 4],
+  },
+  justMoveBasic: {
+    ctm0: [40, 80, 0],
+    ctm1_6: [40, 80, 0],
+    ctm1_3: [40, 80, 0],
+    ctm2_3: [40, 80, 0],
+    ctm1: [40, 80, 0],
+  },
+  justMoveR60: {
+    ctm0: [40, 80, Math.PI / 3],
+    ctm1_6: [40, 80, Math.PI / 3],
+    ctm1_3: [40, 80, Math.PI / 3],
+    ctm2_3: [40, 80, Math.PI / 3],
+    ctm1: [40, 80, Math.PI / 3],
+  },
+  justMoveRAuto: {
+    ctm0: [40, 80, Math.atan(2)],
+    ctm1_6: [40, 80, Math.atan(2)],
+    ctm1_3: [40, 80, Math.atan(2)],
+    ctm2_3: [40, 80, Math.atan(2)],
+    ctm1: [40, 80, Math.atan(2)],
+  },
+  justMoveRAutoReverse: {
+    ctm0: [40, 80, Math.PI + Math.atan(2)],
+    ctm1_6: [40, 80, Math.PI + Math.atan(2)],
+    ctm1_3: [40, 80, Math.PI + Math.atan(2)],
+    ctm2_3: [40, 80, Math.PI + Math.atan(2)],
+    ctm1: [40, 80, Math.PI + Math.atan(2)],
+  },
+  nullMoveBasic: {
+    ctm0: [0, 0, 0],
+    ctm1_6: [0, 0, 0],
+    ctm1_3: [0, 0, 0],
+    ctm2_3: [0, 0, 0],
+    ctm1: [0, 0, 0],
+  },
+  nullMoveRAutoReverse: {
+    ctm0: [0, 0, Math.PI],
+    ctm1_6: [0, 0, Math.PI],
+    ctm1_3: [0, 0, Math.PI],
+    ctm2_3: [0, 0, Math.PI],
+    ctm1: [0, 0, Math.PI],
+  },
+};
+
+var gMotionBundles = [
+  // Bundle to test basic functionality (using default calcMode='paced')
+  new TestcaseBundle(gMotionAttr, [
+    // Basic paced-mode (default) test, with values/mpath/path
+    new AnimMotionTestcase(
+      { values: "100, 200; 120, 220; 130, 210" },
+      _reusedCTMLists.pacedBasic
+    ),
+    new AnimMotionTestcase(
+      { path: "M100 200 L120 220 L130 210" },
+      _reusedCTMLists.pacedBasic
+    ),
+    new AnimMotionTestcase(
+      { mpath: "M100 200 L120 220 L130 210" },
+      _reusedCTMLists.pacedBasic
+    ),
+
+    // ..and now with rotate=constant value in degrees
+    new AnimMotionTestcase(
+      { values: "100,200; 120,220; 130, 210", rotate: "60" },
+      _reusedCTMLists.pacedR60
+    ),
+    new AnimMotionTestcase(
+      { path: "M100 200 L120 220 L130 210", rotate: "60" },
+      _reusedCTMLists.pacedR60
+    ),
+    new AnimMotionTestcase(
+      { mpath: "M100 200 L120 220 L130 210", rotate: "60" },
+      _reusedCTMLists.pacedR60
+    ),
+
+    // ..and now with rotate=constant value in radians
+    new AnimMotionTestcase(
+      { path: "M100 200 L120 220 L130 210", rotate: "1.0471975512rad" }, // pi/3
+      _reusedCTMLists.pacedR60
+    ),
+
+    // ..and now with rotate=auto
+    new AnimMotionTestcase(
+      { values: "100,200; 120,220; 130, 210", rotate: "auto" },
+      _reusedCTMLists.pacedRAuto
+    ),
+    new AnimMotionTestcase(
+      { path: "M100 200 L120 220 L130 210", rotate: "auto" },
+      _reusedCTMLists.pacedRAuto
+    ),
+    new AnimMotionTestcase(
+      { mpath: "M100 200 L120 220 L130 210", rotate: "auto" },
+      _reusedCTMLists.pacedRAuto
+    ),
+
+    // ..and now with rotate=auto-reverse
+    new AnimMotionTestcase(
+      { values: "100,200; 120,220; 130, 210", rotate: "auto-reverse" },
+      _reusedCTMLists.pacedRAutoReverse
+    ),
+    new AnimMotionTestcase(
+      { path: "M100 200 L120 220 L130 210", rotate: "auto-reverse" },
+      _reusedCTMLists.pacedRAutoReverse
+    ),
+    new AnimMotionTestcase(
+      { mpath: "M100 200 L120 220 L130 210", rotate: "auto-reverse" },
+      _reusedCTMLists.pacedRAutoReverse
+    ),
+  ]),
+
+  // Bundle to test calcMode='discrete'
+  new TestcaseBundle(gMotionAttr, [
+    new AnimMotionTestcase(
+      { values: "100, 200; 120, 220; 130, 210", calcMode: "discrete" },
+      _reusedCTMLists.discreteBasic
+    ),
+    new AnimMotionTestcase(
+      { path: "M100 200 L120 220 L130 210", calcMode: "discrete" },
+      _reusedCTMLists.discreteBasic
+    ),
+    new AnimMotionTestcase(
+      { mpath: "M100 200 L120 220 L130 210", calcMode: "discrete" },
+      _reusedCTMLists.discreteBasic
+    ),
+    // ..and now with rotate=auto
+    new AnimMotionTestcase(
+      {
+        values: "100, 200; 120, 220; 130, 210",
+        calcMode: "discrete",
+        rotate: "auto",
+      },
+      _reusedCTMLists.discreteRAuto
+    ),
+    new AnimMotionTestcase(
+      {
+        path: "M100 200 L120 220 L130 210",
+        calcMode: "discrete",
+        rotate: "auto",
+      },
+      _reusedCTMLists.discreteRAuto
+    ),
+    new AnimMotionTestcase(
+      {
+        mpath: "M100 200 L120 220 L130 210",
+        calcMode: "discrete",
+        rotate: "auto",
+      },
+      _reusedCTMLists.discreteRAuto
+    ),
+  ]),
+
+  // Bundle to test relative units ('em')
+  new TestcaseBundle(gMotionAttr, [
+    // First with unitless values from->by...
+    new AnimMotionTestcase(
+      { from: "10, 10", by: "30, 60" },
+      {
+        ctm0: [10, 10, 0],
+        ctm1_6: [15, 20, 0],
+        ctm1_3: [20, 30, 0],
+        ctm2_3: [30, 50, 0],
+        ctm1: [40, 70, 0],
+      }
+    ),
+    // ... then add 'em' units (with 1em=10px) on half the values
+    new AnimMotionTestcase(
+      { from: "1em, 10", by: "30, 6em" },
+      {
+        ctm0: [10, 10, 0],
+        ctm1_6: [15, 20, 0],
+        ctm1_3: [20, 30, 0],
+        ctm2_3: [30, 50, 0],
+        ctm1: [40, 70, 0],
+      }
+    ),
+  ]),
+
+  // Bundle to test a path with just a "move" command and nothing else
+  new TestcaseBundle(gMotionAttr, [
+    new AnimMotionTestcase({ values: "40, 80" }, _reusedCTMLists.justMoveBasic),
+    new AnimMotionTestcase({ path: "M40 80" }, _reusedCTMLists.justMoveBasic),
+    new AnimMotionTestcase({ mpath: "m40 80" }, _reusedCTMLists.justMoveBasic),
+  ]),
+  // ... and now with a fixed rotate-angle
+  new TestcaseBundle(gMotionAttr, [
+    new AnimMotionTestcase(
+      { values: "40, 80", rotate: "60" },
+      _reusedCTMLists.justMoveR60
+    ),
+    new AnimMotionTestcase(
+      { path: "M40 80", rotate: "60" },
+      _reusedCTMLists.justMoveR60
+    ),
+    new AnimMotionTestcase(
+      { mpath: "m40 80", rotate: "60" },
+      _reusedCTMLists.justMoveR60
+    ),
+  ]),
+  // ... and now with 'auto' (should use the move itself as
+  // our tangent angle, I think)
+  new TestcaseBundle(gMotionAttr, [
+    new AnimMotionTestcase(
+      { values: "40, 80", rotate: "auto" },
+      _reusedCTMLists.justMoveRAuto
+    ),
+    new AnimMotionTestcase(
+      { path: "M40 80", rotate: "auto" },
+      _reusedCTMLists.justMoveRAuto
+    ),
+    new AnimMotionTestcase(
+      { mpath: "m40 80", rotate: "auto" },
+      _reusedCTMLists.justMoveRAuto
+    ),
+  ]),
+  // ... and now with 'auto-reverse'
+  new TestcaseBundle(gMotionAttr, [
+    new AnimMotionTestcase(
+      { values: "40, 80", rotate: "auto-reverse" },
+      _reusedCTMLists.justMoveRAutoReverse
+    ),
+    new AnimMotionTestcase(
+      { path: "M40 80", rotate: "auto-reverse" },
+      _reusedCTMLists.justMoveRAutoReverse
+    ),
+    new AnimMotionTestcase(
+      { mpath: "m40 80", rotate: "auto-reverse" },
+      _reusedCTMLists.justMoveRAutoReverse
+    ),
+  ]),
+  // ... and now with a null move to make sure 'auto'/'auto-reverse' don't
+  // blow up
+  new TestcaseBundle(gMotionAttr, [
+    new AnimMotionTestcase(
+      { values: "0, 0", rotate: "auto" },
+      _reusedCTMLists.nullMoveBasic
+    ),
+  ]),
+  new TestcaseBundle(gMotionAttr, [
+    new AnimMotionTestcase(
+      { values: "0, 0", rotate: "auto-reverse" },
+      _reusedCTMLists.nullMoveRAutoReverse
+    ),
+  ]),
+];
+
+// XXXdholbert Add more tests:
+//  - keyPoints/keyTimes
+//  - paths with curves
+//  - Control path with from/by/to
diff --git a/dom/smil/test/db_smilCSSFromBy.js b/dom/smil/test/db_smilCSSFromBy.js
new file mode 100644
index 0000000000..737037271d
--- /dev/null
+++ b/dom/smil/test/db_smilCSSFromBy.js
@@ -0,0 +1,207 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 sw=2 sts=2 et: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* testcase data for simple "from-by" animations of CSS properties */
+
+// NOTE: This js file requires db_smilCSSPropertyList.js
+
+// Lists of testcases for re-use across multiple properties of the same type
+var _fromByTestLists = {
+  color: [
+    new AnimTestcaseFromBy("rgb(10, 20, 30)", "currentColor", {
+      midComp: "rgb(35, 45, 55)",
+      toComp: "rgb(60, 70, 80)",
+    }),
+    new AnimTestcaseFromBy("currentColor", "rgb(30, 20, 10)", {
+      fromComp: "rgb(50, 50, 50)",
+      midComp: "rgb(65, 60, 55)",
+      toComp: "rgb(80, 70, 60)",
+    }),
+    new AnimTestcaseFromBy(
+      "rgba(10, 20, 30, 0.2)",
+      "rgba(50, 50, 50, 1)",
+      // (rgb(10, 20, 30) * 0.2 * 0.5 + rgb(52, 54, 56) * 1.0 * 0.5) * (1 / 0.6)
+      {
+        midComp: "rgba(45, 48, 52, 0.6)",
+        // (rgb(10, 20, 30) * 0.2 + rgb(50, 50, 50) * 1) / 1.0
+        toComp: "rgb(52, 54, 56)",
+      }
+    ),
+
+    // The "from" and "by" values in the test case below overflow the maxium
+    // color-channel values when added together.
+    // (e.g. for red [ignoring alpha for now], 100 + 240 = 340 which is > 255)
+    //
+    // The SVG Animation spec says we should clamp color values "as late as
+    // possible" i.e. allow the channel overflow and clamp at paint-time.
+    //
+    // That gives us:
+    //
+    //   to-value = (rgb(100, 100, 100) * 0.6 + rgb(240, 240, 240) * 1.0)) * 1
+    //            = rgb(300, 300, 300)
+    //   midComp  = (rgb(100, 100, 100) * 0.6 * 0.5 + rgb(300, 300, 300) * 1.0 * 0.5) * (1 / 0.8)
+    //            = rgb(225, 225, 225)
+    //
+    //
+    new AnimTestcaseFromBy(
+      "rgba(100, 100, 100, 0.6)",
+      "rgba(240, 240, 240, 1)",
+      { midComp: "rgba(225, 225, 225, 0.8)", toComp: "rgb(255, 255, 255)" }
+    ),
+  ],
+  lengthNoUnits: [
+    new AnimTestcaseFromBy("0", "50", {
+      fromComp: "0px", // 0 acts like 0px
+      midComp: "25px",
+      toComp: "50px",
+    }),
+    new AnimTestcaseFromBy("30", "10", {
+      fromComp: "30px",
+      midComp: "35px",
+      toComp: "40px",
+    }),
+  ],
+  lengthPx: [
+    new AnimTestcaseFromBy("0px", "8px", {
+      fromComp: "0px",
+      midComp: "4px",
+      toComp: "8px",
+    }),
+    new AnimTestcaseFromBy("1px", "10px", {
+      fromComp: "1px",
+      midComp: "6px",
+      toComp: "11px",
+    }),
+  ],
+  opacity: [
+    new AnimTestcaseFromBy("1", "-1", { midComp: "0.5", toComp: "0" }),
+    new AnimTestcaseFromBy("0.4", "-0.6", { midComp: "0.1", toComp: "0" }),
+    new AnimTestcaseFromBy(
+      "0.8",
+      "-1.4",
+      { midComp: "0.1", toComp: "0" },
+      "opacities with abs val >1 get clamped too early"
+    ),
+    new AnimTestcaseFromBy(
+      "1.2",
+      "-0.6",
+      { midComp: "0.9", toComp: "0.6" },
+      "opacities with abs val >1 get clamped too early"
+    ),
+  ],
+  paint: [
+    // The "none" keyword & URI values aren't addiditve, so the animations in
+    // these testcases are expected to have no effect.
+    new AnimTestcaseFromBy("none", "none", { noEffect: 1 }),
+    new AnimTestcaseFromBy("url(#gradA)", "url(#gradB)", { noEffect: 1 }),
+    new AnimTestcaseFromBy("url(#gradA)", "url(#gradB) red", { noEffect: 1 }),
+    new AnimTestcaseFromBy("url(#gradA)", "none", { noEffect: 1 }),
+    new AnimTestcaseFromBy("red", "url(#gradA)", { noEffect: 1 }),
+  ],
+  URIsAndNone: [
+    // No need to specify { noEffect: 1 }, since plain URI-valued properties
+    // aren't additive
+    new AnimTestcaseFromBy("url(#idA)", "url(#idB)"),
+    new AnimTestcaseFromBy("none", "url(#idB)"),
+    new AnimTestcaseFromBy("url(#idB)", "inherit"),
+  ],
+};
+
+// List of attribute/testcase-list bundles to be tested
+var gFromByBundles = [
+  new TestcaseBundle(gPropList.clip, [
+    new AnimTestcaseFromBy(
+      "rect(1px, 2px, 3px, 4px)",
+      "rect(10px, 20px, 30px, 40px)",
+      {
+        midComp: "rect(6px, 12px, 18px, 24px)",
+        toComp: "rect(11px, 22px, 33px, 44px)",
+      }
+    ),
+    // Adding "auto" (either as a standalone value or a subcomponent value)
+    // should cause animation to fail.
+    new AnimTestcaseFromBy("auto", "auto", { noEffect: 1 }),
+    new AnimTestcaseFromBy("auto", "rect(auto, auto, auto, auto)", {
+      noEffect: 1,
+    }),
+    new AnimTestcaseFromBy(
+      "rect(auto, auto, auto, auto)",
+      "rect(auto, auto, auto, auto)",
+      { noEffect: 1 }
+    ),
+    new AnimTestcaseFromBy("rect(1px, 2px, 3px, 4px)", "auto", { noEffect: 1 }),
+    new AnimTestcaseFromBy("auto", "rect(1px, 2px, 3px, 4px)", { noEffect: 1 }),
+    new AnimTestcaseFromBy(
+      "rect(1px, 2px, 3px, auto)",
+      "rect(10px, 20px, 30px, 40px)",
+      { noEffect: 1 }
+    ),
+    new AnimTestcaseFromBy(
+      "rect(1px, auto, 3px, 4px)",
+      "rect(10px, auto, 30px, 40px)",
+      { noEffect: 1 }
+    ),
+    new AnimTestcaseFromBy(
+      "rect(1px, 2px, 3px, 4px)",
+      "rect(10px, auto, 30px, 40px)",
+      { noEffect: 1 }
+    ),
+  ]),
+  // Check that 'by' animations for 'cursor' has no effect
+  new TestcaseBundle(gPropList.cursor, [
+    new AnimTestcaseFromBy("crosshair", "move"),
+  ]),
+  new TestcaseBundle(
+    gPropList.fill,
+    [].concat(_fromByTestLists.color, _fromByTestLists.paint)
+  ),
+  // Check that 'by' animations involving URIs have no effect
+  new TestcaseBundle(gPropList.filter, _fromByTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.font, [
+    new AnimTestcaseFromBy(
+      "10px serif",
+      "normal normal 400 100px / 10px monospace"
+    ),
+  ]),
+  new TestcaseBundle(
+    gPropList.font_size,
+    [].concat(_fromByTestLists.lengthNoUnits, _fromByTestLists.lengthPx)
+  ),
+  new TestcaseBundle(gPropList.font_size_adjust, [
+    // These testcases implicitly have no effect, because font-size-adjust is
+    // non-additive (and is declared as such in db_smilCSSPropertyList.js)
+    new AnimTestcaseFromBy("0.5", "0.1"),
+    new AnimTestcaseFromBy("none", "0.1"),
+    new AnimTestcaseFromBy("0.1", "none"),
+  ]),
+  // Bug 1457353: Change from nsColor to StyleComplexColor causes addition
+  // with currentcolor to break. Bug 1465307 for work to re-enable.
+  new TestcaseBundle(gPropList.lighting_color, _fromByTestLists.color),
+  new TestcaseBundle(gPropList.marker, _fromByTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.marker_end, _fromByTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.marker_mid, _fromByTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.marker_start, _fromByTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.overflow, [
+    new AnimTestcaseFromBy("inherit", "auto"),
+    new AnimTestcaseFromBy("scroll", "hidden"),
+  ]),
+  new TestcaseBundle(gPropList.opacity, _fromByTestLists.opacity),
+  new TestcaseBundle(gPropList.stroke_miterlimit, [
+    new AnimTestcaseFromBy("1", "1", { midComp: "1.5", toComp: "2" }),
+    new AnimTestcaseFromBy("20.1", "-10", { midComp: "15.1", toComp: "10.1" }),
+  ]),
+  new TestcaseBundle(gPropList.stroke_dasharray, [
+    // These testcases implicitly have no effect, because stroke-dasharray is
+    // non-additive (and is declared as such in db_smilCSSPropertyList.js)
+    new AnimTestcaseFromBy("none", "5"),
+    new AnimTestcaseFromBy("10", "5"),
+    new AnimTestcaseFromBy("1", "2, 3"),
+  ]),
+  new TestcaseBundle(
+    gPropList.stroke_width,
+    [].concat(_fromByTestLists.lengthNoUnits, _fromByTestLists.lengthPx)
+  ),
+];
diff --git a/dom/smil/test/db_smilCSSFromTo.js b/dom/smil/test/db_smilCSSFromTo.js
new file mode 100644
index 0000000000..a644c96962
--- /dev/null
+++ b/dom/smil/test/db_smilCSSFromTo.js
@@ -0,0 +1,625 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 sw=2 sts=2 et: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* testcase data for simple "from-to" animations of CSS properties */
+
+// NOTE: This js file requires db_smilCSSPropertyList.js
+
+// NOTE: I'm Including 'inherit' and 'currentColor' as interpolatable values.
+// According to SVG Mobile 1.2 section 16.2.9, "keywords such as inherit which
+// yield a numeric computed value may be included in the values list for an
+// interpolated animation".
+
+// Path of test URL (stripping off final slash + filename), for use in
+// generating computed value of 'cursor' property
+var _testPath = document.URL.substring(0, document.URL.lastIndexOf("/"));
+
+// Lists of testcases for re-use across multiple properties of the same type
+var _fromToTestLists = {
+  color: [
+    new AnimTestcaseFromTo("rgb(100, 100, 100)", "rgb(200, 200, 200)", {
+      midComp: "rgb(150, 150, 150)",
+    }),
+    new AnimTestcaseFromTo("#F02000", "#0080A0", {
+      fromComp: "rgb(240, 32, 0)",
+      midComp: "rgb(120, 80, 80)",
+      toComp: "rgb(0, 128, 160)",
+    }),
+    new AnimTestcaseFromTo("crimson", "lawngreen", {
+      fromComp: "rgb(220, 20, 60)",
+      midComp: "rgb(172, 136, 30)",
+      toComp: "rgb(124, 252, 0)",
+    }),
+    new AnimTestcaseFromTo("currentColor", "rgb(100, 100, 100)", {
+      fromComp: "rgb(50, 50, 50)",
+      midComp: "rgb(75, 75, 75)",
+    }),
+    new AnimTestcaseFromTo(
+      "rgba(10, 20, 30, 0.2)",
+      "rgba(50, 50, 50, 1)",
+      // (rgb(10, 20, 30) * 0.2 * 0.5 + rgb(50, 50, 50) * 1.0 * 0.5) * (1 / 0.6)
+      { midComp: "rgba(43, 45, 47, 0.6)", toComp: "rgb(50, 50, 50)" }
+    ),
+  ],
+  colorFromInheritBlack: [
+    new AnimTestcaseFromTo("inherit", "rgb(200, 200, 200)", {
+      fromComp: "rgb(0, 0, 0)",
+      midComp: "rgb(100, 100, 100)",
+    }),
+  ],
+  colorFromInheritWhite: [
+    new AnimTestcaseFromTo("inherit", "rgb(205, 205, 205)", {
+      fromComp: "rgb(255, 255, 255)",
+      midComp: "rgb(230, 230, 230)",
+    }),
+  ],
+  paintServer: [
+    new AnimTestcaseFromTo("none", "none"),
+    new AnimTestcaseFromTo("none", "blue", { toComp: "rgb(0, 0, 255)" }),
+    new AnimTestcaseFromTo("rgb(50, 50, 50)", "none"),
+    new AnimTestcaseFromTo(
+      "url(#gradA)",
+      "url(#gradB) currentColor",
+      {
+        fromComp: 'url("' + document.URL + '#gradA") rgb(0, 0, 0)',
+        toComp: 'url("' + document.URL + '#gradB") rgb(50, 50, 50)',
+      },
+      "need support for URI-based paints"
+    ),
+    new AnimTestcaseFromTo(
+      "url(#gradA) orange",
+      "url(#gradB)",
+      {
+        fromComp: 'url("' + document.URL + '#gradA") rgb(255, 165, 0)',
+        toComp: 'url("' + document.URL + '#gradB") rgb(0, 0, 0)',
+      },
+      "need support for URI-based paints"
+    ),
+    new AnimTestcaseFromTo(
+      "url(#no_grad)",
+      "url(#gradB)",
+      {
+        fromComp: 'url("' + document.URL + '#no_grad") ' + "rgb(0, 0, 0)",
+        toComp: 'url("' + document.URL + '#gradB") rgb(0, 0, 0)',
+      },
+      "need support for URI-based paints"
+    ),
+    new AnimTestcaseFromTo(
+      "url(#no_grad) rgb(1,2,3)",
+      "url(#gradB) blue",
+      {
+        fromComp: 'url("' + document.URL + '#no_grad") ' + "rgb(1, 2, 3)",
+        toComp: 'url("' + document.URL + '#gradB") rgb(0, 0, 255)',
+      },
+      "need support for URI-based paints"
+    ),
+  ],
+  lengthNoUnits: [
+    new AnimTestcaseFromTo("0", "20", {
+      fromComp: "0px",
+      midComp: "10px",
+      toComp: "20px",
+    }),
+    new AnimTestcaseFromTo("50", "0", {
+      fromComp: "50px",
+      midComp: "25px",
+      toComp: "0px",
+    }),
+    new AnimTestcaseFromTo("30", "80", {
+      fromComp: "30px",
+      midComp: "55px",
+      toComp: "80px",
+    }),
+  ],
+  lengthPx: [
+    new AnimTestcaseFromTo("0px", "12px", {
+      fromComp: "0px",
+      midComp: "6px",
+      toComp: "12px",
+    }),
+    new AnimTestcaseFromTo("16px", "0px", {
+      fromComp: "16px",
+      midComp: "8px",
+      toComp: "0px",
+    }),
+    new AnimTestcaseFromTo("10px", "20px", {
+      fromComp: "10px",
+      midComp: "15px",
+      toComp: "20px",
+    }),
+    new AnimTestcaseFromTo("41px", "1px", {
+      fromComp: "41px",
+      midComp: "21px",
+      toComp: "1px",
+    }),
+  ],
+  lengthPctSVG: [new AnimTestcaseFromTo("20.5%", "0.5%", { midComp: "10.5%" })],
+  lengthPxPctSVG: [
+    new AnimTestcaseFromTo(
+      "10px",
+      "10%",
+      { midComp: "15px" },
+      "need support for interpolating between " + "px and percent values"
+    ),
+  ],
+  lengthPxNoUnitsSVG: [
+    new AnimTestcaseFromTo("10", "20px", {
+      fromComp: "10px",
+      midComp: "15px",
+      toComp: "20px",
+    }),
+    new AnimTestcaseFromTo("10px", "20", {
+      fromComp: "10px",
+      midComp: "15px",
+      toComp: "20px",
+    }),
+  ],
+  opacity: [
+    new AnimTestcaseFromTo("1", "0", { midComp: "0.5" }),
+    new AnimTestcaseFromTo("0.2", "0.12", { midComp: "0.16" }),
+    new AnimTestcaseFromTo("0.5", "0.7", { midComp: "0.6" }),
+    new AnimTestcaseFromTo("0.5", "inherit", { midComp: "0.75", toComp: "1" }),
+    // Make sure we don't clamp out-of-range values before interpolation
+    new AnimTestcaseFromTo(
+      "0.2",
+      "1.2",
+      { midComp: "0.7", toComp: "1" },
+      "opacities with abs val >1 get clamped too early"
+    ),
+    new AnimTestcaseFromTo("-0.2", "0.6", { fromComp: "0", midComp: "0.2" }),
+    new AnimTestcaseFromTo(
+      "-1.2",
+      "1.6",
+      { fromComp: "0", midComp: "0.2", toComp: "1" },
+      "opacities with abs val >1 get clamped too early"
+    ),
+    new AnimTestcaseFromTo(
+      "-0.6",
+      "1.4",
+      { fromComp: "0", midComp: "0.4", toComp: "1" },
+      "opacities with abs val >1 get clamped too early"
+    ),
+  ],
+  URIsAndNone: [
+    new AnimTestcaseFromTo("url(#idA)", "url(#idB)", {
+      fromComp: 'url("#idA")',
+      toComp: 'url("#idB")',
+    }),
+    new AnimTestcaseFromTo("none", "url(#idB)", { toComp: 'url("#idB")' }),
+    new AnimTestcaseFromTo("url(#idB)", "inherit", {
+      fromComp: 'url("#idB")',
+      toComp: "none",
+    }),
+  ],
+};
+
+function _tweakForLetterSpacing(testcases) {
+  return testcases.map(function (t) {
+    let valMap = Object.assign({}, t.computedValMap);
+    for (let prop of Object.keys(valMap)) {
+      if (valMap[prop] == "0px") {
+        valMap[prop] = "normal";
+      }
+    }
+    return new AnimTestcaseFromTo(t.from, t.to, valMap);
+  });
+}
+
+// List of attribute/testcase-list bundles to be tested
+var gFromToBundles = [
+  new TestcaseBundle(gPropList.clip, [
+    new AnimTestcaseFromTo(
+      "rect(1px, 2px, 3px, 4px)",
+      "rect(11px, 22px, 33px, 44px)",
+      { midComp: "rect(6px, 12px, 18px, 24px)" }
+    ),
+    new AnimTestcaseFromTo(
+      "rect(1px, auto, 3px, 4px)",
+      "rect(11px, auto, 33px, 44px)",
+      { midComp: "rect(6px, auto, 18px, 24px)" }
+    ),
+    new AnimTestcaseFromTo("auto", "auto"),
+    new AnimTestcaseFromTo(
+      "rect(auto, auto, auto, auto)",
+      "rect(auto, auto, auto, auto)"
+    ),
+    // Interpolation not supported in these next cases (with auto --> px-value)
+    new AnimTestcaseFromTo(
+      "rect(1px, auto, 3px, auto)",
+      "rect(11px, auto, 33px, 44px)"
+    ),
+    new AnimTestcaseFromTo(
+      "rect(1px, 2px, 3px, 4px)",
+      "rect(11px, auto, 33px, 44px)"
+    ),
+    new AnimTestcaseFromTo("rect(1px, 2px, 3px, 4px)", "auto"),
+    new AnimTestcaseFromTo("auto", "rect(1px, 2px, 3px, 4px)"),
+  ]),
+  new TestcaseBundle(gPropList.clip_path, _fromToTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.clip_rule, [
+    new AnimTestcaseFromTo("nonzero", "evenodd"),
+    new AnimTestcaseFromTo("evenodd", "inherit", { toComp: "nonzero" }),
+  ]),
+  new TestcaseBundle(
+    gPropList.color,
+    [].concat(_fromToTestLists.color, [
+      // Note: inherited value is rgb(50, 50, 50) (set on <svg>)
+      new AnimTestcaseFromTo("inherit", "rgb(200, 200, 200)", {
+        fromComp: "rgb(50, 50, 50)",
+        midComp: "rgb(125, 125, 125)",
+      }),
+    ])
+  ),
+  new TestcaseBundle(gPropList.color_interpolation, [
+    new AnimTestcaseFromTo("sRGB", "auto", { fromComp: "srgb" }),
+    new AnimTestcaseFromTo("inherit", "linearRGB", {
+      fromComp: "srgb",
+      toComp: "linearrgb",
+    }),
+  ]),
+  new TestcaseBundle(gPropList.color_interpolation_filters, [
+    new AnimTestcaseFromTo("sRGB", "auto", { fromComp: "srgb" }),
+    new AnimTestcaseFromTo("auto", "inherit", { toComp: "linearrgb" }),
+  ]),
+  new TestcaseBundle(gPropList.cursor, [
+    new AnimTestcaseFromTo("crosshair", "move"),
+    new AnimTestcaseFromTo(
+      "url('a.cur'), url('b.cur'), nw-resize",
+      "sw-resize",
+      {
+        fromComp:
+          'url("' +
+          _testPath +
+          '/a.cur"), ' +
+          'url("' +
+          _testPath +
+          '/b.cur"), ' +
+          "nw-resize",
+      }
+    ),
+  ]),
+  new TestcaseBundle(gPropList.direction, [
+    new AnimTestcaseFromTo("ltr", "rtl"),
+    new AnimTestcaseFromTo("rtl", "inherit"),
+  ]),
+  new TestcaseBundle(gPropList.display, [
+    // I'm not testing the "inherit" value for "display", because part of
+    // my test runs with "display: none" on everything, and so the
+    // inherited value isn't always the same.  (i.e. the computed value
+    // of 'inherit' will be different in different tests)
+    new AnimTestcaseFromTo("block", "table-cell"),
+    new AnimTestcaseFromTo("inline", "inline-table"),
+    new AnimTestcaseFromTo("table-row", "none"),
+  ]),
+  new TestcaseBundle(gPropList.dominant_baseline, [
+    new AnimTestcaseFromTo("alphabetic", "hanging"),
+    new AnimTestcaseFromTo("mathematical", "central"),
+    new AnimTestcaseFromTo("middle", "text-after-edge"),
+    new AnimTestcaseFromTo("text-before-edge", "auto"),
+    new AnimTestcaseFromTo("alphabetic", "inherit", { toComp: "auto" }),
+  ]),
+  // NOTE: Mozilla doesn't currently support "enable-background", but I'm
+  // testing it here in case we ever add support for it, because it's
+  // explicitly not animatable in the SVG spec.
+  new TestcaseBundle(gPropList.enable_background, [
+    new AnimTestcaseFromTo("new", "accumulate"),
+  ]),
+  new TestcaseBundle(
+    gPropList.fill,
+    [].concat(
+      _fromToTestLists.color,
+      _fromToTestLists.paintServer,
+      _fromToTestLists.colorFromInheritBlack
+    )
+  ),
+  new TestcaseBundle(gPropList.fill_opacity, _fromToTestLists.opacity),
+  new TestcaseBundle(gPropList.fill_rule, [
+    new AnimTestcaseFromTo("nonzero", "evenodd"),
+    new AnimTestcaseFromTo("evenodd", "inherit", { toComp: "nonzero" }),
+  ]),
+  new TestcaseBundle(gPropList.filter, _fromToTestLists.URIsAndNone),
+  new TestcaseBundle(
+    gPropList.flood_color,
+    [].concat(_fromToTestLists.color, _fromToTestLists.colorFromInheritBlack)
+  ),
+  new TestcaseBundle(gPropList.flood_opacity, _fromToTestLists.opacity),
+  new TestcaseBundle(gPropList.font, [
+    // NOTE: 'line-height' is hard-wired at 10px in test_smilCSSFromTo.xhtml
+    // because if it's not explicitly set, its value varies across platforms.
+    // NOTE: System font values can't be tested here, because their computed
+    // values vary from platform to platform.  However, they are tested
+    // visually, in the reftest "anim-css-font-1.svg"
+    new AnimTestcaseFromTo("10px serif", "30px serif", {
+      fromComp: "normal normal 400 10px / 10px serif",
+      toComp: "normal normal 400 30px / 10px serif",
+    }),
+    new AnimTestcaseFromTo("10px serif", "30px sans-serif", {
+      fromComp: "normal normal 400 10px / 10px serif",
+      toComp: "normal normal 400 30px / 10px sans-serif",
+    }),
+    new AnimTestcaseFromTo("1px / 90px cursive", "100px monospace", {
+      fromComp: "normal normal 400 1px / 10px cursive",
+      toComp: "normal normal 400 100px / 10px monospace",
+    }),
+    new AnimTestcaseFromTo(
+      "italic small-caps 200 1px cursive",
+      "100px monospace",
+      {
+        fromComp: "italic small-caps 200 1px / 10px cursive",
+        toComp: "normal normal 400 100px / 10px monospace",
+      }
+    ),
+    new AnimTestcaseFromTo(
+      "oblique normal 200 30px / 10px cursive",
+      "normal small-caps 800 40px / 10px serif"
+    ),
+  ]),
+  new TestcaseBundle(gPropList.font_family, [
+    new AnimTestcaseFromTo("serif", "sans-serif"),
+    new AnimTestcaseFromTo("cursive", "monospace"),
+  ]),
+  new TestcaseBundle(
+    gPropList.font_size,
+    [].concat(_fromToTestLists.lengthNoUnits, _fromToTestLists.lengthPx, [
+      new AnimTestcaseFromTo("10px", "40%", {
+        midComp: "15px",
+        toComp: "20px",
+      }),
+      new AnimTestcaseFromTo("160%", "80%", {
+        fromComp: "80px",
+        midComp: "60px",
+        toComp: "40px",
+      }),
+    ])
+  ),
+  new TestcaseBundle(gPropList.font_size_adjust, [
+    new AnimTestcaseFromTo("0.9", "0.1", { midComp: "0.5" }),
+    new AnimTestcaseFromTo("0.5", "0.6", { midComp: "0.55" }),
+    new AnimTestcaseFromTo("none", "0.4"),
+  ]),
+  new TestcaseBundle(gPropList.font_stretch, [
+    new AnimTestcaseFromTo(
+      "normal",
+      "wider",
+      {},
+      "need support for animating between " + "relative 'font-stretch' values"
+    ),
+    new AnimTestcaseFromTo(
+      "narrower",
+      "ultra-condensed",
+      {},
+      "need support for animating between " + "relative 'font-stretch' values"
+    ),
+    new AnimTestcaseFromTo("ultra-condensed", "condensed", {
+      fromComp: "50%",
+      midComp: "62.5%",
+      toComp: "75%",
+    }),
+    new AnimTestcaseFromTo("semi-condensed", "semi-expanded", {
+      fromComp: "87.5%",
+      midComp: "100%",
+      toComp: "112.5%",
+    }),
+    new AnimTestcaseFromTo("expanded", "ultra-expanded", {
+      fromComp: "125%",
+      midComp: "162.5%",
+      toComp: "200%",
+    }),
+    new AnimTestcaseFromTo("ultra-expanded", "inherit", {
+      fromComp: "200%",
+      midComp: "150%",
+      toComp: "100%",
+    }),
+  ]),
+  new TestcaseBundle(gPropList.font_style, [
+    new AnimTestcaseFromTo("italic", "inherit", { toComp: "normal" }),
+    new AnimTestcaseFromTo("normal", "italic"),
+    new AnimTestcaseFromTo("italic", "oblique"),
+    new AnimTestcaseFromTo("oblique", "normal", { midComp: "oblique 7deg" }),
+  ]),
+  new TestcaseBundle(gPropList.font_variant, [
+    new AnimTestcaseFromTo("inherit", "small-caps", { fromComp: "normal" }),
+    new AnimTestcaseFromTo("small-caps", "normal"),
+  ]),
+  new TestcaseBundle(gPropList.font_weight, [
+    new AnimTestcaseFromTo("100", "900", { midComp: "500" }),
+    new AnimTestcaseFromTo("700", "100", { midComp: "400" }),
+    new AnimTestcaseFromTo("inherit", "200", {
+      fromComp: "400",
+      midComp: "300",
+    }),
+    new AnimTestcaseFromTo("normal", "bold", {
+      fromComp: "400",
+      midComp: "550",
+      toComp: "700",
+    }),
+    new AnimTestcaseFromTo(
+      "lighter",
+      "bolder",
+      {},
+      "need support for animating between " + "relative 'font-weight' values"
+    ),
+  ]),
+  // NOTE: Mozilla doesn't currently support "glyph-orientation-horizontal" or
+  // "glyph-orientation-vertical", but I'm testing them here in case we ever
+  // add support for them, because they're explicitly not animatable in the SVG
+  // spec.
+  new TestcaseBundle(gPropList.glyph_orientation_horizontal, [
+    new AnimTestcaseFromTo("45deg", "60deg"),
+  ]),
+  new TestcaseBundle(gPropList.glyph_orientation_vertical, [
+    new AnimTestcaseFromTo("45deg", "60deg"),
+  ]),
+  new TestcaseBundle(gPropList.image_rendering, [
+    new AnimTestcaseFromTo("auto", "optimizeQuality", {
+      toComp: "optimizequality",
+    }),
+    new AnimTestcaseFromTo("optimizeQuality", "optimizeSpeed", {
+      fromComp: "optimizequality",
+      toComp: "optimizespeed",
+    }),
+  ]),
+  new TestcaseBundle(
+    gPropList.letter_spacing,
+    _tweakForLetterSpacing(
+      [].concat(_fromToTestLists.lengthNoUnits, _fromToTestLists.lengthPx)
+    )
+  ),
+  new TestcaseBundle(
+    gPropList.lighting_color,
+    [].concat(_fromToTestLists.color, _fromToTestLists.colorFromInheritWhite)
+  ),
+  new TestcaseBundle(gPropList.marker, _fromToTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.marker_end, _fromToTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.marker_mid, _fromToTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.marker_start, _fromToTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.mask, _fromToTestLists.URIsAndNone),
+  new TestcaseBundle(gPropList.opacity, _fromToTestLists.opacity),
+  new TestcaseBundle(gPropList.overflow, [
+    new AnimTestcaseFromTo("auto", "visible"),
+    new AnimTestcaseFromTo("inherit", "visible", { fromComp: "hidden" }),
+    new AnimTestcaseFromTo("scroll", "auto"),
+  ]),
+  new TestcaseBundle(gPropList.pointer_events, [
+    new AnimTestcaseFromTo("visibleFill", "stroke", {
+      fromComp: "visiblefill",
+    }),
+    new AnimTestcaseFromTo("none", "visibleStroke", {
+      toComp: "visiblestroke",
+    }),
+  ]),
+  new TestcaseBundle(gPropList.shape_rendering, [
+    new AnimTestcaseFromTo("auto", "optimizeSpeed", {
+      toComp: "optimizespeed",
+    }),
+    new AnimTestcaseFromTo("crispEdges", "geometricPrecision", {
+      fromComp: "crispedges",
+      toComp: "geometricprecision",
+    }),
+  ]),
+  new TestcaseBundle(
+    gPropList.stop_color,
+    [].concat(_fromToTestLists.color, _fromToTestLists.colorFromInheritBlack)
+  ),
+  new TestcaseBundle(gPropList.stop_opacity, _fromToTestLists.opacity),
+  new TestcaseBundle(
+    gPropList.stroke,
+    [].concat(_fromToTestLists.color, _fromToTestLists.paintServer, [
+      // Note: inherited value is "none" (the default for "stroke" property)
+      new AnimTestcaseFromTo("inherit", "rgb(200, 200, 200)", {
+        fromComp: "none",
+      }),
+    ])
+  ),
+  new TestcaseBundle(
+    gPropList.stroke_dasharray,
+    [].concat(_fromToTestLists.lengthPctSVG, [
+      new AnimTestcaseFromTo("inherit", "20", { fromComp: "none" }),
+      new AnimTestcaseFromTo("1", "none"),
+      new AnimTestcaseFromTo("10", "20", { midComp: "15" }),
+      new AnimTestcaseFromTo("1", "2, 3", {
+        fromComp: "1, 1",
+        midComp: "1.5, 2",
+      }),
+      new AnimTestcaseFromTo("2, 8", "6", { midComp: "4, 7" }),
+      new AnimTestcaseFromTo("1, 3", "1, 3, 5, 7, 9", {
+        fromComp: "1, 3, 1, 3, 1, 3, 1, 3, 1, 3",
+        midComp: "1, 3, 3, 5, 5, 2, 2, 4, 4, 6",
+      }),
+    ])
+  ),
+  new TestcaseBundle(
+    gPropList.stroke_dashoffset,
+    [].concat(
+      _fromToTestLists.lengthNoUnits,
+      _fromToTestLists.lengthPx,
+      _fromToTestLists.lengthPxPctSVG,
+      _fromToTestLists.lengthPctSVG,
+      _fromToTestLists.lengthPxNoUnitsSVG
+    )
+  ),
+  new TestcaseBundle(gPropList.stroke_linecap, [
+    new AnimTestcaseFromTo("butt", "round"),
+    new AnimTestcaseFromTo("round", "square"),
+  ]),
+  new TestcaseBundle(gPropList.stroke_linejoin, [
+    new AnimTestcaseFromTo("miter", "round"),
+    new AnimTestcaseFromTo("round", "bevel"),
+  ]),
+  new TestcaseBundle(gPropList.stroke_miterlimit, [
+    new AnimTestcaseFromTo("1", "2", { midComp: "1.5" }),
+    new AnimTestcaseFromTo("20.1", "10.1", { midComp: "15.1" }),
+  ]),
+  new TestcaseBundle(gPropList.stroke_opacity, _fromToTestLists.opacity),
+  new TestcaseBundle(
+    gPropList.stroke_width,
+    [].concat(
+      _fromToTestLists.lengthNoUnits,
+      _fromToTestLists.lengthPx,
+      _fromToTestLists.lengthPxPctSVG,
+      _fromToTestLists.lengthPctSVG,
+      _fromToTestLists.lengthPxNoUnitsSVG,
+      [
+        new AnimTestcaseFromTo("inherit", "7px", {
+          fromComp: "1px",
+          midComp: "4px",
+          toComp: "7px",
+        }),
+      ]
+    )
+  ),
+  new TestcaseBundle(gPropList.text_anchor, [
+    new AnimTestcaseFromTo("start", "middle"),
+    new AnimTestcaseFromTo("middle", "end"),
+  ]),
+  new TestcaseBundle(gPropList.text_decoration_line, [
+    new AnimTestcaseFromTo("none", "underline"),
+    new AnimTestcaseFromTo("overline", "line-through"),
+    new AnimTestcaseFromTo("blink", "underline"),
+  ]),
+  new TestcaseBundle(gPropList.text_rendering, [
+    new AnimTestcaseFromTo("auto", "optimizeSpeed", {
+      toComp: "optimizespeed",
+    }),
+    new AnimTestcaseFromTo("optimizeSpeed", "geometricPrecision", {
+      fromComp: "optimizespeed",
+      toComp: "geometricprecision",
+    }),
+    new AnimTestcaseFromTo("geometricPrecision", "optimizeLegibility", {
+      fromComp: "geometricprecision",
+      toComp: "optimizelegibility",
+    }),
+  ]),
+  new TestcaseBundle(gPropList.unicode_bidi, [
+    new AnimTestcaseFromTo("embed", "bidi-override"),
+  ]),
+  new TestcaseBundle(gPropList.vector_effect, [
+    new AnimTestcaseFromTo("none", "non-scaling-stroke"),
+  ]),
+  new TestcaseBundle(gPropList.visibility, [
+    new AnimTestcaseFromTo("visible", "hidden"),
+    new AnimTestcaseFromTo("hidden", "collapse"),
+  ]),
+  new TestcaseBundle(
+    gPropList.word_spacing,
+    [].concat(
+      _fromToTestLists.lengthNoUnits,
+      _fromToTestLists.lengthPx,
+      _fromToTestLists.lengthPxPctSVG
+    )
+  ),
+  new TestcaseBundle(
+    gPropList.word_spacing,
+    _fromToTestLists.lengthPctSVG,
+    "pct->pct animations don't currently work for " + "*-spacing properties"
+  ),
+  // NOTE: Mozilla doesn't currently support "writing-mode", but I'm
+  // testing it here in case we ever add support for it, because it's
+  // explicitly not animatable in the SVG spec.
+  new TestcaseBundle(gPropList.writing_mode, [
+    new AnimTestcaseFromTo("lr", "rl"),
+  ]),
+];
diff --git a/dom/smil/test/db_smilCSSPaced.js b/dom/smil/test/db_smilCSSPaced.js
new file mode 100644
index 0000000000..de2896bd2b
--- /dev/null
+++ b/dom/smil/test/db_smilCSSPaced.js
@@ -0,0 +1,356 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+/* vim: set shiftwidth=4 tabstop=4 autoindent cindent noexpandtab: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* testcase data for paced-mode animations of CSS properties */
+
+// Lists of testcases for re-use across multiple properties of the same type
+var _pacedTestLists = {
+  color: [
+    new AnimTestcasePaced(
+      "rgb(2,  4,  6); " + "rgb(4,  8, 12); " + "rgb(8, 16, 24)",
+      {
+        comp0: "rgb(2, 4, 6)",
+        comp1_6: "rgb(3, 6, 9)",
+        comp1_3: "rgb(4, 8, 12)",
+        comp2_3: "rgb(6, 12, 18)",
+        comp1: "rgb(8, 16, 24)",
+      }
+    ),
+    new AnimTestcasePaced(
+      "rgb(10, 10, 10); " + "rgb(20, 10, 8); " + "rgb(20, 30, 4)",
+      {
+        comp0: "rgb(10, 10, 10)",
+        comp1_6: "rgb(15, 10, 9)",
+        comp1_3: "rgb(20, 10, 8)",
+        comp2_3: "rgb(20, 20, 6)",
+        comp1: "rgb(20, 30, 4)",
+      }
+    ),
+    // Use the same RGB component values to make
+    // premultication effect easier to compute.
+    new AnimTestcasePaced(
+      "rgba(20, 40, 60, 0.2); " +
+        "rgba(20, 40, 60, 0.4); " +
+        "rgba(20, 40, 60, 0.8)",
+      {
+        comp0: "rgba(20, 40, 60, 0.2)",
+        comp1_6: "rgba(20, 40, 60, 0.3)",
+        comp1_3: "rgba(20, 40, 60, 0.4)",
+        comp2_3: "rgba(20, 40, 60, 0.6)",
+        comp1: "rgba(20, 40, 60, 0.8)",
+      }
+    ),
+  ],
+  currentColor_color: [
+    new AnimTestcasePaced(
+      "olive; " + // rgb(128, 128, 0)
+        "currentColor; " + // rgb(50, 50, 50)
+        "rgb(206, 150, 206)",
+      {
+        comp0: "rgb(128, 128, 0)",
+        comp1_6: "rgb(89, 89, 25)",
+        comp1_3: "rgb(50, 50, 50)",
+        comp2_3: "rgb(128, 100, 128)",
+        comp1: "rgb(206, 150, 206)",
+      }
+    ),
+  ],
+  currentColor_fill: [
+    // Bug 1467622 changed the distance calculation
+    // involving currentColor, comp values below
+    // are no longer evenly spaced.
+    new AnimTestcasePaced(
+      "olive; " + // rgb(128, 128, 0)
+        "currentColor; " + // rgb(50, 50, 50)
+        "rgb(206, 150, 206)",
+      {
+        comp0: "rgb(128, 128, 0)",
+        comp1_6: "rgb(98, 98, 19)",
+        comp1_3: "rgb(67, 67, 39)",
+        comp2_3: "rgb(115, 92, 115)",
+        comp1: "rgb(206, 150, 206)",
+      }
+    ),
+  ],
+  paintServer: [
+    // Sanity check: These aren't interpolatable -- they should end up
+    // ignoring the calcMode="paced" and falling into discrete-mode.
+    new AnimTestcasePaced(
+      "url(#gradA); url(#gradB)",
+      {
+        comp0: 'url("' + document.URL + '#gradA") rgb(0, 0, 0)',
+        comp1_6: 'url("' + document.URL + '#gradA") rgb(0, 0, 0)',
+        comp1_3: 'url("' + document.URL + '#gradA") rgb(0, 0, 0)',
+        comp2_3: 'url("' + document.URL + '#gradB") rgb(0, 0, 0)',
+        comp1: 'url("' + document.URL + '#gradB") rgb(0, 0, 0)',
+      },
+      "need support for URI-based paints"
+    ),
+    new AnimTestcasePaced(
+      "url(#gradA); url(#gradB); url(#gradC)",
+      {
+        comp0: 'url("' + document.URL + '#gradA") rgb(0, 0, 0)',
+        comp1_6: 'url("' + document.URL + '#gradA") rgb(0, 0, 0)',
+        comp1_3: 'url("' + document.URL + '#gradB") rgb(0, 0, 0)',
+        comp2_3: 'url("' + document.URL + '#gradC") rgb(0, 0, 0)',
+        comp1: 'url("' + document.URL + '#gradC") rgb(0, 0, 0)',
+      },
+      "need support for URI-based paints"
+    ),
+  ],
+  lengthNoUnits: [
+    new AnimTestcasePaced("2; 0; 4", {
+      comp0: "2px",
+      comp1_6: "1px",
+      comp1_3: "0px",
+      comp2_3: "2px",
+      comp1: "4px",
+    }),
+    new AnimTestcasePaced("10; 12; 8", {
+      comp0: "10px",
+      comp1_6: "11px",
+      comp1_3: "12px",
+      comp2_3: "10px",
+      comp1: "8px",
+    }),
+  ],
+  lengthPx: [
+    new AnimTestcasePaced("0px; 2px; 6px", {
+      comp0: "0px",
+      comp1_6: "1px",
+      comp1_3: "2px",
+      comp2_3: "4px",
+      comp1: "6px",
+    }),
+    new AnimTestcasePaced("10px; 12px; 8px", {
+      comp0: "10px",
+      comp1_6: "11px",
+      comp1_3: "12px",
+      comp2_3: "10px",
+      comp1: "8px",
+    }),
+  ],
+  lengthPctSVG: [
+    new AnimTestcasePaced("5%; 6%; 4%", {
+      comp0: "5%",
+      comp1_6: "5.5%",
+      comp1_3: "6%",
+      comp2_3: "5%",
+      comp1: "4%",
+    }),
+  ],
+  lengthPxPctSVG: [
+    new AnimTestcasePaced(
+      "0px; 1%; 6px",
+      {
+        comp0: "0px",
+        comp1_6: "1px",
+        comp1_3: "1%",
+        comp2_3: "4px",
+        comp1: "6px",
+      },
+      "need support for interpolating between " + "px and percent values"
+    ),
+  ],
+  opacity: [
+    new AnimTestcasePaced("0; 0.2; 0.6", {
+      comp0: "0",
+      comp1_6: "0.1",
+      comp1_3: "0.2",
+      comp2_3: "0.4",
+      comp1: "0.6",
+    }),
+    new AnimTestcasePaced("0.7; 1.0; 0.4", {
+      comp0: "0.7",
+      comp1_6: "0.85",
+      comp1_3: "1",
+      comp2_3: "0.7",
+      comp1: "0.4",
+    }),
+  ],
+  rect: [
+    new AnimTestcasePaced(
+      "rect(2px, 4px, 6px, 8px); " +
+        "rect(4px, 8px, 12px, 16px); " +
+        "rect(8px, 16px, 24px, 32px)",
+      {
+        comp0: "rect(2px, 4px, 6px, 8px)",
+        comp1_6: "rect(3px, 6px, 9px, 12px)",
+        comp1_3: "rect(4px, 8px, 12px, 16px)",
+        comp2_3: "rect(6px, 12px, 18px, 24px)",
+        comp1: "rect(8px, 16px, 24px, 32px)",
+      }
+    ),
+    new AnimTestcasePaced(
+      "rect(10px, 10px, 10px, 10px); " +
+        "rect(20px, 10px, 50px, 8px); " +
+        "rect(20px, 30px, 130px, 4px)",
+      {
+        comp0: "rect(10px, 10px, 10px, 10px)",
+        comp1_6: "rect(15px, 10px, 30px, 9px)",
+        comp1_3: "rect(20px, 10px, 50px, 8px)",
+        comp2_3: "rect(20px, 20px, 90px, 6px)",
+        comp1: "rect(20px, 30px, 130px, 4px)",
+      }
+    ),
+    new AnimTestcasePaced(
+      "rect(10px, auto, 10px, 10px); " +
+        "rect(20px, auto, 50px, 8px); " +
+        "rect(40px, auto, 130px, 4px)",
+      {
+        comp0: "rect(10px, auto, 10px, 10px)",
+        comp1_6: "rect(15px, auto, 30px, 9px)",
+        comp1_3: "rect(20px, auto, 50px, 8px)",
+        comp2_3: "rect(30px, auto, 90px, 6px)",
+        comp1: "rect(40px, auto, 130px, 4px)",
+      }
+    ),
+    // Paced-mode animation is not supported in these next few cases
+    // (Can't compute subcomponent distance between 'auto' & px-values)
+    new AnimTestcasePaced(
+      "rect(10px, 10px, 10px, auto); " +
+        "rect(20px, 10px, 50px, 8px); " +
+        "rect(20px, 30px, 130px, 4px)",
+      {
+        comp0: "rect(10px, 10px, 10px, auto)",
+        comp1_6: "rect(10px, 10px, 10px, auto)",
+        comp1_3: "rect(20px, 10px, 50px, 8px)",
+        comp2_3: "rect(20px, 30px, 130px, 4px)",
+        comp1: "rect(20px, 30px, 130px, 4px)",
+      }
+    ),
+    new AnimTestcasePaced(
+      "rect(10px, 10px, 10px, 10px); " +
+        "rect(20px, 10px, 50px, 8px); " +
+        "auto",
+      {
+        comp0: "rect(10px, 10px, 10px, 10px)",
+        comp1_6: "rect(10px, 10px, 10px, 10px)",
+        comp1_3: "rect(20px, 10px, 50px, 8px)",
+        comp2_3: "auto",
+        comp1: "auto",
+      }
+    ),
+    new AnimTestcasePaced(
+      "auto; " + "auto; " + "rect(20px, 30px, 130px, 4px)",
+      {
+        comp0: "auto",
+        comp1_6: "auto",
+        comp1_3: "auto",
+        comp2_3: "rect(20px, 30px, 130px, 4px)",
+        comp1: "rect(20px, 30px, 130px, 4px)",
+      }
+    ),
+    new AnimTestcasePaced("auto; auto; auto", {
+      comp0: "auto",
+      comp1_6: "auto",
+      comp1_3: "auto",
+      comp2_3: "auto",
+      comp1: "auto",
+    }),
+  ],
+};
+
+// TODO: test more properties here.
+var gPacedBundles = [
+  new TestcaseBundle(gPropList.clip, _pacedTestLists.rect),
+  new TestcaseBundle(
+    gPropList.color,
+    [].concat(_pacedTestLists.color, _pacedTestLists.currentColor_color)
+  ),
+  new TestcaseBundle(gPropList.direction, [
+    new AnimTestcasePaced("rtl; ltr; rtl"),
+  ]),
+  new TestcaseBundle(
+    gPropList.fill,
+    [].concat(
+      _pacedTestLists.color,
+      _pacedTestLists.currentColor_fill,
+      _pacedTestLists.paintServer
+    )
+  ),
+  new TestcaseBundle(
+    gPropList.font_size,
+    [].concat(_pacedTestLists.lengthNoUnits, _pacedTestLists.lengthPx, [
+      new AnimTestcasePaced("20%; 24%; 16%", {
+        comp0: "10px",
+        comp1_6: "11px",
+        comp1_3: "12px",
+        comp2_3: "10px",
+        comp1: "8px",
+      }),
+      new AnimTestcasePaced("0px; 4%; 6px", {
+        comp0: "0px",
+        comp1_6: "1px",
+        comp1_3: "2px",
+        comp2_3: "4px",
+        comp1: "6px",
+      }),
+    ])
+  ),
+  new TestcaseBundle(gPropList.font_size_adjust, [
+    new AnimTestcasePaced("0.2; 0.6; 0.8", {
+      comp0: "0.2",
+      comp1_6: "0.3",
+      comp1_3: "0.4",
+      comp2_3: "0.6",
+      comp1: "0.8",
+    }),
+    new AnimTestcasePaced("none; none; 0.5", {
+      comp0: "none",
+      comp1_6: "none",
+      comp1_3: "none",
+      comp2_3: "0.5",
+      comp1: "0.5",
+    }),
+  ]),
+  new TestcaseBundle(gPropList.font_family, [
+    // Sanity check: 'font-family' isn't interpolatable.  It should end up
+    // ignoring the calcMode="paced" and falling into discrete-mode.
+    new AnimTestcasePaced(
+      "serif; sans-serif; monospace",
+      {
+        comp0: "serif",
+        comp1_6: "serif",
+        comp1_3: "sans-serif",
+        comp2_3: "monospace",
+        comp1: "monospace",
+      },
+      "need support for more font properties"
+    ),
+  ]),
+  new TestcaseBundle(gPropList.opacity, _pacedTestLists.opacity),
+  new TestcaseBundle(
+    gPropList.stroke_dasharray,
+    [].concat(_pacedTestLists.lengthPctSVG, [
+      new AnimTestcasePaced("7, 7, 7; 7, 10, 3; 1, 2, 3", {
+        comp0: "7px, 7px, 7px",
+        comp1_6: "7px, 8.5px, 5px",
+        comp1_3: "7px, 10px, 3px",
+        comp2_3: "4px, 6px, 3px",
+        comp1: "1px, 2px, 3px",
+      }),
+    ])
+  ),
+  new TestcaseBundle(
+    gPropList.stroke_dashoffset,
+    [].concat(
+      _pacedTestLists.lengthNoUnits,
+      _pacedTestLists.lengthPx,
+      _pacedTestLists.lengthPctSVG,
+      _pacedTestLists.lengthPxPctSVG
+    )
+  ),
+  new TestcaseBundle(
+    gPropList.stroke_width,
+    [].concat(
+      _pacedTestLists.lengthNoUnits,
+      _pacedTestLists.lengthPx,
+      _pacedTestLists.lengthPctSVG,
+      _pacedTestLists.lengthPxPctSVG
+    )
+  ),
+];
diff --git a/dom/smil/test/db_smilCSSPropertyList.js b/dom/smil/test/db_smilCSSPropertyList.js
new file mode 100644
index 0000000000..237c9db585
--- /dev/null
+++ b/dom/smil/test/db_smilCSSPropertyList.js
@@ -0,0 +1,104 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 sw=2 sts=2 et: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* list of CSS properties recognized by SVG 1.1 spec, for use in mochitests */
+
+// List of CSS Properties from SVG 1.1 Specification, Appendix N
+var gPropList = {
+  // NOTE: AnimatedAttribute signature is:
+  //  (attrName, attrType, sampleTarget, isAnimatable, isAdditive)
+
+  // SKIP 'alignment-baseline' property: animatable but not supported by Mozilla
+  // SKIP 'baseline-shift' property: animatable but not supported by Mozilla
+  clip: new AdditiveAttribute("clip", "CSS", "marker"),
+  clip_path: new NonAdditiveAttribute("clip-path", "CSS", "rect"),
+  clip_rule: new NonAdditiveAttribute("clip-rule", "CSS", "circle"),
+  color: new AdditiveAttribute("color", "CSS", "rect"),
+  color_interpolation: new NonAdditiveAttribute(
+    "color-interpolation",
+    "CSS",
+    "rect"
+  ),
+  color_interpolation_filters: new NonAdditiveAttribute(
+    "color-interpolation-filters",
+    "CSS",
+    "feFlood"
+  ),
+  // SKIP 'color-profile' property: animatable but not supported by Mozilla
+  cursor: new NonAdditiveAttribute("cursor", "CSS", "rect"),
+  direction: new NonAnimatableAttribute("direction", "CSS", "text"),
+  display: new NonAdditiveAttribute("display", "CSS", "rect"),
+  dominant_baseline: new NonAdditiveAttribute(
+    "dominant-baseline",
+    "CSS",
+    "text"
+  ),
+  enable_background:
+    // NOTE: Not supported by Mozilla, but explicitly non-animatable
+    new NonAnimatableAttribute("enable-background", "CSS", "marker"),
+  fill: new AdditiveAttribute("fill", "CSS", "rect"),
+  fill_opacity: new AdditiveAttribute("fill-opacity", "CSS", "rect"),
+  fill_rule: new NonAdditiveAttribute("fill-rule", "CSS", "rect"),
+  filter: new NonAdditiveAttribute("filter", "CSS", "rect"),
+  flood_color: new AdditiveAttribute("flood-color", "CSS", "feFlood"),
+  flood_opacity: new AdditiveAttribute("flood-opacity", "CSS", "feFlood"),
+  font: new NonAdditiveAttribute("font", "CSS", "text"),
+  font_family: new NonAdditiveAttribute("font-family", "CSS", "text"),
+  font_size: new AdditiveAttribute("font-size", "CSS", "text"),
+  font_size_adjust: new NonAdditiveAttribute("font-size-adjust", "CSS", "text"),
+  font_stretch: new NonAdditiveAttribute("font-stretch", "CSS", "text"),
+  font_style: new NonAdditiveAttribute("font-style", "CSS", "text"),
+  font_variant: new NonAdditiveAttribute("font-variant", "CSS", "text"),
+  // XXXdholbert should 'font-weight' be additive?
+  font_weight: new NonAdditiveAttribute("font-weight", "CSS", "text"),
+  glyph_orientation_horizontal:
+    // NOTE: Not supported by Mozilla, but explicitly non-animatable
+    NonAnimatableAttribute("glyph-orientation-horizontal", "CSS", "text"),
+  glyph_orientation_vertical:
+    // NOTE: Not supported by Mozilla, but explicitly non-animatable
+    NonAnimatableAttribute("glyph-orientation-horizontal", "CSS", "text"),
+  image_rendering: NonAdditiveAttribute("image-rendering", "CSS", "image"),
+  // SKIP 'kerning' property: animatable but not supported by Mozilla
+  letter_spacing: new AdditiveAttribute("letter-spacing", "CSS", "text"),
+  lighting_color: new AdditiveAttribute(
+    "lighting-color",
+    "CSS",
+    "feDiffuseLighting"
+  ),
+  marker: new NonAdditiveAttribute("marker", "CSS", "line"),
+  marker_end: new NonAdditiveAttribute("marker-end", "CSS", "line"),
+  marker_mid: new NonAdditiveAttribute("marker-mid", "CSS", "line"),
+  marker_start: new NonAdditiveAttribute("marker-start", "CSS", "line"),
+  mask: new NonAdditiveAttribute("mask", "CSS", "line"),
+  opacity: new AdditiveAttribute("opacity", "CSS", "rect"),
+  overflow: new NonAdditiveAttribute("overflow", "CSS", "marker"),
+  pointer_events: new NonAdditiveAttribute("pointer-events", "CSS", "rect"),
+  shape_rendering: new NonAdditiveAttribute("shape-rendering", "CSS", "rect"),
+  stop_color: new AdditiveAttribute("stop-color", "CSS", "stop"),
+  stop_opacity: new AdditiveAttribute("stop-opacity", "CSS", "stop"),
+  stroke: new AdditiveAttribute("stroke", "CSS", "rect"),
+  stroke_dasharray: new NonAdditiveAttribute("stroke-dasharray", "CSS", "rect"),
+  stroke_dashoffset: new AdditiveAttribute("stroke-dashoffset", "CSS", "rect"),
+  stroke_linecap: new NonAdditiveAttribute("stroke-linecap", "CSS", "rect"),
+  stroke_linejoin: new NonAdditiveAttribute("stroke-linejoin", "CSS", "rect"),
+  stroke_miterlimit: new AdditiveAttribute("stroke-miterlimit", "CSS", "rect"),
+  stroke_opacity: new AdditiveAttribute("stroke-opacity", "CSS", "rect"),
+  stroke_width: new AdditiveAttribute("stroke-width", "CSS", "rect"),
+  text_anchor: new NonAdditiveAttribute("text-anchor", "CSS", "text"),
+  text_decoration_line: new NonAdditiveAttribute(
+    "text-decoration-line",
+    "CSS",
+    "text"
+  ),
+  text_rendering: new NonAdditiveAttribute("text-rendering", "CSS", "text"),
+  unicode_bidi: new NonAnimatableAttribute("unicode-bidi", "CSS", "text"),
+  vector_effect: new NonAdditiveAttribute("vector-effect", "CSS", "rect"),
+  visibility: new NonAdditiveAttribute("visibility", "CSS", "rect"),
+  word_spacing: new AdditiveAttribute("word-spacing", "CSS", "text"),
+  writing_mode:
+    // NOTE: Not supported by Mozilla, but explicitly non-animatable
+    new NonAnimatableAttribute("writing-mode", "CSS", "text"),
+};
diff --git a/dom/smil/test/db_smilMappedAttrList.js b/dom/smil/test/db_smilMappedAttrList.js
new file mode 100644
index 0000000000..81f71ef32b
--- /dev/null
+++ b/dom/smil/test/db_smilMappedAttrList.js
@@ -0,0 +1,148 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 sw=2 sts=2 et: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* List of SVG presentational attributes in the SVG 1.1 spec, for use in
+   mochitests. (These are the attributes that are mapped to CSS properties) */
+
+var gMappedAttrList = {
+  // NOTE: The list here should match the MappedAttributeEntry arrays in
+  // SVGElement.cpp
+
+  // PresentationAttributes-FillStroke
+  fill: new AdditiveAttribute("fill", "XML", "rect"),
+  fill_opacity: new AdditiveAttribute("fill-opacity", "XML", "rect"),
+  fill_rule: new NonAdditiveAttribute("fill-rule", "XML", "rect"),
+  stroke: new AdditiveAttribute("stroke", "XML", "rect"),
+  stroke_dasharray: new NonAdditiveAttribute("stroke-dasharray", "XML", "rect"),
+  stroke_dashoffset: new AdditiveAttribute("stroke-dashoffset", "XML", "rect"),
+  stroke_linecap: new NonAdditiveAttribute("stroke-linecap", "XML", "rect"),
+  stroke_linejoin: new NonAdditiveAttribute("stroke-linejoin", "XML", "rect"),
+  stroke_miterlimit: new AdditiveAttribute("stroke-miterlimit", "XML", "rect"),
+  stroke_opacity: new AdditiveAttribute("stroke-opacity", "XML", "rect"),
+  stroke_width: new AdditiveAttribute("stroke-width", "XML", "rect"),
+
+  // PresentationAttributes-Graphics
+  clip_path: new NonAdditiveAttribute("clip-path", "XML", "rect"),
+  clip_rule: new NonAdditiveAttribute("clip-rule", "XML", "circle"),
+  color_interpolation: new NonAdditiveAttribute(
+    "color-interpolation",
+    "XML",
+    "rect"
+  ),
+  cursor: new NonAdditiveAttribute("cursor", "XML", "rect"),
+  display: new NonAdditiveAttribute("display", "XML", "rect"),
+  filter: new NonAdditiveAttribute("filter", "XML", "rect"),
+  image_rendering: NonAdditiveAttribute("image-rendering", "XML", "image"),
+  mask: new NonAdditiveAttribute("mask", "XML", "line"),
+  pointer_events: new NonAdditiveAttribute("pointer-events", "XML", "rect"),
+  shape_rendering: new NonAdditiveAttribute("shape-rendering", "XML", "rect"),
+  text_rendering: new NonAdditiveAttribute("text-rendering", "XML", "text"),
+  visibility: new NonAdditiveAttribute("visibility", "XML", "rect"),
+
+  // PresentationAttributes-TextContentElements
+  // SKIP 'alignment-baseline' property: animatable but not supported by Mozilla
+  // SKIP 'baseline-shift' property: animatable but not supported by Mozilla
+  direction: new NonAnimatableAttribute("direction", "XML", "text"),
+  dominant_baseline: new NonAdditiveAttribute(
+    "dominant-baseline",
+    "XML",
+    "text"
+  ),
+  glyph_orientation_horizontal:
+    // NOTE: Not supported by Mozilla, but explicitly non-animatable
+    NonAnimatableAttribute("glyph-orientation-horizontal", "XML", "text"),
+  glyph_orientation_vertical:
+    // NOTE: Not supported by Mozilla, but explicitly non-animatable
+    NonAnimatableAttribute("glyph-orientation-horizontal", "XML", "text"),
+  // SKIP 'kerning' property: animatable but not supported by Mozilla
+  letter_spacing: new AdditiveAttribute("letter-spacing", "XML", "text"),
+  text_anchor: new NonAdditiveAttribute("text-anchor", "XML", "text"),
+  text_decoration_line: new NonAdditiveAttribute(
+    "text-decoration-line",
+    "XML",
+    "text"
+  ),
+  unicode_bidi: new NonAnimatableAttribute("unicode-bidi", "XML", "text"),
+  word_spacing: new AdditiveAttribute("word-spacing", "XML", "text"),
+
+  // PresentationAttributes-FontSpecification
+  font_family: new NonAdditiveAttribute("font-family", "XML", "text"),
+  font_size: new AdditiveAttribute("font-size", "XML", "text"),
+  font_size_adjust: new NonAdditiveAttribute("font-size-adjust", "XML", "text"),
+  font_stretch: new NonAdditiveAttribute("font-stretch", "XML", "text"),
+  font_style: new NonAdditiveAttribute("font-style", "XML", "text"),
+  font_variant: new NonAdditiveAttribute("font-variant", "XML", "text"),
+  font_weight: new NonAdditiveAttribute("font-weight", "XML", "text"),
+
+  // PresentationAttributes-GradientStop
+  stop_color: new AdditiveAttribute("stop-color", "XML", "stop"),
+  stop_opacity: new AdditiveAttribute("stop-opacity", "XML", "stop"),
+
+  // PresentationAttributes-Viewports
+  overflow: new NonAdditiveAttribute("overflow", "XML", "marker"),
+  clip: new AdditiveAttribute("clip", "XML", "marker"),
+
+  // PresentationAttributes-Makers
+  marker_end: new NonAdditiveAttribute("marker-end", "XML", "line"),
+  marker_mid: new NonAdditiveAttribute("marker-mid", "XML", "line"),
+  marker_start: new NonAdditiveAttribute("marker-start", "XML", "line"),
+
+  // PresentationAttributes-Color
+  color: new AdditiveAttribute("color", "XML", "rect"),
+
+  // PresentationAttributes-Filters
+  color_interpolation_filters: new NonAdditiveAttribute(
+    "color-interpolation-filters",
+    "XML",
+    "feFlood"
+  ),
+
+  // PresentationAttributes-feFlood
+  flood_color: new AdditiveAttribute("flood-color", "XML", "feFlood"),
+  flood_opacity: new AdditiveAttribute("flood-opacity", "XML", "feFlood"),
+
+  // PresentationAttributes-LightingEffects
+  lighting_color: new AdditiveAttribute(
+    "lighting-color",
+    "XML",
+    "feDiffuseLighting"
+  ),
+};
+
+// Utility method to copy a list of TestcaseBundle objects for CSS properties
+// into a list of TestcaseBundles for the corresponding mapped attributes.
+function convertCSSBundlesToMappedAttr(bundleList) {
+  // Create mapping of property names to the corresponding
+  // mapped-attribute object in gMappedAttrList.
+  var propertyNameToMappedAttr = {};
+  for (attributeLabel in gMappedAttrList) {
+    var propName = gMappedAttrList[attributeLabel].attrName;
+    propertyNameToMappedAttr[propName] = gMappedAttrList[attributeLabel];
+  }
+
+  var convertedBundles = [];
+  for (var bundleIdx in bundleList) {
+    var origBundle = bundleList[bundleIdx];
+    var propName = origBundle.animatedAttribute.attrName;
+    if (propertyNameToMappedAttr[propName]) {
+      // There's a mapped attribute by this name! Duplicate the TestcaseBundle,
+      // using the Mapped Attribute instead of the CSS Property.
+      is(
+        origBundle.animatedAttribute.attrType,
+        "CSS",
+        "expecting to be converting from CSS to XML"
+      );
+      convertedBundles.push(
+        new TestcaseBundle(
+          propertyNameToMappedAttr[propName],
+          origBundle.testcaseList,
+          origBundle.skipReason
+        )
+      );
+    }
+  }
+  return convertedBundles;
+}
diff --git a/dom/smil/test/file_smilWithTransition.html b/dom/smil/test/file_smilWithTransition.html
new file mode 100644
index 0000000000..b91398436b
--- /dev/null
+++ b/dom/smil/test/file_smilWithTransition.html
@@ -0,0 +1,79 @@
+<!doctype html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1315874
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test SMIL does not trigger CSS Transitions (bug 1315874)</title>
+</head>
+<body>
+<a target="_blank"
+  href="https://bugzilla.mozilla.org/show_bug.cgi?id=1315874">Mozilla Bug
+  1315874</a>
+<svg>
+  <rect width="100%" height="100%"
+        style="fill: red; transition: fill 10s" id="rect">
+    <animate attributeName="fill" to="lime" dur="1s" fill="freeze">
+  </rect>
+</svg>
+<script  type="text/javascript">
+  // Bring SimpleTest's function from opener.
+  if (opener) {
+    var is = opener.is.bind(opener);
+    var ok = opener.ok.bind(opener);
+    function finish() {
+      var o = opener;
+      self.close();
+      o.SimpleTest.finish();
+    }
+  }
+
+  window.addEventListener('load', runTests);
+
+  var rect = document.getElementById('rect');
+  var svg = document.getElementsByTagName('svg')[0];
+  is(getComputedStyle(rect).fill, 'rgb(255, 0, 0)',
+     'The initial color should be red.');
+
+  function runTests() {
+    waitForFrame().then(function() {
+      svg.setCurrentTime(1);
+      is(getComputedStyle(rect).fill, 'rgb(0, 255, 0)',
+         'The end color should be lime.');
+
+      return waitForAnimationFrames(2);
+    }).then(function() {
+      var anim = document.getAnimations()[0];
+      ok(!anim, 'Transition should not be created by restyling for SMIL');
+      finish();
+    });
+  }
+
+  // Utility methods from testcommon.js
+  // For detail, see dom/animation/test/testcommon.js.
+
+  function waitForFrame() {
+    return new Promise(function(resolve, reject) {
+      requestAnimationFrame(function(time) {
+        resolve();
+      });
+    });
+  }
+
+  function waitForAnimationFrames(frameCount) {
+    return new Promise(function(resolve, reject) {
+      function handleFrame() {
+        if (--frameCount <= 0) {
+          resolve();
+        } else {
+          window.requestAnimationFrame(handleFrame);
+        }
+      }
+      window.requestAnimationFrame(handleFrame);
+    });
+  }
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/mochitest.toml b/dom/smil/test/mochitest.toml
new file mode 100644
index 0000000000..7a3e98fa57
--- /dev/null
+++ b/dom/smil/test/mochitest.toml
@@ -0,0 +1,109 @@
+[DEFAULT]
+support-files = [
+  "db_smilAnimateMotion.js",
+  "db_smilCSSFromBy.js",
+  "db_smilCSSFromTo.js",
+  "db_smilCSSPaced.js",
+  "db_smilCSSPropertyList.js",
+  "db_smilMappedAttrList.js",
+  "file_smilWithTransition.html",
+  "smilAnimateMotionValueLists.js",
+  "smilExtDoc_helper.svg",
+  "smilTestUtils.js",
+  "smilXHR_helper.svg",
+]
+
+["test_smilAccessKey.xhtml"]
+
+["test_smilAdditionFallback.html"]
+
+["test_smilAnimateMotion.xhtml"]
+
+["test_smilAnimateMotionInvalidValues.xhtml"]
+
+["test_smilAnimateMotionOverrideRules.xhtml"]
+
+["test_smilBackwardsSeeking.xhtml"]
+
+["test_smilCSSFontStretchRelative.xhtml"]
+
+["test_smilCSSFromBy.xhtml"]
+
+["test_smilCSSFromTo.xhtml"]
+
+["test_smilCSSInherit.xhtml"]
+disabled = "until bug 501183 is fixed"
+
+["test_smilCSSInvalidValues.xhtml"]
+
+["test_smilCSSPaced.xhtml"]
+
+["test_smilChangeAfterFrozen.xhtml"]
+skip-if = ["true"] # bug 1358955.
+
+["test_smilConditionalProcessing.html"]
+
+["test_smilContainerBinding.xhtml"]
+
+["test_smilCrossContainer.xhtml"]
+
+["test_smilDynamicDelayedBeginElement.xhtml"]
+
+["test_smilExtDoc.xhtml"]
+
+["test_smilFillMode.xhtml"]
+
+["test_smilGetSimpleDuration.xhtml"]
+
+["test_smilGetStartTime.xhtml"]
+
+["test_smilHyperlinking.xhtml"]
+
+["test_smilInvalidValues.html"]
+
+["test_smilKeySplines.xhtml"]
+
+["test_smilKeyTimes.xhtml"]
+
+["test_smilKeyTimesPacedMode.xhtml"]
+
+["test_smilMappedAttrFromBy.xhtml"]
+
+["test_smilMappedAttrFromTo.xhtml"]
+
+["test_smilMappedAttrPaced.xhtml"]
+
+["test_smilMinTiming.html"]
+
+["test_smilRepeatDuration.html"]
+
+["test_smilRepeatTiming.xhtml"]
+
+["test_smilReset.xhtml"]
+
+["test_smilRestart.xhtml"]
+
+["test_smilSetCurrentTime.xhtml"]
+
+["test_smilSync.xhtml"]
+
+["test_smilSyncTransform.xhtml"]
+
+["test_smilSyncbaseTarget.xhtml"]
+
+["test_smilTextZoom.xhtml"]
+
+["test_smilTiming.xhtml"]
+
+["test_smilTimingZeroIntervals.xhtml"]
+
+["test_smilUpdatedInterval.xhtml"]
+
+["test_smilValues.xhtml"]
+
+["test_smilWithTransition.html"]
+skip-if = ["os == 'android'"]
+
+["test_smilWithXlink.xhtml"]
+
+["test_smilXHR.xhtml"]
diff --git a/dom/smil/test/smilAnimateMotionValueLists.js b/dom/smil/test/smilAnimateMotionValueLists.js
new file mode 100644
index 0000000000..6e05ebd7e1
--- /dev/null
+++ b/dom/smil/test/smilAnimateMotionValueLists.js
@@ -0,0 +1,116 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 sw=2 sts=2 et: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Lists of valid & invalid values for the various <animateMotion> attributes */
+const gValidValues = [
+  "10 10",
+  "10 10;", // Trailing semicolons are allowed
+  "10 10;  ",
+  "   10   10em  ",
+  "1 2  ; 3,4",
+  "1,2;3,4",
+  "0 0",
+  "0,0",
+];
+
+const gInvalidValues = [
+  ";10 10",
+  "10 10;;",
+  "1 2 3",
+  "1 2 3 4",
+  "1,2;3,4 ,",
+  ",",
+  " , ",
+  ";",
+  " ; ",
+  "a",
+  " a; ",
+  ";a;",
+  "",
+  " ",
+  "1,2;3,4,",
+  "1,,2",
+  ",1,2",
+];
+
+const gValidRotate = [
+  "10",
+  "20.1",
+  "30.5deg",
+  "0.5rad",
+  "auto",
+  "auto-reverse",
+  " 10 ",
+  "  10deg",
+  "10deg ",
+  " 10.1 ",
+];
+
+const gInvalidRotate = ["10 deg", "10 rad    ", "aaa"];
+
+const gValidToBy = ["0 0", "1em,2", "50.3em 0.2in", " 1,2", "1 2 "];
+
+const gInvalidToBy = [
+  "0 0 0",
+  "0 0,0",
+  "0,0,0",
+  "1emm 2",
+  "1 2;",
+  "1 2,",
+  " 1,2 ,",
+  "abc",
+  ",",
+  "",
+  "1,,2",
+  "1,2,",
+];
+
+const gValidPath = [
+  "m0 0     L30 30",
+  "M20,20L10    10",
+  "M20,20 L30, 30h20",
+  "m50 50",
+  "M50 50",
+  "m0 0",
+  "M0, 0",
+];
+
+// paths must start with at least a valid "M" segment to be valid
+const gInvalidPath = ["M20in 20", "h30", "L50 50", "abc"];
+
+// paths that at least start with a valid "M" segment are valid - the spec says
+// to parse everything up to the first invalid token
+const gValidPathWithErrors = ["M20 20em", "m0 0 L30,,30", "M10 10 L50 50 abc"];
+
+const gValidKeyPoints = [
+  "0; 0.5; 1",
+  "0;.5;1",
+  "0; 0; 1",
+  "0; 1; 1",
+  "0; 0; 1;", // Trailing semicolons are allowed
+  "0; 0; 1; ",
+  "0; 0.000; 1",
+  "0; 0.000001; 1",
+];
+
+// Should have 3 values to be valid.
+// Same as number of keyTimes values
+const gInvalidKeyPoints = [
+  "0; 1",
+  "0; 0.5; 0.75; 1",
+  "0; 1;",
+  "0",
+  "1",
+  "a",
+  "",
+  "  ",
+  "0; -0.1; 1",
+  "0; 1.1; 1",
+  "0; 0.1; 1.1",
+  "-0.1; 0.1; 1",
+  "0; a; 1",
+  "0;;1",
+];
diff --git a/dom/smil/test/smilExtDoc_helper.svg b/dom/smil/test/smilExtDoc_helper.svg
new file mode 100644
index 0000000000..fbd9d091a4
--- /dev/null
+++ b/dom/smil/test/smilExtDoc_helper.svg
@@ -0,0 +1,7 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+  <filter id="filter">
+    <feFlood flood-color="red">
+      <set attributeName="flood-color" to="lime" begin="0.001"/>
+    </feFlood>
+  </filter>
+</svg>
diff --git a/dom/smil/test/smilTestUtils.js b/dom/smil/test/smilTestUtils.js
new file mode 100644
index 0000000000..be270a39bf
--- /dev/null
+++ b/dom/smil/test/smilTestUtils.js
@@ -0,0 +1,1015 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 sw=2 sts=2 et: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Note: Class syntax roughly based on:
+// https://developer.mozilla.org/en/Core_JavaScript_1.5_Guide/Inheritance
+const SVG_NS = "http://www.w3.org/2000/svg";
+const XLINK_NS = "http://www.w3.org/1999/xlink";
+
+const MPATH_TARGET_ID = "smilTestUtilsTestingPath";
+
+function extend(child, supertype) {
+  child.prototype.__proto__ = supertype.prototype;
+}
+
+// General Utility Methods
+var SMILUtil = {
+  // Returns the first matched <svg> node in the document
+  getSVGRoot() {
+    return SMILUtil.getFirstElemWithTag("svg");
+  },
+
+  // Returns the first element in the document with the matching tag
+  getFirstElemWithTag(aTargetTag) {
+    var elemList = document.getElementsByTagName(aTargetTag);
+    return !elemList.length ? null : elemList[0];
+  },
+
+  // Simple wrapper for getComputedStyle
+  getComputedStyleSimple(elem, prop) {
+    return window.getComputedStyle(elem).getPropertyValue(prop);
+  },
+
+  getAttributeValue(elem, attr) {
+    if (attr.attrName == SMILUtil.getMotionFakeAttributeName()) {
+      // Fake motion "attribute" -- "computed value" is the element's CTM
+      return elem.getCTM();
+    }
+    if (attr.attrType == "CSS") {
+      return SMILUtil.getComputedStyleWrapper(elem, attr.attrName);
+    }
+    if (attr.attrType == "XML") {
+      // XXXdholbert This is appropriate for mapped attributes, but not
+      // for other attributes.
+      return SMILUtil.getComputedStyleWrapper(elem, attr.attrName);
+    }
+    throw new Error(`Unexpected attribute value ${attr.attrType}`);
+  },
+
+  // Smart wrapper for getComputedStyle, which will generate a "fake" computed
+  // style for recognized shorthand properties (font, font-variant, overflow, marker)
+  getComputedStyleWrapper(elem, propName) {
+    // Special cases for shorthand properties (which aren't directly queriable
+    // via getComputedStyle)
+    var computedStyle;
+    if (propName == "font") {
+      var subProps = [
+        "font-style",
+        "font-variant-caps",
+        "font-weight",
+        "font-size",
+        "line-height",
+        "font-family",
+      ];
+      for (var i in subProps) {
+        var subPropStyle = SMILUtil.getComputedStyleSimple(elem, subProps[i]);
+        if (subPropStyle) {
+          if (subProps[i] == "line-height") {
+            // There needs to be a "/" before line-height
+            subPropStyle = "/ " + subPropStyle;
+          }
+          if (!computedStyle) {
+            computedStyle = subPropStyle;
+          } else {
+            computedStyle = computedStyle + " " + subPropStyle;
+          }
+        }
+      }
+    } else if (propName == "font-variant") {
+      // xxx - this isn't completely correct but it's sufficient for what's
+      //       being tested here
+      computedStyle = SMILUtil.getComputedStyleSimple(
+        elem,
+        "font-variant-caps"
+      );
+    } else if (propName == "marker") {
+      var subProps = ["marker-end", "marker-mid", "marker-start"];
+      for (var i in subProps) {
+        if (!computedStyle) {
+          computedStyle = SMILUtil.getComputedStyleSimple(elem, subProps[i]);
+        } else {
+          is(
+            computedStyle,
+            SMILUtil.getComputedStyleSimple(elem, subProps[i]),
+            "marker sub-properties should match each other " +
+              "(they shouldn't be individually set)"
+          );
+        }
+      }
+    } else if (propName == "overflow") {
+      var subProps = ["overflow-x", "overflow-y"];
+      for (var i in subProps) {
+        if (!computedStyle) {
+          computedStyle = SMILUtil.getComputedStyleSimple(elem, subProps[i]);
+        } else {
+          is(
+            computedStyle,
+            SMILUtil.getComputedStyleSimple(elem, subProps[i]),
+            "overflow sub-properties should match each other " +
+              "(they shouldn't be individually set)"
+          );
+        }
+      }
+    } else {
+      computedStyle = SMILUtil.getComputedStyleSimple(elem, propName);
+    }
+    return computedStyle;
+  },
+
+  getMotionFakeAttributeName() {
+    return "_motion";
+  },
+
+  // Return stripped px value from specified value.
+  stripPx: str => str.replace(/px\s*$/, ""),
+};
+
+var CTMUtil = {
+  CTM_COMPONENTS_ALL: ["a", "b", "c", "d", "e", "f"],
+  CTM_COMPONENTS_ROTATE: ["a", "b", "c", "d"],
+
+  // Function to generate a CTM Matrix from a "summary"
+  // (a 3-tuple containing [tX, tY, theta])
+  generateCTM(aCtmSummary) {
+    if (!aCtmSummary || aCtmSummary.length != 3) {
+      ok(false, "Unexpected CTM summary tuple length: " + aCtmSummary.length);
+    }
+    var tX = aCtmSummary[0];
+    var tY = aCtmSummary[1];
+    var theta = aCtmSummary[2];
+    var cosTheta = Math.cos(theta);
+    var sinTheta = Math.sin(theta);
+    var newCtm = {
+      a: cosTheta,
+      c: -sinTheta,
+      e: tX,
+      b: sinTheta,
+      d: cosTheta,
+      f: tY,
+    };
+    return newCtm;
+  },
+
+  /// Helper for isCtmEqual
+  isWithinDelta(aTestVal, aExpectedVal, aErrMsg, aIsTodo) {
+    var testFunc = aIsTodo ? todo : ok;
+    const delta = 0.00001; // allowing margin of error = 10^-5
+    ok(
+      aTestVal >= aExpectedVal - delta && aTestVal <= aExpectedVal + delta,
+      aErrMsg + " | got: " + aTestVal + ", expected: " + aExpectedVal
+    );
+  },
+
+  assertCTMEqual(aLeftCtm, aRightCtm, aComponentsToCheck, aErrMsg, aIsTodo) {
+    var foundCTMDifference = false;
+    for (var j in aComponentsToCheck) {
+      var curComponent = aComponentsToCheck[j];
+      if (!aIsTodo) {
+        CTMUtil.isWithinDelta(
+          aLeftCtm[curComponent],
+          aRightCtm[curComponent],
+          aErrMsg + " | component: " + curComponent,
+          false
+        );
+      } else if (aLeftCtm[curComponent] != aRightCtm[curComponent]) {
+        foundCTMDifference = true;
+      }
+    }
+
+    if (aIsTodo) {
+      todo(!foundCTMDifference, aErrMsg + " | (currently marked todo)");
+    }
+  },
+
+  assertCTMNotEqual(aLeftCtm, aRightCtm, aComponentsToCheck, aErrMsg, aIsTodo) {
+    // CTM should not match initial one
+    var foundCTMDifference = false;
+    for (var j in aComponentsToCheck) {
+      var curComponent = aComponentsToCheck[j];
+      if (aLeftCtm[curComponent] != aRightCtm[curComponent]) {
+        foundCTMDifference = true;
+        break; // We found a difference, as expected. Success!
+      }
+    }
+
+    if (aIsTodo) {
+      todo(foundCTMDifference, aErrMsg + " | (currently marked todo)");
+    } else {
+      ok(foundCTMDifference, aErrMsg);
+    }
+  },
+};
+
+// Wrapper for timing information
+function SMILTimingData(aBegin, aDur) {
+  this._begin = aBegin;
+  this._dur = aDur;
+}
+SMILTimingData.prototype = {
+  _begin: null,
+  _dur: null,
+  getBeginTime() {
+    return this._begin;
+  },
+  getDur() {
+    return this._dur;
+  },
+  getEndTime() {
+    return this._begin + this._dur;
+  },
+  getFractionalTime(aPortion) {
+    return this._begin + aPortion * this._dur;
+  },
+};
+
+/**
+ * Attribute: a container for information about an attribute we'll
+ * attempt to animate with SMIL in our tests.
+ *
+ * See also the factory methods below: NonAnimatableAttribute(),
+ * NonAdditiveAttribute(), and AdditiveAttribute().
+ *
+ * @param aAttrName The name of the attribute
+ * @param aAttrType The type of the attribute ("CSS" vs "XML")
+ * @param aTargetTag The name of an element that this attribute could be
+ *                   applied to.
+ * @param aIsAnimatable A bool indicating whether this attribute is defined as
+ *                      animatable in the SVG spec.
+ * @param aIsAdditive   A bool indicating whether this attribute is defined as
+ *                      additive (i.e. supports "by" animation) in the SVG spec.
+ */
+function Attribute(
+  aAttrName,
+  aAttrType,
+  aTargetTag,
+  aIsAnimatable,
+  aIsAdditive
+) {
+  this.attrName = aAttrName;
+  this.attrType = aAttrType;
+  this.targetTag = aTargetTag;
+  this.isAnimatable = aIsAnimatable;
+  this.isAdditive = aIsAdditive;
+}
+Attribute.prototype = {
+  // Member variables
+  attrName: null,
+  attrType: null,
+  isAnimatable: null,
+  testcaseList: null,
+};
+
+// Generators for Attribute objects.  These allow lists of attribute
+// definitions to be more human-readible than if we were using Attribute() with
+// boolean flags, e.g. "Attribute(..., true, true), Attribute(..., true, false)
+function NonAnimatableAttribute(aAttrName, aAttrType, aTargetTag) {
+  return new Attribute(aAttrName, aAttrType, aTargetTag, false, false);
+}
+function NonAdditiveAttribute(aAttrName, aAttrType, aTargetTag) {
+  return new Attribute(aAttrName, aAttrType, aTargetTag, true, false);
+}
+function AdditiveAttribute(aAttrName, aAttrType, aTargetTag) {
+  return new Attribute(aAttrName, aAttrType, aTargetTag, true, true);
+}
+
+/**
+ * TestcaseBundle: a container for a group of tests for a particular attribute
+ *
+ * @param aAttribute An Attribute object for the attribute
+ * @param aTestcaseList An array of AnimTestcase objects
+ */
+function TestcaseBundle(aAttribute, aTestcaseList, aSkipReason) {
+  this.animatedAttribute = aAttribute;
+  this.testcaseList = aTestcaseList;
+  this.skipReason = aSkipReason;
+}
+TestcaseBundle.prototype = {
+  // Member variables
+  animatedAttribute: null,
+  testcaseList: null,
+  skipReason: null,
+
+  // Methods
+  go(aTimingData) {
+    if (this.skipReason) {
+      todo(
+        false,
+        "Skipping a bundle for '" +
+          this.animatedAttribute.attrName +
+          "' because: " +
+          this.skipReason
+      );
+    } else {
+      // Sanity Check: Bundle should have > 0 testcases
+      if (!this.testcaseList || !this.testcaseList.length) {
+        ok(
+          false,
+          "a bundle for '" +
+            this.animatedAttribute.attrName +
+            "' has no testcases"
+        );
+      }
+
+      var targetElem = SMILUtil.getFirstElemWithTag(
+        this.animatedAttribute.targetTag
+      );
+
+      if (!targetElem) {
+        ok(
+          false,
+          "Error: can't find an element of type '" +
+            this.animatedAttribute.targetTag +
+            "', so I can't test property '" +
+            this.animatedAttribute.attrName +
+            "'"
+        );
+        return;
+      }
+
+      for (var testcaseIdx in this.testcaseList) {
+        var testcase = this.testcaseList[testcaseIdx];
+        if (testcase.skipReason) {
+          todo(
+            false,
+            "Skipping a testcase for '" +
+              this.animatedAttribute.attrName +
+              "' because: " +
+              testcase.skipReason
+          );
+        } else {
+          testcase.runTest(
+            targetElem,
+            this.animatedAttribute,
+            aTimingData,
+            false
+          );
+          testcase.runTest(
+            targetElem,
+            this.animatedAttribute,
+            aTimingData,
+            true
+          );
+        }
+      }
+    }
+  },
+};
+
+/**
+ * AnimTestcase: an abstract class that represents an animation testcase.
+ * (e.g. a set of "from"/"to" values to test)
+ */
+function AnimTestcase() {} // abstract => no constructor
+AnimTestcase.prototype = {
+  // Member variables
+  _animElementTagName: "animate", // Can be overridden for e.g. animateColor
+  computedValMap: null,
+  skipReason: null,
+
+  // Methods
+  /**
+   * runTest: Runs this AnimTestcase
+   *
+   * @param aTargetElem The node to be targeted in our test animation.
+   * @param aTargetAttr An Attribute object representing the attribute
+   *                    to be targeted in our test animation.
+   * @param aTimeData A SMILTimingData object with timing information for
+   *                  our test animation.
+   * @param aIsFreeze If true, indicates that our test animation should use
+   *                  fill="freeze"; otherwise, we'll default to fill="remove".
+   */
+  runTest(aTargetElem, aTargetAttr, aTimeData, aIsFreeze) {
+    // SANITY CHECKS
+    if (!SMILUtil.getSVGRoot().animationsPaused()) {
+      ok(false, "Should start each test with animations paused");
+    }
+    if (SMILUtil.getSVGRoot().getCurrentTime() != 0) {
+      ok(false, "Should start each test at time = 0");
+    }
+
+    // SET UP
+    // Cache initial computed value
+    var baseVal = SMILUtil.getAttributeValue(aTargetElem, aTargetAttr);
+
+    // Create & append animation element
+    var anim = this.setupAnimationElement(aTargetAttr, aTimeData, aIsFreeze);
+    aTargetElem.appendChild(anim);
+
+    // Build a list of [seek-time, expectedValue, errorMessage] triplets
+    var seekList = this.buildSeekList(
+      aTargetAttr,
+      baseVal,
+      aTimeData,
+      aIsFreeze
+    );
+
+    // DO THE ACTUAL TESTING
+    this.seekAndTest(seekList, aTargetElem, aTargetAttr);
+
+    // CLEAN UP
+    aTargetElem.removeChild(anim);
+    SMILUtil.getSVGRoot().setCurrentTime(0);
+  },
+
+  // HELPER FUNCTIONS
+  // setupAnimationElement: <animate> element
+  // Subclasses should extend this parent method
+  setupAnimationElement(aAnimAttr, aTimeData, aIsFreeze) {
+    var animElement = document.createElementNS(
+      SVG_NS,
+      this._animElementTagName
+    );
+    animElement.setAttribute("attributeName", aAnimAttr.attrName);
+    animElement.setAttribute("attributeType", aAnimAttr.attrType);
+    animElement.setAttribute("begin", aTimeData.getBeginTime());
+    animElement.setAttribute("dur", aTimeData.getDur());
+    if (aIsFreeze) {
+      animElement.setAttribute("fill", "freeze");
+    }
+    return animElement;
+  },
+
+  buildSeekList(aAnimAttr, aBaseVal, aTimeData, aIsFreeze) {
+    if (!aAnimAttr.isAnimatable) {
+      return this.buildSeekListStatic(
+        aAnimAttr,
+        aBaseVal,
+        aTimeData,
+        "defined as non-animatable in SVG spec"
+      );
+    }
+    if (this.computedValMap.noEffect) {
+      return this.buildSeekListStatic(
+        aAnimAttr,
+        aBaseVal,
+        aTimeData,
+        "testcase specified to have no effect"
+      );
+    }
+    return this.buildSeekListAnimated(
+      aAnimAttr,
+      aBaseVal,
+      aTimeData,
+      aIsFreeze
+    );
+  },
+
+  seekAndTest(aSeekList, aTargetElem, aTargetAttr) {
+    var svg = document.getElementById("svg");
+    for (var i in aSeekList) {
+      var entry = aSeekList[i];
+      SMILUtil.getSVGRoot().setCurrentTime(entry[0]);
+
+      // Bug 1379908: The computed value of stroke-* properties should be
+      // serialized with px units, but currently Gecko and Servo don't do that
+      // when animating these values.
+      if (
+        ["stroke-width", "stroke-dasharray", "stroke-dashoffset"].includes(
+          aTargetAttr.attrName
+        )
+      ) {
+        var attr = SMILUtil.stripPx(
+          SMILUtil.getAttributeValue(aTargetElem, aTargetAttr)
+        );
+        var expectedVal = SMILUtil.stripPx(entry[1]);
+        is(attr, expectedVal, entry[2]);
+        return;
+      }
+      is(
+        SMILUtil.getAttributeValue(aTargetElem, aTargetAttr),
+        entry[1],
+        entry[2]
+      );
+    }
+  },
+
+  // methods that expect to be overridden in subclasses
+  buildSeekListStatic(aAnimAttr, aBaseVal, aTimeData, aReasonStatic) {},
+  buildSeekListAnimated(aAnimAttr, aBaseVal, aTimeData, aIsFreeze) {},
+};
+
+// Abstract parent class to share code between from-to & from-by testcases.
+function AnimTestcaseFrom() {} // abstract => no constructor
+AnimTestcaseFrom.prototype = {
+  // Member variables
+  from: null,
+
+  // Methods
+  setupAnimationElement(aAnimAttr, aTimeData, aIsFreeze) {
+    // Call super, and then add my own customization
+    var animElem = AnimTestcase.prototype.setupAnimationElement.apply(this, [
+      aAnimAttr,
+      aTimeData,
+      aIsFreeze,
+    ]);
+    animElem.setAttribute("from", this.from);
+    return animElem;
+  },
+
+  buildSeekListStatic(aAnimAttr, aBaseVal, aTimeData, aReasonStatic) {
+    var seekList = new Array();
+    var msgPrefix =
+      aAnimAttr.attrName + ": shouldn't be affected by animation ";
+    seekList.push([
+      aTimeData.getBeginTime(),
+      aBaseVal,
+      msgPrefix + "(at animation begin) - " + aReasonStatic,
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(1 / 2),
+      aBaseVal,
+      msgPrefix + "(at animation mid) - " + aReasonStatic,
+    ]);
+    seekList.push([
+      aTimeData.getEndTime(),
+      aBaseVal,
+      msgPrefix + "(at animation end) - " + aReasonStatic,
+    ]);
+    seekList.push([
+      aTimeData.getEndTime() + aTimeData.getDur(),
+      aBaseVal,
+      msgPrefix + "(after animation end) - " + aReasonStatic,
+    ]);
+    return seekList;
+  },
+
+  buildSeekListAnimated(aAnimAttr, aBaseVal, aTimeData, aIsFreeze) {
+    var seekList = new Array();
+    var msgPrefix = aAnimAttr.attrName + ": ";
+    if (aTimeData.getBeginTime() > 0.1) {
+      seekList.push([
+        aTimeData.getBeginTime() - 0.1,
+        aBaseVal,
+        msgPrefix +
+          "checking that base value is set " +
+          "before start of animation",
+      ]);
+    }
+
+    seekList.push([
+      aTimeData.getBeginTime(),
+      this.computedValMap.fromComp || this.from,
+      msgPrefix +
+        "checking that 'from' value is set " +
+        "at start of animation",
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(1 / 2),
+      this.computedValMap.midComp || this.computedValMap.toComp || this.to,
+      msgPrefix + "checking value halfway through animation",
+    ]);
+
+    var finalMsg;
+    var expectedEndVal;
+    if (aIsFreeze) {
+      expectedEndVal = this.computedValMap.toComp || this.to;
+      finalMsg = msgPrefix + "[freeze-mode] checking that final value is set ";
+    } else {
+      expectedEndVal = aBaseVal;
+      finalMsg =
+        msgPrefix + "[remove-mode] checking that animation is cleared ";
+    }
+    seekList.push([
+      aTimeData.getEndTime(),
+      expectedEndVal,
+      finalMsg + "at end of animation",
+    ]);
+    seekList.push([
+      aTimeData.getEndTime() + aTimeData.getDur(),
+      expectedEndVal,
+      finalMsg + "after end of animation",
+    ]);
+    return seekList;
+  },
+};
+extend(AnimTestcaseFrom, AnimTestcase);
+
+/*
+ * A testcase for a simple "from-to" animation
+ * @param aFrom  The 'from' value
+ * @param aTo    The 'to' value
+ * @param aComputedValMap  A hash-map that contains some computed values,
+ *                         if they're needed, as follows:
+ *    - fromComp: Computed value version of |aFrom| (if different from |aFrom|)
+ *    - midComp:  Computed value that we expect to visit halfway through the
+ *                animation (if different from |aTo|)
+ *    - toComp:   Computed value version of |aTo| (if different from |aTo|)
+ *    - noEffect: Special flag -- if set, indicates that this testcase is
+ *                expected to have no effect on the computed value. (e.g. the
+ *                given values are invalid.)
+ * @param aSkipReason  If this test-case is known to currently fail, this
+ *                     parameter should be a string explaining why.
+ *                     Otherwise, this value should be null (or omitted).
+ *
+ */
+function AnimTestcaseFromTo(aFrom, aTo, aComputedValMap, aSkipReason) {
+  this.from = aFrom;
+  this.to = aTo;
+  this.computedValMap = aComputedValMap || {}; // Let aComputedValMap be omitted
+  this.skipReason = aSkipReason;
+}
+AnimTestcaseFromTo.prototype = {
+  // Member variables
+  to: null,
+
+  // Methods
+  setupAnimationElement(aAnimAttr, aTimeData, aIsFreeze) {
+    // Call super, and then add my own customization
+    var animElem = AnimTestcaseFrom.prototype.setupAnimationElement.apply(
+      this,
+      [aAnimAttr, aTimeData, aIsFreeze]
+    );
+    animElem.setAttribute("to", this.to);
+    return animElem;
+  },
+};
+extend(AnimTestcaseFromTo, AnimTestcaseFrom);
+
+/*
+ * A testcase for a simple "from-by" animation.
+ *
+ * @param aFrom  The 'from' value
+ * @param aBy    The 'by' value
+ * @param aComputedValMap  A hash-map that contains some computed values that
+ *                         we expect to visit, as follows:
+ *    - fromComp: Computed value version of |aFrom| (if different from |aFrom|)
+ *    - midComp:  Computed value that we expect to visit halfway through the
+ *                animation (|aFrom| + |aBy|/2)
+ *    - toComp:   Computed value of the animation endpoint (|aFrom| + |aBy|)
+ *    - noEffect: Special flag -- if set, indicates that this testcase is
+ *                expected to have no effect on the computed value. (e.g. the
+ *                given values are invalid.  Or the attribute may be animatable
+ *                and additive, but the particular "from" & "by" values that
+ *                are used don't support addition.)
+ * @param aSkipReason  If this test-case is known to currently fail, this
+ *                     parameter should be a string explaining why.
+ *                     Otherwise, this value should be null (or omitted).
+ */
+function AnimTestcaseFromBy(aFrom, aBy, aComputedValMap, aSkipReason) {
+  this.from = aFrom;
+  this.by = aBy;
+  this.computedValMap = aComputedValMap;
+  this.skipReason = aSkipReason;
+  if (
+    this.computedValMap &&
+    !this.computedValMap.noEffect &&
+    !this.computedValMap.toComp
+  ) {
+    ok(false, "AnimTestcaseFromBy needs expected computed final value");
+  }
+}
+AnimTestcaseFromBy.prototype = {
+  // Member variables
+  by: null,
+
+  // Methods
+  setupAnimationElement(aAnimAttr, aTimeData, aIsFreeze) {
+    // Call super, and then add my own customization
+    var animElem = AnimTestcaseFrom.prototype.setupAnimationElement.apply(
+      this,
+      [aAnimAttr, aTimeData, aIsFreeze]
+    );
+    animElem.setAttribute("by", this.by);
+    return animElem;
+  },
+  buildSeekList(aAnimAttr, aBaseVal, aTimeData, aIsFreeze) {
+    if (!aAnimAttr.isAdditive) {
+      return this.buildSeekListStatic(
+        aAnimAttr,
+        aBaseVal,
+        aTimeData,
+        "defined as non-additive in SVG spec"
+      );
+    }
+    // Just use inherited method
+    return AnimTestcaseFrom.prototype.buildSeekList.apply(this, [
+      aAnimAttr,
+      aBaseVal,
+      aTimeData,
+      aIsFreeze,
+    ]);
+  },
+};
+extend(AnimTestcaseFromBy, AnimTestcaseFrom);
+
+/*
+ * A testcase for a "paced-mode" animation
+ * @param aValues   An array of values, to be used as the "Values" list
+ * @param aComputedValMap  A hash-map that contains some computed values,
+ *                         if they're needed, as follows:
+ *      - comp0:   The computed value at the start of the animation
+ *      - comp1_6: The computed value exactly 1/6 through animation
+ *      - comp1_3: The computed value exactly 1/3 through animation
+ *      - comp2_3: The computed value exactly 2/3 through animation
+ *      - comp1:   The computed value of the animation endpoint
+ *  The math works out easiest if...
+ *    (a) aValuesString has 3 entries in its values list: vA, vB, vC
+ *    (b) dist(vB, vC) = 2 * dist(vA, vB)
+ *  With this setup, we can come up with expected intermediate values according
+ *  to the following rules:
+ *    - comp0 should be vA
+ *    - comp1_6 should be us halfway between vA and vB
+ *    - comp1_3 should be vB
+ *    - comp2_3 should be halfway between vB and vC
+ *    - comp1 should be vC
+ * @param aSkipReason  If this test-case is known to currently fail, this
+ *                     parameter should be a string explaining why.
+ *                     Otherwise, this value should be null (or omitted).
+ */
+function AnimTestcasePaced(aValuesString, aComputedValMap, aSkipReason) {
+  this.valuesString = aValuesString;
+  this.computedValMap = aComputedValMap;
+  this.skipReason = aSkipReason;
+  if (
+    this.computedValMap &&
+    (!this.computedValMap.comp0 ||
+      !this.computedValMap.comp1_6 ||
+      !this.computedValMap.comp1_3 ||
+      !this.computedValMap.comp2_3 ||
+      !this.computedValMap.comp1)
+  ) {
+    ok(false, "This AnimTestcasePaced has an incomplete computed value map");
+  }
+}
+AnimTestcasePaced.prototype = {
+  // Member variables
+  valuesString: null,
+
+  // Methods
+  setupAnimationElement(aAnimAttr, aTimeData, aIsFreeze) {
+    // Call super, and then add my own customization
+    var animElem = AnimTestcase.prototype.setupAnimationElement.apply(this, [
+      aAnimAttr,
+      aTimeData,
+      aIsFreeze,
+    ]);
+    animElem.setAttribute("values", this.valuesString);
+    animElem.setAttribute("calcMode", "paced");
+    return animElem;
+  },
+  buildSeekListAnimated(aAnimAttr, aBaseVal, aTimeData, aIsFreeze) {
+    var seekList = new Array();
+    var msgPrefix = aAnimAttr.attrName + ": checking value ";
+    seekList.push([
+      aTimeData.getBeginTime(),
+      this.computedValMap.comp0,
+      msgPrefix + "at start of animation",
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(1 / 6),
+      this.computedValMap.comp1_6,
+      msgPrefix + "1/6 of the way through animation.",
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(1 / 3),
+      this.computedValMap.comp1_3,
+      msgPrefix + "1/3 of the way through animation.",
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(2 / 3),
+      this.computedValMap.comp2_3,
+      msgPrefix + "2/3 of the way through animation.",
+    ]);
+
+    var finalMsg;
+    var expectedEndVal;
+    if (aIsFreeze) {
+      expectedEndVal = this.computedValMap.comp1;
+      finalMsg =
+        aAnimAttr.attrName +
+        ": [freeze-mode] checking that final value is set ";
+    } else {
+      expectedEndVal = aBaseVal;
+      finalMsg =
+        aAnimAttr.attrName +
+        ": [remove-mode] checking that animation is cleared ";
+    }
+    seekList.push([
+      aTimeData.getEndTime(),
+      expectedEndVal,
+      finalMsg + "at end of animation",
+    ]);
+    seekList.push([
+      aTimeData.getEndTime() + aTimeData.getDur(),
+      expectedEndVal,
+      finalMsg + "after end of animation",
+    ]);
+    return seekList;
+  },
+  buildSeekListStatic(aAnimAttr, aBaseVal, aTimeData, aReasonStatic) {
+    var seekList = new Array();
+    var msgPrefix =
+      aAnimAttr.attrName + ": shouldn't be affected by animation ";
+    seekList.push([
+      aTimeData.getBeginTime(),
+      aBaseVal,
+      msgPrefix + "(at animation begin) - " + aReasonStatic,
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(1 / 6),
+      aBaseVal,
+      msgPrefix + "(1/6 of the way through animation) - " + aReasonStatic,
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(1 / 3),
+      aBaseVal,
+      msgPrefix + "(1/3 of the way through animation) - " + aReasonStatic,
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(2 / 3),
+      aBaseVal,
+      msgPrefix + "(2/3 of the way through animation) - " + aReasonStatic,
+    ]);
+    seekList.push([
+      aTimeData.getEndTime(),
+      aBaseVal,
+      msgPrefix + "(at animation end) - " + aReasonStatic,
+    ]);
+    seekList.push([
+      aTimeData.getEndTime() + aTimeData.getDur(),
+      aBaseVal,
+      msgPrefix + "(after animation end) - " + aReasonStatic,
+    ]);
+    return seekList;
+  },
+};
+extend(AnimTestcasePaced, AnimTestcase);
+
+/*
+ * A testcase for an <animateMotion> animation.
+ *
+ * @param aAttrValueHash   A hash-map mapping attribute names to values.
+ *                         Should include at least 'path', 'values', 'to'
+ *                         or 'by' to describe the motion path.
+ * @param aCtmMap  A hash-map that contains summaries of the expected resulting
+ *                 CTM at various points during the animation. The CTM is
+ *                 summarized as a tuple of three numbers: [tX, tY, theta]
+                   (indicating a translate(tX,tY) followed by a rotate(theta))
+ *      - ctm0:   The CTM summary at the start of the animation
+ *      - ctm1_6: The CTM summary at exactly 1/6 through animation
+ *      - ctm1_3: The CTM summary at exactly 1/3 through animation
+ *      - ctm2_3: The CTM summary at exactly 2/3 through animation
+ *      - ctm1:   The CTM summary at the animation endpoint
+ *
+ *  NOTE: For paced-mode animation (the default for animateMotion), the math
+ *  works out easiest if:
+ *    (a) our motion path has 3 points: vA, vB, vC
+ *    (b) dist(vB, vC) = 2 * dist(vA, vB)
+ *  (See discussion in header comment for AnimTestcasePaced.)
+ *
+ * @param aSkipReason  If this test-case is known to currently fail, this
+ *                     parameter should be a string explaining why.
+ *                     Otherwise, this value should be null (or omitted).
+ */
+function AnimMotionTestcase(aAttrValueHash, aCtmMap, aSkipReason) {
+  this.attrValueHash = aAttrValueHash;
+  this.ctmMap = aCtmMap;
+  this.skipReason = aSkipReason;
+  if (
+    this.ctmMap &&
+    (!this.ctmMap.ctm0 ||
+      !this.ctmMap.ctm1_6 ||
+      !this.ctmMap.ctm1_3 ||
+      !this.ctmMap.ctm2_3 ||
+      !this.ctmMap.ctm1)
+  ) {
+    ok(false, "This AnimMotionTestcase has an incomplete CTM map");
+  }
+}
+AnimMotionTestcase.prototype = {
+  // Member variables
+  _animElementTagName: "animateMotion",
+
+  // Implementations of inherited methods that we need to override:
+  // --------------------------------------------------------------
+  setupAnimationElement(aAnimAttr, aTimeData, aIsFreeze) {
+    var animElement = document.createElementNS(
+      SVG_NS,
+      this._animElementTagName
+    );
+    animElement.setAttribute("begin", aTimeData.getBeginTime());
+    animElement.setAttribute("dur", aTimeData.getDur());
+    if (aIsFreeze) {
+      animElement.setAttribute("fill", "freeze");
+    }
+    for (var attrName in this.attrValueHash) {
+      if (attrName == "mpath") {
+        this.createPath(this.attrValueHash[attrName]);
+        this.createMpath(animElement);
+      } else {
+        animElement.setAttribute(attrName, this.attrValueHash[attrName]);
+      }
+    }
+    return animElement;
+  },
+
+  createPath(aPathDescription) {
+    var path = document.createElementNS(SVG_NS, "path");
+    path.setAttribute("d", aPathDescription);
+    path.setAttribute("id", MPATH_TARGET_ID);
+    return SMILUtil.getSVGRoot().appendChild(path);
+  },
+
+  createMpath(aAnimElement) {
+    var mpath = document.createElementNS(SVG_NS, "mpath");
+    mpath.setAttributeNS(XLINK_NS, "href", "#" + MPATH_TARGET_ID);
+    return aAnimElement.appendChild(mpath);
+  },
+
+  // Override inherited seekAndTest method since...
+  // (a) it expects a computedValMap and we have a computed-CTM map instead
+  // and (b) it expects we might have no effect (for non-animatable attrs)
+  buildSeekList(aAnimAttr, aBaseVal, aTimeData, aIsFreeze) {
+    var seekList = new Array();
+    var msgPrefix = "CTM mismatch ";
+    seekList.push([
+      aTimeData.getBeginTime(),
+      CTMUtil.generateCTM(this.ctmMap.ctm0),
+      msgPrefix + "at start of animation",
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(1 / 6),
+      CTMUtil.generateCTM(this.ctmMap.ctm1_6),
+      msgPrefix + "1/6 of the way through animation.",
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(1 / 3),
+      CTMUtil.generateCTM(this.ctmMap.ctm1_3),
+      msgPrefix + "1/3 of the way through animation.",
+    ]);
+    seekList.push([
+      aTimeData.getFractionalTime(2 / 3),
+      CTMUtil.generateCTM(this.ctmMap.ctm2_3),
+      msgPrefix + "2/3 of the way through animation.",
+    ]);
+
+    var finalMsg;
+    var expectedEndVal;
+    if (aIsFreeze) {
+      expectedEndVal = CTMUtil.generateCTM(this.ctmMap.ctm1);
+      finalMsg =
+        aAnimAttr.attrName +
+        ": [freeze-mode] checking that final value is set ";
+    } else {
+      expectedEndVal = aBaseVal;
+      finalMsg =
+        aAnimAttr.attrName +
+        ": [remove-mode] checking that animation is cleared ";
+    }
+    seekList.push([
+      aTimeData.getEndTime(),
+      expectedEndVal,
+      finalMsg + "at end of animation",
+    ]);
+    seekList.push([
+      aTimeData.getEndTime() + aTimeData.getDur(),
+      expectedEndVal,
+      finalMsg + "after end of animation",
+    ]);
+    return seekList;
+  },
+
+  // Override inherited seekAndTest method
+  // (Have to use assertCTMEqual() instead of is() for comparison, to check each
+  // component of the CTM and to allow for a small margin of error.)
+  seekAndTest(aSeekList, aTargetElem, aTargetAttr) {
+    var svg = document.getElementById("svg");
+    for (var i in aSeekList) {
+      var entry = aSeekList[i];
+      SMILUtil.getSVGRoot().setCurrentTime(entry[0]);
+      CTMUtil.assertCTMEqual(
+        aTargetElem.getCTM(),
+        entry[1],
+        CTMUtil.CTM_COMPONENTS_ALL,
+        entry[2],
+        false
+      );
+    }
+  },
+
+  // Override "runTest" method so we can remove any <path> element that we
+  // created at the end of each test.
+  runTest(aTargetElem, aTargetAttr, aTimeData, aIsFreeze) {
+    AnimTestcase.prototype.runTest.apply(this, [
+      aTargetElem,
+      aTargetAttr,
+      aTimeData,
+      aIsFreeze,
+    ]);
+    var pathElem = document.getElementById(MPATH_TARGET_ID);
+    if (pathElem) {
+      SMILUtil.getSVGRoot().removeChild(pathElem);
+    }
+  },
+};
+extend(AnimMotionTestcase, AnimTestcase);
+
+// MAIN METHOD
+function testBundleList(aBundleList, aTimingData) {
+  for (var bundleIdx in aBundleList) {
+    aBundleList[bundleIdx].go(aTimingData);
+  }
+}
diff --git a/dom/smil/test/smilXHR_helper.svg b/dom/smil/test/smilXHR_helper.svg
new file mode 100644
index 0000000000..cb0b51c360
--- /dev/null
+++ b/dom/smil/test/smilXHR_helper.svg
@@ -0,0 +1,8 @@
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px">
+  <circle id="circ" cx="20" cy="20" r="15" fill="blue">
+    <animate id="animXML" attributeName="cx" attributeType="XML"
+             from="500" to="600" begin="0s" dur="4s"/>
+    <animate id="animCSS" attributeName="opacity" attributeType="CSS"
+             from="0.2" to="0.3" begin="0s" dur="4s"/>
+  </circle>
+</svg>
diff --git a/dom/smil/test/test_smilAccessKey.xhtml b/dom/smil/test/test_smilAccessKey.xhtml
new file mode 100644
index 0000000000..5910dc1c27
--- /dev/null
+++ b/dom/smil/test/test_smilAccessKey.xhtml
@@ -0,0 +1,79 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL accessKey support</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank"
+  href="https://bugzilla.mozilla.org/show_bug.cgi?id=587910">Mozilla Bug
+  587910</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px">
+  <circle cx="20" cy="20" r="15" fill="blue" id="circle"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for lack of SMIL accessKey support **/
+
+const gSvgns = 'http://www.w3.org/2000/svg';
+SimpleTest.waitForExplicitFinish();
+
+function main()
+{
+  testBeginValueIsNotSupported('accessKey(a)');
+  testBeginValueIsNotSupported('accesskey(a)');
+
+  is(getStartTime('accesskey(a); 1s'), 1,
+     'Start time for accesskey(a) followed by a literal time');
+  is(getStartTime('3s; accessKey(a)'), 3,
+     'Start time for accesskey(a) preceded by a literal time');
+
+  SimpleTest.finish();
+}
+
+function createAnim(beginSpec) {
+  const anim = document.createElementNS(gSvgns, 'animate');
+  anim.setAttribute('attributeName', 'cx');
+  anim.setAttribute('values', '0; 100');
+  anim.setAttribute('dur', '10s');
+  anim.setAttribute('begin', beginSpec);
+  return document.getElementById('circle').appendChild(anim);
+}
+
+function testBeginValueIsNotSupported(beginSpec) {
+  const anim = createAnim(beginSpec);
+
+  try {
+    anim.getStartTime();
+    ok(false,
+       `Should have failed to get start time for begin value: ${beginSpec}`);
+  } catch(e) {
+    is(e.name, 'InvalidStateError', `Unexpected exception: ${e.name}`);
+    is(e.code, DOMException.INVALID_STATE_ERR,
+       `Unexpected exception code: ${e.code}`);
+  }
+
+  anim.remove();
+}
+
+function getStartTime(beginSpec) {
+  const anim = createAnim(beginSpec);
+  let startTime;
+  try {
+    startTime = anim.getStartTime();
+  } catch (e) { }
+  anim.remove();
+
+  return startTime;
+}
+
+window.addEventListener('load', main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilAdditionFallback.html b/dom/smil/test/test_smilAdditionFallback.html
new file mode 100644
index 0000000000..a73457728c
--- /dev/null
+++ b/dom/smil/test/test_smilAdditionFallback.html
@@ -0,0 +1,30 @@
+<!doctype html>
+<meta charset=utf-8>
+<head>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<p id=display></p>
+<div id=content>
+<svg id=svg>
+<!-- These two animations will have a default duration of indefinite which means
+     they will keep producing their first value forever -->
+<animate calcMode="discrete" attributeName="height" by="10" dur="1s"
+  fill="freeze"/>
+<animate calcMode="discrete" attributeName="height" by="10" dur="1s"
+  fill="freeze"/>
+</svg>
+</div>
+<pre id="test">
+<script>
+'use strict';
+
+SimpleTest.waitForExplicitFinish();
+
+window.addEventListener('load', () => {
+  const svg = document.getElementById('svg');
+  is(getComputedStyle(svg).height, '0px', 'Computed height should be zero');
+  SimpleTest.finish();
+});
+</script>
+</pre>
diff --git a/dom/smil/test/test_smilAnimateMotion.xhtml b/dom/smil/test/test_smilAnimateMotion.xhtml
new file mode 100644
index 0000000000..68ac7fb96a
--- /dev/null
+++ b/dom/smil/test/test_smilAnimateMotion.xhtml
@@ -0,0 +1,51 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=436418
+-->
+<head>
+  <title>Test for animateMotion behavior</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <script type="text/javascript" src="db_smilAnimateMotion.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=436418">Mozilla Bug 436418</a>
+<p id="display"></p>
+<div id="content" style="visibility: hidden">
+
+<!-- NOTE: Setting font-size so we can test 'em' units -->
+<svg xmlns="http://www.w3.org/2000/svg"
+     width="200px" height="200px" style="font-size: 500px"
+     onload="this.pauseAnimations()">
+  <!-- XXXdholbert Right now, 'em' conversions are correct if we set font-size
+       on rect using the inline style attr. However, if we use 'font-size' attr,
+       then 'em' units end up using the inherited font-size instead. Bug? -->
+  <rect x="20" y="20" width="200" height="200" style="font-size: 10px"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+SimpleTest.waitForExplicitFinish();
+
+function main()
+{
+  // Start out with document paused
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var timingData = new SMILTimingData(1.0, 6.0);
+  testBundleList(gMotionBundles, timingData);
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilAnimateMotionInvalidValues.xhtml b/dom/smil/test/test_smilAnimateMotionInvalidValues.xhtml
new file mode 100644
index 0000000000..c2d72e5435
--- /dev/null
+++ b/dom/smil/test/test_smilAnimateMotionInvalidValues.xhtml
@@ -0,0 +1,176 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=436418
+-->
+<head>
+  <title>Test for animateMotion acceptance of invalid values</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js" />
+  <script type="text/javascript" src="smilAnimateMotionValueLists.js" />
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=436418">Mozilla Bug 436418</a>
+<p id="display"></p>
+<div id="content" style="visibility: hidden">
+<svg xmlns="http://www.w3.org/2000/svg" id="svg"
+     width="200px" height="200px"
+     onload="this.pauseAnimations()">
+  <rect id="rect" x="20" y="20" width="200" height="200"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+// Constant strings (& string-arrays)
+const SVGNS = "http://www.w3.org/2000/svg";
+const XLINKNS = "http://www.w3.org/1999/xlink";
+
+// Constant objects
+const gSvg = document.getElementById("svg");
+const gRect = document.getElementById("rect");
+const gUnAnimatedCTM = gRect.getCTM();
+
+SimpleTest.waitForExplicitFinish();
+
+function createAnim()
+{
+  var anim = document.createElementNS(SVGNS, "animateMotion");
+  anim.setAttribute("dur", "2s");
+  return gRect.appendChild(anim);
+}
+
+function removeElem(aElem)
+{
+  aElem.remove();
+}
+
+function testAttr(aAttrName, aAttrValueArray, aIsValid)
+{
+  var componentsToCheck;
+
+  for (var i in aAttrValueArray) {
+    var curVal = aAttrValueArray[i];
+    var anim = createAnim();
+    anim.setAttribute(aAttrName, curVal);
+    if (aAttrName == "rotate") {
+      // Apply a diagonal translation (so rotate='auto' will have an effect)
+      // and just test the rotation matrix components
+      anim.setAttribute("values", "0 0; 50 50");
+      componentsToCheck = CTMUtil.CTM_COMPONENTS_ROTATE;
+    } else {
+      // Apply a supplementary rotation to make sure that we don't apply it if
+      // our value is rejected.
+      anim.setAttribute("rotate", Math.PI/4);
+      componentsToCheck = CTMUtil.CTM_COMPONENTS_ALL;
+      if (aAttrName == "keyPoints") {
+        // Add three times so we can test a greater range of values for
+        // keyPoints
+        anim.setAttribute("values", "0 0; 25 25; 50 50");
+        anim.setAttribute("keyTimes", "0; 0.5; 1");
+        anim.setAttribute("calcMode", "discrete");
+      }
+    }
+
+    var curCTM = gRect.getCTM();
+    if (aIsValid) {
+      var errMsg = "CTM should have changed when applying animateMotion " +
+        "with '" + aAttrName + "' set to valid value '" + curVal + "'";
+      CTMUtil.assertCTMNotEqual(curCTM, gUnAnimatedCTM, componentsToCheck,
+                                errMsg, false);
+    } else {
+      var errMsg = "CTM should not have changed when applying animateMotion " +
+        "with '" + aAttrName + "' set to invalid value '" + curVal + "'";
+      CTMUtil.assertCTMEqual(curCTM, gUnAnimatedCTM, componentsToCheck,
+                             errMsg, false);
+    }
+    removeElem(anim);
+  }
+}
+
+function createPath(aPathDescription)
+{
+  var path = document.createElementNS(SVGNS, "path");
+  path.setAttribute("d", aPathDescription);
+  path.setAttribute("id", "thePath");
+  return gSvg.appendChild(path);
+}
+
+function createMpath(aAnimElement)
+{
+  var mpath = document.createElementNS(SVGNS, "mpath");
+  mpath.setAttributeNS(XLINKNS, "href", "#thePath");
+  return aAnimElement.appendChild(mpath);
+}
+
+function testMpathElem(aPathValueArray, aIsValid)
+{
+  for (var i in aPathValueArray) {
+    var curVal = aPathValueArray[i];
+    var anim = createAnim();
+    var mpath = createMpath(anim);
+    var path = createPath(curVal);
+
+    // Apply a supplementary rotation to make sure that we don't apply it if
+    // our value is rejected.
+    anim.setAttribute("rotate", Math.PI/4);
+    componentsToCheck = CTMUtil.CTM_COMPONENTS_ALL;
+
+    if (aIsValid) {
+      var errMsg = "CTM should have changed when applying animateMotion " +
+        "with mpath linking to a path with valid value '" + curVal + "'";
+
+      CTMUtil.assertCTMNotEqual(gRect.getCTM(), gUnAnimatedCTM,
+                                componentsToCheck, errMsg, false);
+    } else {
+      var errMsg = "CTM should not have changed when applying animateMotion " +
+        "with mpath linking to a path with invalid value '" + curVal + "'";
+      CTMUtil.assertCTMEqual(gRect.getCTM(), gUnAnimatedCTM,
+                             componentsToCheck, errMsg, false);
+    }
+    removeElem(anim);
+    removeElem(path);
+    removeElem(mpath);
+ } 
+}
+
+// Main Function
+function main()
+{
+  // Start out with document paused
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  testAttr("values", gValidValues, true);
+  testAttr("values", gInvalidValues, false);
+
+  testAttr("rotate", gValidRotate, true);
+  testAttr("rotate", gInvalidRotate, false);
+
+  testAttr("to", gValidToBy, true);
+  testAttr("to", gInvalidToBy, false);
+
+  testAttr("by", gValidToBy, true);
+  testAttr("by", gInvalidToBy, false);
+
+  testAttr("path", gValidPath, true);
+  testAttr("path", gInvalidPath, false);
+  testAttr("path", gValidPathWithErrors, true);
+
+  testAttr("keyPoints", gValidKeyPoints, true);
+  testAttr("keyPoints", gInvalidKeyPoints, false);
+
+  testMpathElem(gValidPath, true);
+  testMpathElem(gInvalidPath, false);
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilAnimateMotionOverrideRules.xhtml b/dom/smil/test/test_smilAnimateMotionOverrideRules.xhtml
new file mode 100644
index 0000000000..3a147cd094
--- /dev/null
+++ b/dom/smil/test/test_smilAnimateMotionOverrideRules.xhtml
@@ -0,0 +1,215 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=436418
+-->
+<head>
+  <title>Test for overriding of path-defining attributes for animateMotion</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js" />
+  <script type="text/javascript" src="smilAnimateMotionValueLists.js" />
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=436418">Mozilla Bug 436418</a>
+<p id="display"></p>
+<div id="content" style="visibility: hidden">
+<svg xmlns="http://www.w3.org/2000/svg" id="svg"
+     width="200px" height="200px"
+     onload="this.pauseAnimations()">
+  <!-- Paths for mpath to refer to -->
+  <path id="validPathElem"   d="M10 10 h-10"/>
+  <path id="invalidPathElem" d="abc"/>
+
+  <!-- The rect whose motion is animated -->
+  <rect id="rect" x="20" y="20" width="200" height="200"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+// Constant strings (& string-arrays)
+const SVGNS   = "http://www.w3.org/2000/svg";
+const XLINKNS = "http://www.w3.org/1999/xlink";
+
+// Constant objects
+const gSvg = document.getElementById("svg");
+const gRect = document.getElementById("rect");
+const gUnAnimatedCTM = gRect.getCTM();
+
+// Values for path-defining attributes, and their expected
+// CTMs halfway through the animation
+var gMpathValidTarget    = "#validPathElem";
+var gMpathCTM = CTMUtil.generateCTM([ 5, 10, 0 ]);
+
+var gMpathInvalidTargetA = "#invalidPathElem";
+var gMpathInvalidTargetB = "#nonExistentElem";
+
+var gInvalidAttrValue = "i-am-invalid"; // Invalid for all tested attributes
+
+var gPathValidValue = "M20 20 h10";
+var gPathCTM = CTMUtil.generateCTM([ 25, 20, 0 ]);
+
+var gValuesValidValue = "30 30; 40 30"
+var gValuesCTM = CTMUtil.generateCTM([ 35, 30, 0 ]);
+
+var gFromValidValue = "50 50";
+
+var gByValidValue =   "10 2";
+var gPureByCTM = CTMUtil.generateCTM([  5,  1, 0 ]);
+var gFromByCTM = CTMUtil.generateCTM([ 55, 51, 0 ]);
+
+var gToValidValue =   "80 60";
+var gPureToCTM = CTMUtil.generateCTM([ 40, 30, 0 ]);
+var gFromToCTM = CTMUtil.generateCTM([ 65, 55, 0 ]);
+
+
+SimpleTest.waitForExplicitFinish();
+
+function createAnim()
+{
+  var anim = document.createElementNS(SVGNS, "animateMotion");
+  return gRect.appendChild(anim);
+}
+
+function removeElem(aElem)
+{
+  aElem.remove();
+}
+
+function createMpath(aAnimElement, aHrefVal)
+{
+  var mpath = document.createElementNS(SVGNS, "mpath");
+  mpath.setAttributeNS(XLINKNS, "href", aHrefVal);
+  return aAnimElement.appendChild(mpath);
+}
+
+function runTest() {
+  // Start out with valid values for all path-defining attributes
+  var attrSettings = {
+    "mpath"  : gMpathValidTarget,
+    "path"   : gPathValidValue,
+    "values" : gValuesValidValue,
+    "from"   : gFromValidValue,
+    "to"     : gToValidValue,
+    "by"     : gByValidValue,
+  };
+
+  // Test that <mpath> overrides everything below it
+  testAttrSettings(attrSettings, gMpathCTM,
+                   "<mpath> should win");
+  var mpathInvalidTargets = [gMpathInvalidTargetA, gMpathInvalidTargetB];
+  for (var i in mpathInvalidTargets) {
+    var curInvalidValue = mpathInvalidTargets[i];
+    attrSettings.mpath = curInvalidValue;
+    testAttrSettings(attrSettings, gUnAnimatedCTM,
+                     "invalid <mpath> should block animation");
+  }
+  delete attrSettings.mpath;
+
+  // Test that 'path' overrides everything below it
+  testAttrSettings(attrSettings, gPathCTM,
+                   "'path' should win vs all but mpath");
+  attrSettings.path = gInvalidAttrValue;
+  testAttrSettings(attrSettings, gUnAnimatedCTM,
+                   "invalid 'path' should block animation vs all but mpath");
+  delete attrSettings.path;
+
+  // Test that 'values' overrides everything below it
+  testAttrSettings(attrSettings, gValuesCTM,
+                   "'values' should win vs from/by/to");
+  attrSettings.values = gInvalidAttrValue;
+  testAttrSettings(attrSettings, gUnAnimatedCTM,
+                   "invalid 'values' should block animation vs from/by/to");
+  delete attrSettings.values;
+
+  // Test that 'from' & 'to' overrides 'by'
+  testAttrSettings(attrSettings, gFromToCTM,
+                   "'from/to' should win vs 'by'");
+  attrSettings.to = gInvalidAttrValue;
+  testAttrSettings(attrSettings, gUnAnimatedCTM,
+                   "invalid 'to' should block animation vs 'by'");
+  delete attrSettings.to;
+
+  // Test that 'from' & 'by' are effective
+  testAttrSettings(attrSettings, gFromByCTM,
+                   "'from/by' should be visible");
+  attrSettings.by = gInvalidAttrValue;
+  testAttrSettings(attrSettings, gUnAnimatedCTM,
+                   "invalid 'by' should block animation");
+  delete attrSettings.from;
+
+  // REINSERT "to" & fix up "by" so we can test pure-"to" vs pure-"by"
+  attrSettings.to = gToValidValue;
+  attrSettings.by = gByValidValue;
+  testAttrSettings(attrSettings, gPureToCTM,
+                   "pure-'to' should be effective & beat pure-'by'");
+  attrSettings.to = gInvalidAttrValue;
+  testAttrSettings(attrSettings, gUnAnimatedCTM,
+                   "invalid pure-'to' should block animation vs pure-'by'");
+  delete attrSettings.to;
+
+  // Test that pure-"by" is effective
+  testAttrSettings(attrSettings, gPureByCTM,
+                   "pure-by should be visible");
+  attrSettings.by = gInvalidAttrValue;
+  testAttrSettings(attrSettings, gUnAnimatedCTM,
+                   "invalid 'by' should block animation");
+  delete attrSettings.by;
+
+  // Make sure that our hash is empty now.
+  for (var unexpectedKey in attrSettings) {
+    ok(false, "Unexpected mapping remains in attrSettings: " +
+       unexpectedKey + "-->" + unexpectedValue);
+  }
+}
+
+function testAttrSettings(aAttrValueHash, aExpectedCTM, aErrMsg)
+{
+  var isDebug = false; // XXdholbert
+  !isDebug || todo(false, "ENTERING testAttrSettings");
+  // Set up animateMotion element
+  var animElement = document.createElementNS(SVGNS, "animateMotion");
+  animElement.setAttribute("dur", "2s");
+  for (var attrName in aAttrValueHash) {
+    !isDebug || todo(false, "setting '" + attrName +"' to '" +
+                     aAttrValueHash[attrName] +"'");
+    if (attrName == "mpath") {
+      createMpath(animElement, aAttrValueHash[attrName]);
+    } else {
+      animElement.setAttribute(attrName, aAttrValueHash[attrName]);
+    }
+  }
+
+  gRect.appendChild(animElement);
+
+  // Seek to halfway through animation
+  SMILUtil.getSVGRoot().setCurrentTime(1); // Seek halfway through animation
+
+  // Check CTM against expected value
+  CTMUtil.assertCTMEqual(gRect.getCTM(), aExpectedCTM,
+                         CTMUtil.CTM_COMPONENTS_ALL, aErrMsg, false);
+
+  // CLEAN UP
+  SMILUtil.getSVGRoot().setCurrentTime(0);
+  removeElem(animElement);
+}
+
+// Main Function
+function main()
+{
+  // Start out with document paused
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  runTest();
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilBackwardsSeeking.xhtml b/dom/smil/test/test_smilBackwardsSeeking.xhtml
new file mode 100644
index 0000000000..20974e6de3
--- /dev/null
+++ b/dom/smil/test/test_smilBackwardsSeeking.xhtml
@@ -0,0 +1,191 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for backwards seeking behavior </title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" />
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for backwards seeking behavior  **/
+
+var gSvg = document.getElementById("svg");
+
+SimpleTest.waitForExplicitFinish();
+
+function main()
+{
+  // Pause our document, so that the setCurrentTime calls are the only
+  // thing affecting document time
+  gSvg.pauseAnimations();
+
+  // We define a series of scenarios, sample times, and expected return values
+  // from getStartTime.
+  //
+  // Each scenario is basically a variation on the following arrangement:
+  //
+  // <svg>
+  //   <set ... dur="1s" begin="<A-BEGIN>"/>
+  //   <set ... dur="1s" begin="<B-BEGIN>"/>
+  // </svg>
+  //
+  // Each test then consists of the following:
+  //    animA: attributes to be applied to a
+  //    animB: attributes to be applied to b
+  //    times: a series of triples which consist of:
+  //             <sample time, a's expected start time, b's expected start time>
+  //           * The sample time is the time passed to setCurrentTime and so is
+  //             in seconds.
+  //           * The expected start times are compared with the return value of
+  //             getStartTime. To check for an unresolved start time where
+  //             getStartTime would normally throw an exception use
+  //             'unresolved'.
+  //           * We also allow the special notation to indicate a call to
+  //             beginElement
+  //             <'beginElementAt', id of animation element, offset>
+  //
+  // In the diagrams below '^' means the time before the seek and '*' is the
+  // seek time.
+  var testCases = Array();
+
+  // 0: Simple case
+  //
+  //   A:     +-------
+  //   B:     +-------       begin: a.begin
+  //        *            ^
+  testCases[0] = {
+    'animA': {'begin':'1s', 'id':'a'},
+    'animB': {'begin':'a.begin'},
+    'times': [ [0, 1, 1],
+               [1, 1, 1],
+               [2, 'unresolved', 'unresolved'],
+               [0, 1, 1],
+               [1.5, 1, 1],
+               [1, 1, 1],
+               [2, 'unresolved', 'unresolved'] ]
+  };
+
+  // 1: Restored times should be live
+  //
+  // When we restore times they should be live. So we have the following
+  // scenario.
+  //
+  //   A:     +-------
+  //   B:     +-------       begin: a.begin
+  //       *            ^
+  //
+  // Then we call beginElement at an earlier time which should give us the
+  // following.
+  //
+  //   A:   +-------
+  //   B:   +-------
+  //       *            ^
+  //
+  //  If the times are not live however we'll end up with this
+  //
+  //   A:   +-------
+  //   B:   +-+-------
+  //       *            ^
+  testCases[1] = {
+    'animA': {'begin':'1s', 'id':'a', 'restart':'whenNotActive'},
+    'animB': {'begin':'a.begin', 'restart':'always'},
+    'times': [ [0, 1, 1],
+               [2, 'unresolved', 'unresolved'],
+               [0.25, 1, 1],
+               ['beginElementAt', 'a', 0.25], // = start time of 0.5
+               [0.25, 0.5, 0.5],
+               [1, 0.5, 0.5],
+               [1.5, 'unresolved', 'unresolved'] ]
+  };
+
+  // 2: Multiple intervals A
+  //
+  //   A:  +-  +-
+  //   B:          +-  +-   begin: a.begin+4s
+  //             *    ^
+  testCases[2] = {
+    'animA': {'begin':'1s; 3s', 'id':'a'},
+    'animB': {'begin':'a.begin+4s'},
+    'times': [ [0, 1, 5],
+               [3, 3, 5],
+               [6.5, 'unresolved', 7],
+               [4, 'unresolved', 5],
+               [6, 'unresolved', 7],
+               [2, 3, 5],
+               ['beginElementAt', 'a', 0],
+               [2, 2, 5],
+               [5, 'unresolved', 5],
+               [6, 'unresolved', 6],
+               [7, 'unresolved', 7],
+               [8, 'unresolved', 'unresolved'] ]
+  };
+
+  for (var i = 0; i < testCases.length; i++) {
+    gSvg.setCurrentTime(0);
+    var test = testCases[i];
+
+    // Create animation elements
+    var animA = createAnim(test.animA);
+    var animB = createAnim(test.animB);
+
+    // Run samples
+    for (var j = 0; j < test.times.length; j++) {
+      var times = test.times[j];
+      if (times[0] == 'beginElementAt') {
+        var anim = getElement(times[1]);
+        anim.beginElementAt(times[2]);
+      } else {
+        gSvg.setCurrentTime(times[0]);
+        checkStartTime(animA, times[1], times[0], i, 'a');
+        checkStartTime(animB, times[2], times[0], i, 'b');
+      }
+    }
+
+    // Tidy up
+    animA.remove();
+    animB.remove();
+  }
+
+  SimpleTest.finish();
+}
+
+function createAnim(attr)
+{
+  const svgns = "http://www.w3.org/2000/svg";
+  var anim = document.createElementNS(svgns, 'set');
+  anim.setAttribute('attributeName','x');
+  anim.setAttribute('to','10');
+  anim.setAttribute('dur','1s');
+  for (name in attr) {
+    anim.setAttribute(name, attr[name]);
+  }
+  return gSvg.appendChild(anim);
+}
+
+function checkStartTime(anim, expectedStartTime, sampleTime, caseNum, id)
+{
+  var startTime = 'unresolved';
+  try {
+    startTime = anim.getStartTime();
+  } catch (e) {
+    if (e.name != "InvalidStateError" ||
+        e.code != DOMException.INVALID_STATE_ERR)
+      throw e;
+  }
+
+  var msg = "Test case " + caseNum + ", t=" + sampleTime + " animation '" +
+    id + "': Unexpected getStartTime:";
+  is(startTime, expectedStartTime, msg);
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilCSSFontStretchRelative.xhtml b/dom/smil/test/test_smilCSSFontStretchRelative.xhtml
new file mode 100644
index 0000000000..01988a881b
--- /dev/null
+++ b/dom/smil/test/test_smilCSSFontStretchRelative.xhtml
@@ -0,0 +1,102 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for Animation Behavior on CSS Properties</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg">
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/* This testcase verifies that animated values of "wider" and "narrower" for
+   "font-stretch" have the expected effect, across all possible inherited
+   values of the property.
+   XXXdholbert Currently, we don't support animating relative values of
+   font-stretch, so most of the tests here use todo_is() rather than is().
+*/
+
+SimpleTest.waitForExplicitFinish();
+
+const gPropertyName="font-stretch";
+
+// List of non-relative font-stretch values, from smallest to largest
+const gFontStretchValues = [
+  ["ultra-condensed", "50%"],
+  ["extra-condensed", "62.5%"],
+  ["condensed", "75%"],
+  ["semi-condensed", "87.5%"],
+  ["normal", "100%"],
+  ["semi-expanded", "112.5%"],
+  ["expanded", "125%"],
+  ["extra-expanded", "150%"],
+  ["ultra-expanded", "200%"],
+];
+
+function testFontStretchValue([baseValue, computedValue], [narrowerStep, computedNarrowerStep], [widerStep, computedWiderStep])
+{
+  var svg = SMILUtil.getSVGRoot();
+  var gElem = document.createElementNS(SVG_NS, "g");
+  gElem.setAttribute("style", "font-stretch: " + baseValue);
+  svg.appendChild(gElem);
+
+  var textElem = document.createElementNS(SVG_NS, "text");
+  gElem.appendChild(textElem);
+
+  var animElem = document.createElementNS(SVG_NS, "set");
+  animElem.setAttribute("attributeName", gPropertyName);
+  animElem.setAttribute("attributeType", "CSS");
+  animElem.setAttribute("begin", "0s");
+  animElem.setAttribute("dur", "indefinite");
+  textElem.appendChild(animElem);
+
+  // CHECK EFFECT OF 'narrower'
+  // NOTE: Using is() instead of todo_is() for ultra-condensed, since
+  // 'narrower' has no effect on that value.
+  var myIs = (baseValue == "ultra-condensed" ? is : todo_is);
+  animElem.setAttribute("to", "narrower");
+  SMILUtil.getSVGRoot().setCurrentTime(1.0); // Force a resample
+  myIs(SMILUtil.getComputedStyleSimple(textElem, gPropertyName), computedNarrowerStep,
+       "checking effect of 'narrower' on inherited value '" + baseValue + "'");
+
+  // CHECK EFFECT OF 'wider'
+  // NOTE: using is() instead of todo_is() for ultra-expanded, since
+  // 'wider' has no effect on that value.
+  myIs = (baseValue == "ultra-expanded" ? is : todo_is);
+  animElem.setAttribute("to", "wider");
+  SMILUtil.getSVGRoot().setCurrentTime(1.0); // Force a resample
+  myIs(SMILUtil.getComputedStyleSimple(textElem, gPropertyName), computedWiderStep,
+          "checking effect of 'wider' on inherited value '" + baseValue + "'");
+
+  // Removing animation should clear animated effects
+  textElem.removeChild(animElem);
+  svg.removeChild(gElem);
+}
+
+function main()
+{
+  var valuesList = gFontStretchValues;
+  for (var baseIdx in valuesList) {
+    // 'narrower' and 'wider' are expected to shift us by one slot, but not
+    // past the ends of the list of possible values.
+    var narrowerIdx = Math.max(baseIdx - 1, 0);
+    var widerIdx =    Math.min(baseIdx + 1, valuesList.length - 1);
+
+    testFontStretchValue(valuesList[baseIdx],
+                         valuesList[narrowerIdx], valuesList[widerIdx]);
+  }
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilCSSFromBy.xhtml b/dom/smil/test/test_smilCSSFromBy.xhtml
new file mode 100644
index 0000000000..586305fb8a
--- /dev/null
+++ b/dom/smil/test/test_smilCSSFromBy.xhtml
@@ -0,0 +1,49 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for Animation Behavior on CSS Properties</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <script type="text/javascript" src="db_smilCSSPropertyList.js"></script>
+  <script type="text/javascript" src="db_smilCSSFromBy.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg xmlns="http://www.w3.org/2000/svg"
+     width="200px" height="200px" font-size="50px" style="color: rgb(50,50,50)"
+     onload="this.pauseAnimations()">
+  <rect x="20" y="20" width="200" height="200"/>
+  <!-- NOTE: hard-wiring 'line-height' so that computed value of 'font' is
+       more predictable. (otherwise, line-height varies depending on platform)
+    -->
+  <text x="20" y="20" style="line-height: 10px !important">testing 123</text>
+  <line/>
+  <marker/>
+  <filter><feDiffuseLighting/></filter>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+SimpleTest.waitForExplicitFinish();
+
+function main()
+{
+  // Start out with document paused
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  testBundleList(gFromByBundles, new SMILTimingData(1.0, 1.0));
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilCSSFromTo.xhtml b/dom/smil/test/test_smilCSSFromTo.xhtml
new file mode 100644
index 0000000000..501adbc4a8
--- /dev/null
+++ b/dom/smil/test/test_smilCSSFromTo.xhtml
@@ -0,0 +1,76 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for Animation Behavior on CSS Properties</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <script type="text/javascript" src="db_smilCSSPropertyList.js"></script>
+  <script type="text/javascript" src="db_smilCSSFromTo.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg xmlns="http://www.w3.org/2000/svg"
+     width="200px" height="200px" font-size="50px" style="color: rgb(50,50,50)"
+     onload="this.pauseAnimations()">
+  <rect x="20" y="20" width="200" height="200"/>
+  <!-- NOTE: hard-wiring 'line-height' so that computed value of 'font' is
+       more predictable. (otherwise, line-height varies depending on platform)
+    -->
+  <text x="20" y="20" style="line-height: 10px !important">testing 123</text>
+  <line/>
+  <image/>
+  <marker/>
+  <clipPath><circle/></clipPath>
+  <filter><feFlood/></filter>
+  <filter><feDiffuseLighting/></filter>
+  <linearGradient><stop/></linearGradient>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+SimpleTest.waitForExplicitFinish();
+
+function checkForUntestedProperties(bundleList)
+{
+  // Create the set of all the properties we know about
+  var propertySet = {};
+  for (propertyLabel in gPropList) {
+    // insert property
+    propertySet[gPropList[propertyLabel].attrName] = null;
+  }
+  // Remove tested properties from the set
+  for (var bundleIdx in bundleList) {
+    var bundle = bundleList[bundleIdx];
+    delete propertySet[bundle.animatedAttribute.attrName];
+  }
+  // Warn about remaining (untested) properties
+  for (var untestedProp in propertySet) {
+    ok(false, "No tests for property '" + untestedProp + "'");
+  }
+}
+
+function main()
+{
+  // Start out with document paused
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  // FIRST: Warn about any properties that are missing tests
+  checkForUntestedProperties(gFromToBundles);
+
+  // Run the actual tests
+  testBundleList(gFromToBundles, new SMILTimingData(1.0, 1.0));
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilCSSInherit.xhtml b/dom/smil/test/test_smilCSSInherit.xhtml
new file mode 100644
index 0000000000..4e262d3aa9
--- /dev/null
+++ b/dom/smil/test/test_smilCSSInherit.xhtml
@@ -0,0 +1,85 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for Animation Behavior on CSS Properties</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="300px" height="200px"
+     onload="this.pauseAnimations()">
+  <!--  At 50% through the animation, the following should be true:
+   * First <g> has font-size = 5px (1/2 between 0px and 10px)
+   * Next <g> has font-size = 10px (1/2 between inherit=5px and 15px)
+   * Next <g> has font-size = 15px (1/2 between inherit=10px and 20px)
+   * Next <g> has font-size = 20px (1/2 between inherit=15px and 25px)
+   * Next <g> has font-size = 25px (1/2 between inherit=20px and 30px)
+   * Next <g> has font-size = 30px (1/2 between inherit=25px and 35px)
+   * Next <g> has font-size = 35px (1/2 between inherit=30px and 40px)
+   * Next <g> has font-size = 40px (1/2 between inherit=35px and 45px)
+   * Next <g> has font-size = 45px (1/2 between inherit=40px and 50px)
+   * Next <g> has font-size = 50px (1/2 between inherit=45px and 55px)
+   * <text> has font-size = 75px (1/2 between inherit=50px and 100px)
+  -->
+  <g><animate attributeName="font-size" attributeType="CSS"
+              from="0px"     to="10px" begin="0s" dur="1s"/>
+  <g><animate attributeName="font-size" attributeType="CSS"
+              from="inherit" to="15px" begin="0s" dur="1s"/>
+  <g><animate attributeName="font-size" attributeType="CSS"
+              from="inherit" to="20px" begin="0s" dur="1s"/>
+  <g><animate attributeName="font-size" attributeType="CSS"
+              from="inherit" to="25px" begin="0s" dur="1s"/>
+  <g><animate attributeName="font-size" attributeType="CSS"
+              from="inherit" to="30px" begin="0s" dur="1s"/>
+  <g><animate attributeName="font-size" attributeType="CSS"
+              from="inherit" to="35px" begin="0s" dur="1s"/>
+  <g><animate attributeName="font-size" attributeType="CSS"
+              from="inherit" to="40px" begin="0s" dur="1s"/>
+  <g><animate attributeName="font-size" attributeType="CSS"
+              from="inherit" to="45px" begin="0s" dur="1s"/>
+  <g><animate attributeName="font-size" attributeType="CSS"
+              from="inherit" to="50px" begin="0s" dur="1s"/>
+  <g><animate attributeName="font-size" attributeType="CSS"
+              from="inherit" to="55px" begin="0s" dur="1s"/>
+  <text y="100px" x="0px">
+    abc
+    <animate attributeName="font-size" attributeType="CSS"
+             from="inherit" to="100px" begin="0s" dur="1s"/>
+  </text></g></g></g></g></g></g></g></g></g></g>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  // Pause & seek to halfway through animation
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+  svg.setCurrentTime(0.5);
+
+  var text = document.getElementsByTagName("text")[0];
+  var computedVal = SMILUtil.getComputedStyleSimple(text, "font-size");
+  var expectedVal = "75px";
+
+  // NOTE: There's a very small chance (1/11! = 1/39,916,800) that we'll happen
+  // to composite our 11 animations in the correct order, in which cast this
+  // "todo_is" test would sporadically pass. I think this is infrequent enough
+  // to accept as a sporadic pass rate until this bug is fixed (at which point
+  // this "todo_is" will become an "is")
+  todo_is(computedVal, expectedVal,
+         "deeply-inherited font-size halfway through animation");
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilCSSInvalidValues.xhtml b/dom/smil/test/test_smilCSSInvalidValues.xhtml
new file mode 100644
index 0000000000..5e8e682af9
--- /dev/null
+++ b/dom/smil/test/test_smilCSSInvalidValues.xhtml
@@ -0,0 +1,59 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for Animation Behavior on CSS Properties</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <script type="text/javascript" src="db_smilCSSPropertyList.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg xmlns="http://www.w3.org/2000/svg"
+     onload="this.pauseAnimations()">
+  <rect x="20" y="20" width="200" height="200"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+SimpleTest.waitForExplicitFinish();
+
+var invalidTestcaseBundles = [
+  new TestcaseBundle(gPropList.opacity, [
+    new AnimTestcaseFromTo("", "",     { noEffect: true }),
+    new AnimTestcaseFromTo("", "0.5",  { noEffect: true }),
+    new AnimTestcaseFromTo(".", "0.5", { noEffect: true }),
+    new AnimTestcaseFromTo("0.5", "-", { noEffect: true }),
+    new AnimTestcaseFromTo("0.5", "bogus",   { noEffect: true }),
+    new AnimTestcaseFromTo("bogus", "bogus", { noEffect: true }),
+  ]),
+  new TestcaseBundle(gPropList.color, [
+    new AnimTestcaseFromTo("", "",            { noEffect: true }),
+    new AnimTestcaseFromTo("", "red",         { noEffect: true }),
+    new AnimTestcaseFromTo("greeeen", "red",  { noEffect: true }),
+    new AnimTestcaseFromTo("rgb(red, 255, 255)", "red", { noEffect: true }),
+    new AnimTestcaseFromTo("#FFFFFFF", "red", { noEffect: true }),
+    new AnimTestcaseFromTo("bogus", "bogus",  { noEffect: true }),
+  ]),
+];
+function main()
+{
+  // Start out with document paused
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  // Run the tests
+  testBundleList(invalidTestcaseBundles, new SMILTimingData(1.0, 1.0));
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilCSSPaced.xhtml b/dom/smil/test/test_smilCSSPaced.xhtml
new file mode 100644
index 0000000000..1f6b3509ae
--- /dev/null
+++ b/dom/smil/test/test_smilCSSPaced.xhtml
@@ -0,0 +1,44 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for Animation Behavior on CSS Properties</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <script type="text/javascript" src="db_smilCSSPropertyList.js"></script>
+  <script type="text/javascript" src="db_smilCSSPaced.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg xmlns="http://www.w3.org/2000/svg"
+     width="200px" height="200px" font-size="50px" style="color: rgb(50,50,50)"
+     onload="this.pauseAnimations()">
+  <rect x="20" y="20" width="200" height="200"/>
+  <text x="20" y="20">testing 123</text>
+  <marker/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+SimpleTest.waitForExplicitFinish();
+
+function main()
+{
+  // Start out with document paused
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  testBundleList(gPacedBundles, new SMILTimingData(1.0, 6.0));
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilChangeAfterFrozen.xhtml b/dom/smil/test/test_smilChangeAfterFrozen.xhtml
new file mode 100644
index 0000000000..97fe131678
--- /dev/null
+++ b/dom/smil/test/test_smilChangeAfterFrozen.xhtml
@@ -0,0 +1,571 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL when things change after an animation is frozen</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=533291">Mozilla Bug 533291</a>
+<p id="display"></p>
+<!-- Bug 628848: The following should be display: none but we currently don't
+     handle percentage lengths properly when the whole fragment is display: none
+     -->
+<div id="content" style="visibility: hidden">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <g id="circleParent">
+    <circle cx="0" cy="20" r="15" fill="blue" id="circle"/>
+  </g>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL values that are context-sensitive **/
+
+/* See bugs 533291 and 562815.
+   
+   The format of each test is basically:
+   1) create some animated and frozen state
+   2) test the animated values
+   3) change the context
+   4) test that context-sensitive animation values have changed
+
+   Ideally, after changing the context (3), the animated state would instantly
+   update. However, this is not currently the case for many situations.
+
+     For CSS properties we have bug 545282 - In animations involving 'inherit'
+     / 'currentColor', changes to inherited value / 'color' don't show up in
+     animated value immediately
+
+     For SVG lengths we have bug 508206 - Relative units used in
+     animation don't update immediately
+
+     (There are a few of todo_is's in the following tests so that if those bugs
+     are ever resolved we'll know to update this test case accordingly.)
+
+   So in between (3) and (4) we force a sample. This is currently done by
+   calling SVGSVGElement.setCurrentTime with the same current time which has the
+   side effect of forcing a sample.
+
+   What we *are* testing is that we're not too zealous with caching animation
+   values whilst in the frozen state. Normally we'd say, "Hey, we're frozen,
+   let's just use the same animation result as last time" but for some
+   context-sensitive animation values that doesn't work.
+*/
+
+/* Global Variables */
+const SVGNS = "http://www.w3.org/2000/svg";
+
+// Animation parameters -- not used for <set> animation
+const ANIM_DUR = "4s";
+const TIME_ANIM_END = "4";
+const TIME_AFTER_ANIM_END = "5";
+
+const gSvg = document.getElementById("svg");
+const gCircle = document.getElementById("circle");
+const gCircleParent = document.getElementById("circleParent");
+
+SimpleTest.waitForExplicitFinish();
+
+// MAIN FUNCTION
+// -------------
+
+function main()
+{
+  ok(gSvg.animationsPaused(), "should be paused by <svg> load handler");
+  is(gSvg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  const tests =
+    [ testBaseValueChange,
+      testCurrentColorChange,
+      testCurrentColorChangeUsingStyle,
+      testCurrentColorChangeOnFallback,
+      testInheritChange,
+      testInheritChangeUsingStyle,
+      testEmUnitChangeOnProp,
+      testEmUnitChangeOnPropBase,
+      testEmUnitChangeOnLength,
+      testPercentUnitChangeOnProp,
+      testPercentUnitChangeOnLength,
+      testRelativeFontSize,
+      testRelativeFontWeight,
+      testRelativeFont,
+      testCalcFontSize,
+      testDashArray,
+      testClip
+     ];
+
+  while (tests.length) {
+    tests.shift()();
+  }
+  SimpleTest.finish();
+}
+
+// HELPER FUNCTIONS
+// ----------------
+function createAnimSetTo(attrName, toVal)
+{
+  var anim = document.createElementNS(SVGNS,"set");
+  anim.setAttribute("attributeName", attrName);
+  anim.setAttribute("to", toVal);
+  return gCircle.appendChild(anim);
+}
+
+function createAnimBy(attrName, byVal)
+{
+  var anim = document.createElementNS(SVGNS,"animate");
+  anim.setAttribute("attributeName", attrName);
+  anim.setAttribute("dur", ANIM_DUR);
+  anim.setAttribute("begin","0s");
+  anim.setAttribute("by", byVal);
+  anim.setAttribute("fill", "freeze");
+  return gCircle.appendChild(anim);
+}
+
+function createAnimFromTo(attrName, fromVal, toVal)
+{
+  var anim = document.createElementNS(SVGNS,"animate");
+  anim.setAttribute("attributeName", attrName);
+  anim.setAttribute("dur", ANIM_DUR);
+  anim.setAttribute("begin","0s");
+  anim.setAttribute("from", fromVal);
+  anim.setAttribute("to", toVal);
+  anim.setAttribute("fill", "freeze");
+  return gCircle.appendChild(anim);
+}
+
+// Common setup code for each test function: seek to 0, and make sure
+// the previous test cleaned up its animations.
+function setupTest() {
+  gSvg.setCurrentTime(0);
+  if (gCircle.firstChild) {
+    ok(false, "Previous test didn't clean up after itself.");
+  }
+}
+
+// THE TESTS
+// ---------
+
+function testBaseValueChange()
+{
+  setupTest();
+  var anim = createAnimBy("cx", "50");
+  gSvg.setCurrentTime(TIME_ANIM_END);
+  is(gCircle.cx.animVal.value, 50,
+     "Checking animated cx as anim ends");
+
+  gSvg.setCurrentTime(TIME_AFTER_ANIM_END);
+  is(gCircle.cx.animVal.value, 50,
+     "Checking animated cx after anim ends");
+
+  gCircle.setAttribute("cx", 20);
+  is(gCircle.cx.animVal.value, 70,
+     "Checking animated cx after anim ends & after changing base val");
+
+  anim.remove(); // clean up
+}
+
+function testCurrentColorChange()
+{
+  gCircle.setAttribute("color", "red"); // At first: currentColor=red
+  var anim = createAnimSetTo("fill", "currentColor");
+
+  gSvg.setCurrentTime(0); // trigger synchronous sample
+  is(SMILUtil.getComputedStyleSimple(gCircle, "fill"), "rgb(255, 0, 0)",
+     "Checking animated fill=currentColor after animating");
+
+  gCircle.setAttribute("color", "lime"); // Change: currentColor=lime
+  // Bug 545282: We should really detect this change and update immediately but
+  // currently we don't until we get sampled again
+  todo_is(SMILUtil.getComputedStyleSimple(gCircle, "fill"), "rgb(0, 255, 0)",
+     "Checking animated fill=currentColor after updating context but before " +
+     "sampling");
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "fill"), "rgb(0, 255, 0)",
+     "Checking animated fill=currentColor after updating context");
+
+  // Clean up
+  gCircle.removeAttribute("color");
+  gCircle.firstChild.remove();
+}
+
+function testCurrentColorChangeUsingStyle()
+{
+  setupTest();
+  gCircle.setAttribute("style", "color: red"); // At first: currentColor=red
+  var anim = createAnimSetTo("fill", "currentColor");
+
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "fill"), "rgb(255, 0, 0)",
+     "Checking animated fill=currentColor after animating (using style attr)");
+
+  gCircle.setAttribute("style", "color: lime"); // Change: currentColor=lime
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "fill"), "rgb(0, 255, 0)",
+     "Checking animated fill=currentColor after updating context "
+     + "(using style attr)");
+
+  // Clean up
+  gCircle.removeAttribute("style");
+  gCircle.firstChild.remove();
+}
+
+function getFallbackColor(pServerStr)
+{
+  return pServerStr.substr(pServerStr.indexOf(" ")+1);
+}
+
+function testCurrentColorChangeOnFallback()
+{
+  setupTest();
+  gCircle.setAttribute("color", "red"); // At first: currentColor=red
+  var anim = createAnimSetTo("fill", "url(#missingGrad) currentColor");
+
+  gSvg.setCurrentTime(0);
+  var fallback =
+    getFallbackColor(SMILUtil.getComputedStyleSimple(gCircle, "fill"));
+  is(fallback, "rgb(255, 0, 0)",
+     "Checking animated fallback fill=currentColor after animating");
+
+  gCircle.setAttribute("color", "lime"); // Change: currentColor=lime
+  gSvg.setCurrentTime(0);
+  fallback = getFallbackColor(SMILUtil.getComputedStyleSimple(gCircle, "fill"));
+  is(fallback, "rgb(0, 255, 0)",
+     "Checking animated fallback fill=currentColor after updating context");
+
+  gCircle.removeAttribute("style");
+  gCircle.firstChild.remove();
+}
+
+function testInheritChange()
+{
+  setupTest();
+  gCircleParent.setAttribute("fill", "red"); // At first: inherit=red
+  var anim = createAnimSetTo("fill", "inherit");
+
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "fill"), "rgb(255, 0, 0)",
+     "Checking animated fill=inherit after animating");
+
+  gCircleParent.setAttribute("fill", "lime"); // Change: inherit=lime
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "fill"), "rgb(0, 255, 0)",
+     "Checking animated fill=inherit after updating context");
+
+  gCircleParent.removeAttribute("fill");
+  gCircle.firstChild.remove();
+}
+
+function testInheritChangeUsingStyle()
+{
+  setupTest();
+  gCircleParent.setAttribute("style", "fill: red"); // At first: inherit=red
+  var anim = createAnimSetTo("fill", "inherit");
+
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "fill"), "rgb(255, 0, 0)",
+     "Checking animated fill=inherit after animating (using style attr)");
+
+  gCircleParent.setAttribute("style", "fill: lime"); // Change: inherit=lime
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "fill"), "rgb(0, 255, 0)",
+     "Checking animated fill=inherit after updating context "
+     + "(using style attr)");
+
+  gCircleParent.removeAttribute("style");
+  gCircle.firstChild.remove();
+}
+
+function testEmUnitChangeOnProp()
+{
+  setupTest();
+  gCircleParent.setAttribute("font-size", "10px"); // At first: font-size: 10px
+  var anim = createAnimSetTo("font-size", "2em");
+
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "font-size"), "20px",
+     "Checking animated font-size=2em after animating ends");
+
+  gCircleParent.setAttribute("font-size", "20px"); // Change: font-size: 20px
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "font-size"), "40px",
+     "Checking animated font-size=2em after updating context");
+
+  gCircleParent.removeAttribute("font-size");
+  gCircle.firstChild.remove();
+}
+
+function testEmUnitChangeOnPropBase()
+{
+  // Test the case where the base value for our animation sandwich is
+  // context-sensitive.
+  // Currently, this is taken care of by the compositor which keeps a cached
+  // base value and compares it with the current base value. This test then just
+  // serves as a regression test in case the compositor's behaviour changes.
+  setupTest();
+  gSvg.setAttribute("font-size", "10px"); // At first: font-size: 10px
+  gCircleParent.setAttribute("font-size", "1em"); // Base: 10px
+  var anim = createAnimBy("font-size", "10px");
+
+  gSvg.setCurrentTime(TIME_AFTER_ANIM_END);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "font-size"), "20px",
+     "Checking animated font-size=20px after anim ends");
+
+  gSvg.setAttribute("font-size", "20px"); // Change: font-size: 20px
+  gSvg.setCurrentTime(TIME_AFTER_ANIM_END);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "font-size"), "30px",
+     "Checking animated font-size=30px after updating context");
+
+  gCircleParent.removeAttribute("font-size");
+  gCircle.firstChild.remove();
+}
+
+function testEmUnitChangeOnLength()
+{
+  setupTest();
+  gCircleParent.setAttribute("font-size", "10px"); // At first: font-size: 10px
+  var anim = createAnimSetTo("cx", "2em");
+
+  gSvg.setCurrentTime(0);
+  is(gCircle.cx.animVal.value, 20,
+     "Checking animated length=2em after animating");
+
+  gCircleParent.setAttribute("font-size", "20px"); // Change: font-size: 20px
+  // Bug 508206: We should really detect this change and update immediately but
+  // currently we don't until we get sampled again
+  todo_is(gCircle.cx.animVal.value, 40,
+     "Checking animated length=2em after updating context but before sampling");
+
+  gSvg.setCurrentTime(0);
+  is(gCircle.cx.animVal.value, 40,
+     "Checking animated length=2em after updating context and after " +
+     "resampling");
+
+  gCircleParent.removeAttribute("font-size");
+  gCircle.firstChild.remove();
+}
+
+function testPercentUnitChangeOnProp()
+{
+  setupTest();
+  gCircleParent.setAttribute("font-size", "10px"); // At first: font-size: 10px
+  var anim = createAnimSetTo("font-size", "150%");
+
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "font-size"), "15px",
+     "Checking animated font-size=150% after animating");
+
+  gCircleParent.setAttribute("font-size", "20px"); // Change: font-size: 20px
+  gSvg.setCurrentTime(0);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "font-size"), "30px",
+     "Checking animated font-size=150% after updating context");
+
+  gCircleParent.removeAttribute("font-size");
+  gCircle.firstChild.remove();
+}
+
+function testPercentUnitChangeOnLength()
+{
+  setupTest();
+  var oldHeight = gSvg.getAttribute("height");
+  gSvg.setAttribute("height", "100px"); // At first: viewport height: 100px
+  var anim = createAnimSetTo("cy", "100%");
+
+  gSvg.setCurrentTime(0); // Force synchronous sample so animation takes effect
+  // Due to bug 627594 (SVGLength.value for percent value lengths doesn't
+  // reflect updated viewport until reflow) the following will fail.
+  // Check that it does indeed fail so that when that bug is fixed this test
+  // can be updated.
+  todo_is(gCircle.cy.animVal.value, 100,
+     "Checking animated length=100% after animating but before reflow");
+  // force a layout flush (Bug 627594)
+  gSvg.getCTM();
+  // Even after doing a reflow though we'll still fail due to bug 508206
+  // (Relative units used in animation don't update immediately)
+  todo_is(gCircle.cy.animVal.value, 100,
+     "Checking animated length=100% after animating but before resampling");
+  gSvg.setCurrentTime(0);
+  // Now we should be up to date
+  is(gCircle.cy.animVal.value, 100,
+     "Checking animated length=100% after animating");
+
+  gSvg.setAttribute("height", "50px"); // Change: height: 50px
+  // force a layout flush (Bug 627594)
+  gSvg.getCTM();
+  gSvg.setCurrentTime(0); // Bug 508206
+  is(gCircle.cy.animVal.value, 50,
+     "Checking animated length=100% after updating context");
+
+  gSvg.setAttribute("height", oldHeight);
+  gCircle.firstChild.remove();
+}
+
+function testRelativeFontSize()
+{
+  setupTest();
+  gCircleParent.setAttribute("font-size", "10px"); // At first: font-size: 10px
+  var anim = createAnimSetTo("font-size", "larger");
+
+  gSvg.setCurrentTime(0);
+  var fsize = parseInt(SMILUtil.getComputedStyleSimple(gCircle, "font-size"));
+  // CSS 2 suggests a scaling factor of 1.2 so we should be looking at something
+  // around about 12 or so
+  ok(fsize > 10 && fsize < 20,
+    "Checking animated font-size > 10px after animating");
+
+  gCircleParent.setAttribute("font-size", "20px"); // Change: font-size: 20px
+  gSvg.setCurrentTime(0);
+  fsize = parseInt(SMILUtil.getComputedStyleSimple(gCircle, "font-size"));
+  ok(fsize > 20, "Checking animated font-size > 20px after updating context");
+
+  gCircleParent.removeAttribute("font-size");
+  gCircle.firstChild.remove();
+}
+
+function testRelativeFontWeight()
+{
+  setupTest();
+  gCircleParent.setAttribute("font-weight", "100"); // At first: font-weight 100
+  var anim = createAnimSetTo("font-weight", "bolder");
+  // CSS 2: 'bolder': Specifies the next weight that is assigned to a font
+  // that is darker than the inherited one. If there is no such weight, it
+  // simply results in the next darker numerical value (and the font remains
+  // unchanged), unless the inherited value was '900', in which case the
+  // resulting weight is also '900'.
+
+  gSvg.setCurrentTime(0);
+  var weight =
+    parseInt(SMILUtil.getComputedStyleSimple(gCircle, "font-weight"));
+  ok(weight > 100, "Checking animated font-weight > 100 after animating");
+
+  gCircleParent.setAttribute("font-weight", "800"); // Change: font-weight 800
+  gSvg.setCurrentTime(0);
+  weight = parseInt(SMILUtil.getComputedStyleSimple(gCircle, "font-weight"));
+  is(weight, 900,
+     "Checking animated font-weight = 900 after updating context");
+
+  gCircleParent.removeAttribute("font-weight");
+  gCircle.firstChild.remove();
+}
+
+function testRelativeFont()
+{
+  // Test a relative font-size as part of a 'font' spec since the code path
+  // is different in this case
+  // It turns out that, due to the way we store shorthand font properties, we
+  // don't need to worry about marking such values as context-sensitive since we
+  // seem to store them in their relative form. If, however, we change the way
+  // we store shorthand font properties in the future, this will serve as
+  // a useful regression test.
+  setupTest();
+  gCircleParent.setAttribute("font-size", "10px"); // At first: font-size: 10px
+  // We must be sure to set every part of the shorthand property to some
+  // non-context sensitive value because we want to test that even if only the
+  // font-size is relative we will update it appropriately.
+  var anim =
+    createAnimSetTo("font", "normal normal bold larger/normal sans-serif");
+
+  gSvg.setCurrentTime(0);
+  var fsize = parseInt(SMILUtil.getComputedStyleSimple(gCircle, "font-size"));
+  ok(fsize > 10 && fsize < 20,
+    "Checking size of shorthand 'font' > 10px after animating");
+
+  gCircleParent.setAttribute("font-size", "20px"); // Change: font-size: 20px
+  gSvg.setCurrentTime(0);
+  fsize  = parseInt(SMILUtil.getComputedStyleSimple(gCircle, "font-size"));
+  ok(fsize > 20,
+     "Checking size of shorthand 'font' > 20px after updating context");
+
+  gCircleParent.removeAttribute("font-size");
+  gCircle.firstChild.remove();
+}
+
+function testCalcFontSize()
+{
+  setupTest();
+  gCircleParent.setAttribute("font-size", "10px"); // At first: font-size: 10px
+  var anim = createAnimSetTo("font-size", "calc(110% + 0.1em)");
+
+  gSvg.setCurrentTime(0);
+  var fsize = parseInt(SMILUtil.getComputedStyleSimple(gCircle, "font-size"));
+  // Font size should be 1.1 * 10px + 0.1 * 10px = 12
+  is(fsize, 12, "Checking animated calc font-size == 12px after animating");
+
+  gCircleParent.setAttribute("font-size", "20px"); // Change: font-size: 20px
+  gSvg.setCurrentTime(0);
+  fsize = parseInt(SMILUtil.getComputedStyleSimple(gCircle, "font-size"));
+  is(fsize, 24, "Checking animated calc font-size == 24px after updating " +
+                "context");
+
+  gCircleParent.removeAttribute("font-size");
+  gCircle.firstChild.remove();
+}
+
+function testDashArray()
+{
+  // stroke dasharrays don't currently convert units--but if someone ever fixes
+  // that, hopefully this test will fail and remind us not to cache percentage
+  // values in that case
+  setupTest();
+  var oldHeight = gSvg.getAttribute("height");
+  var oldWidth  = gSvg.getAttribute("width");
+  gSvg.setAttribute("height", "100px"); // At first: viewport: 100x100px
+  gSvg.setAttribute("width",  "100px");
+  var anim = createAnimFromTo("stroke-dasharray", "0 5", "0 50%");
+
+  gSvg.setCurrentTime(TIME_AFTER_ANIM_END);
+
+  // Now we should be up to date
+  is(SMILUtil.getComputedStyleSimple(gCircle, "stroke-dasharray"), "0, 50%",
+     "Checking animated stroke-dasharray after animating");
+
+  gSvg.setAttribute("height", "50px"); // Change viewport: 50x50px
+  gSvg.setAttribute("width",  "50px");
+  gSvg.setCurrentTime(TIME_AFTER_ANIM_END);
+  is(SMILUtil.getComputedStyleSimple(gCircle, "stroke-dasharray"), "0, 50%",
+     "Checking animated stroke-dasharray after updating context");
+
+  gSvg.setAttribute("height", oldHeight);
+  gSvg.setAttribute("width",  oldWidth);
+  gCircle.firstChild.remove();
+}
+
+function testClip()
+{
+  setupTest();
+  gCircleParent.setAttribute("font-size", "20px"); // At first: font-size: 20px
+
+  // The clip property only applies to elements that establish a new
+  // viewport so we need to create a nested svg and add animation to that
+  var nestedSVG = document.createElementNS(SVGNS, "svg");
+  nestedSVG.setAttribute("clip", "rect(0px 0px 0px 0px)");
+  gCircleParent.appendChild(nestedSVG);
+
+  var anim = createAnimSetTo("clip", "rect(1em 1em 1em 1em)");
+  // createAnimSetTo will make the animation a child of gCircle so we need to
+  // move it so it targets nestedSVG instead
+  nestedSVG.appendChild(anim);
+
+  gSvg.setCurrentTime(TIME_AFTER_ANIM_END);
+  is(SMILUtil.getComputedStyleSimple(nestedSVG, "clip"),
+     "rect(20px, 20px, 20px, 20px)",
+     "Checking animated clip rect after animating");
+
+  gCircleParent.setAttribute("font-size", "10px"); // Change: font-size: 10px
+  gSvg.setCurrentTime(TIME_AFTER_ANIM_END);
+  is(SMILUtil.getComputedStyleSimple(nestedSVG, "clip"),
+     "rect(10px, 10px, 10px, 10px)",
+     "Checking animated clip rect after updating context");
+
+  gCircleParent.removeAttribute("font-size");
+  gCircleParent.removeChild(nestedSVG);
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilConditionalProcessing.html b/dom/smil/test/test_smilConditionalProcessing.html
new file mode 100644
index 0000000000..302c445b6e
--- /dev/null
+++ b/dom/smil/test/test_smilConditionalProcessing.html
@@ -0,0 +1,93 @@
+<!doctype html>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Test conditional processing tests applied to animations</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg id="svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle r="50" fill="blue" id="circle">
+    <set attributeName="cy" to="100" begin="0s" dur="100s" id="a"/>
+    <set attributeName="cx" to="100" begin="a.end" dur="100s" id="b"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+
+function run() {
+  SpecialPowers.pushPrefEnv({"set": [["intl.accept_languages", "en"]]}, runInternal);
+}
+
+function runInternal() {
+  var svg = document.getElementById("svg"),
+      a = document.getElementById("a"),
+      b = document.getElementById("b"),
+      circle = document.getElementById("circle");
+
+  // Check initial state
+  svg.setCurrentTime(50);
+  is(a.getStartTime(), 0, "a has resolved start time at start");
+  is(circle.cy.animVal.value, 100, "a is in effect at start");
+  is(b.getStartTime(), 100, "b has resolved start time at start");
+
+  // Add a failing conditional processing test
+  a.setAttribute("systemLanguage", "no-such-language");
+  ok(hasUnresolvedStartTime(a),
+     "a has unresolved start time with failing conditional processing test");
+  is(circle.cy.animVal.value, 0,
+     "a is not in effect with failing conditional processing test");
+  ok(hasUnresolvedStartTime(b),
+     "b has unresolved start time with failing conditional processing test on a");
+
+  // Remove failing conditional processing test
+  a.removeAttribute("systemLanguage");
+  is(a.getStartTime(), 0, "a has resolved start time after removing test");
+  is(circle.cy.animVal.value, 100, "a is in effect after removing test");
+  is(b.getStartTime(), 100, "b has resolved start time after removing test on a");
+
+  // Add another failing conditional processing test
+  // According to the spec, if a null string or empty string value is set for
+  // the 'systemLanguage' attribute, the attribute returns "false".
+  a.setAttribute("systemLanguage", "");
+
+  // Fast forward until |a| would have finished
+  var endEventsReceived = 0;
+  a.addEventListener("endEvent", function() { endEventsReceived++; });
+  svg.setCurrentTime(150);
+  is(endEventsReceived, 0,
+     "a does not dispatch end events with failing condition processing test");
+  is(circle.cx.animVal.value, 0,
+     "b is not in effect with failing conditional processing test on a");
+
+  // Make test pass
+  a.setAttribute("systemLanguage", "en");
+  is(circle.cx.animVal.value, 100,
+     "b is in effect with passing conditional processing test on a");
+
+  SimpleTest.finish();
+}
+
+function hasUnresolvedStartTime(anim) {
+  // getStartTime throws INVALID_STATE_ERR when there is no current interval
+  try {
+    anim.getStartTime();
+    return false;
+  } catch (e) {
+    return true;
+  }
+}
+
+window.addEventListener("load", run);
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilContainerBinding.xhtml b/dom/smil/test/test_smilContainerBinding.xhtml
new file mode 100644
index 0000000000..20e1013d4b
--- /dev/null
+++ b/dom/smil/test/test_smilContainerBinding.xhtml
@@ -0,0 +1,101 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for adding and removing animations from a time container</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="-20" cy="20" r="15" fill="blue" id="circle">
+    <set attributeName="cy" to="120" begin="0s; 2s" dur="1s" id="b"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for adding and removing animations from a time container **/
+
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  var svg = getElement("svg");
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  // Create animation and check initial state
+  var anim = createAnim();
+  anim.setAttribute('begin','b.begin+2s; 6s');
+  ok(noStart(anim), "Animation has start time before attaching to document.");
+
+  // Attach animation to container
+  var circle = getElement("circle");
+  circle.appendChild(anim);
+
+  // Check state after attaching
+  is(anim.getStartTime(), 2);
+
+  // Unbind from tree -- the syncbase instance time(s) should become unresolved
+  // but the offset time should remain
+  anim.remove();
+  is(anim.getStartTime(), 6);
+
+  // Rebind and check everything is re-resolved
+  circle.appendChild(anim);
+  is(anim.getStartTime(), 2);
+
+  // Advance document time to t=1s
+  // Now the current interval for b is 2s-3s but the current interval for anim
+  // is still 2s-2.5s based on b's previous interval
+  svg.setCurrentTime(1);
+  is(anim.getStartTime(), 2);
+
+  // Unbind
+  anim.remove();
+  is(anim.getStartTime(), 6);
+
+  // Rebind
+  // At this point only the current interval will be re-added to anim (this is
+  // for consistency since old intervals may or may not have been filtered).
+  // Therefore the start time should be 4s instead of 2s.
+  circle.appendChild(anim);
+  is(anim.getStartTime(), 4);
+
+  SimpleTest.finish();
+}
+
+function createAnim() {
+  const svgns="http://www.w3.org/2000/svg";
+  var anim = document.createElementNS(svgns,'set');
+  anim.setAttribute('attributeName','cx');
+  anim.setAttribute('to','100');
+  anim.setAttribute('dur','0.5s');
+  return anim;
+}
+
+function noStart(elem) {
+  var exceptionCaught = false;
+
+  try {
+    elem.getStartTime();
+  } catch(e) {
+    exceptionCaught = true;
+    is (e.name, "InvalidStateError",
+        "Unexpected exception from getStartTime.");
+    is (e.code, DOMException.INVALID_STATE_ERR,
+        "Unexpected exception code from getStartTime.");
+  }
+
+  return exceptionCaught;
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilCrossContainer.xhtml b/dom/smil/test/test_smilCrossContainer.xhtml
new file mode 100644
index 0000000000..e4d30ef26d
--- /dev/null
+++ b/dom/smil/test/test_smilCrossContainer.xhtml
@@ -0,0 +1,132 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for moving animations between time containers</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svga" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="-20" cy="20" r="15" fill="blue" id="circlea"/>
+</svg>
+<svg id="svgb" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="-20" cy="20" r="15" fill="blue" id="circleb">
+    <set attributeName="cy" to="120" begin="4s" dur="1s" id="syncb"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for moving animations between time containers **/
+
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  var svga = getElement("svga");
+  ok(svga.animationsPaused(), "should be paused by <svg> load handler");
+  is(svga.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+  svga.setCurrentTime(1);
+
+  var svgb = getElement("svgb");
+  ok(svgb.animationsPaused(), "should be paused by <svg> load handler");
+  is(svgb.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+  svgb.setCurrentTime(1);
+
+  // Create animation and check initial state
+  var anim = createAnim();
+  ok(noStart(anim), "Animation has start time before attaching to document");
+
+  // Attach animation to first container
+  var circlea = getElement("circlea");
+  var circleb = getElement("circleb");
+  circlea.appendChild(anim);
+
+  // Check state after attaching
+  is(anim.getStartTime(), 2,
+    "Unexpected start time after attaching animation to target");
+  is(circlea.cx.animVal.value, -20,
+    "Unexpected animated value for yet-to-start animation");
+  is(circleb.cx.animVal.value, -20,
+    "Unexpected animated value for unanimated target");
+
+  // Move animation from first container to second
+  circleb.appendChild(anim);
+
+  // Advance first container and check animation has no effect
+  svga.setCurrentTime(2);
+  is(anim.getStartTime(), 2,
+    "Unexpected start time after moving animation");
+  is(circlea.cx.animVal.value, -20,
+    "Unexpected animated value for non-longer-animated target");
+  is(circleb.cx.animVal.value, -20,
+    "Unexpected animated value for now yet-to-start animation");
+
+  // Advance second container and check the animation only affects it
+  svgb.setCurrentTime(2);
+  is(anim.getStartTime(), 2, "Start time changed after time container seek");
+  is(circlea.cx.animVal.value, -20,
+    "Unanimated target changed after seek on other container");
+  is(circleb.cx.animVal.value, 100, "Animated target not animated after seek");
+
+  // Remove animation so that it belongs to no container and check that
+  // advancing the second container to the next milestone doesn't cause a crash
+  // (when the animation controller goes to run the next milestone sample).
+  anim.remove();
+  svgb.setCurrentTime(3);
+
+  // Do likewise with syncbase relationships
+
+  // Create the syncbase relationship
+  anim.setAttribute('begin', 'syncb.begin');
+
+  // Attach to second time container (where t=3s)
+  circleb.appendChild(anim);
+  is(anim.getStartTime(), 4,
+    "Unexpected start time for cross-time container syncbase dependency");
+
+  // Move to first time container (where t=1s).
+  // Because we're dealing with different time containers and both are paused,
+  // future times are effectively unresolved.
+  circlea.appendChild(anim);
+  ok(noStart(anim), "Unexpected start time for paused time container");
+
+  SimpleTest.finish();
+}
+
+function createAnim() {
+  const svgns="http://www.w3.org/2000/svg";
+  var anim = document.createElementNS(svgns,'set');
+  anim.setAttribute('attributeName','cx');
+  anim.setAttribute('to','100');
+  anim.setAttribute('begin','2s');
+  anim.setAttribute('dur','1s');
+  return anim;
+}
+
+function noStart(elem) {
+  var exceptionCaught = false;
+
+  try {
+    elem.getStartTime();
+  } catch(e) {
+    exceptionCaught = true;
+    is (e.name, "InvalidStateError",
+        "Unexpected exception from getStartTime.");
+    is (e.code, DOMException.INVALID_STATE_ERR,
+        "Unexpected exception code from getStartTime");
+  }
+
+  return exceptionCaught;
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilDynamicDelayedBeginElement.xhtml b/dom/smil/test/test_smilDynamicDelayedBeginElement.xhtml
new file mode 100644
index 0000000000..10da496454
--- /dev/null
+++ b/dom/smil/test/test_smilDynamicDelayedBeginElement.xhtml
@@ -0,0 +1,103 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=699143
+-->
+<head>
+  <title>Test for Bug 699143</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=699143">Mozilla Bug 699143</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+  <svg xmlns="http://www.w3.org/2000/svg">
+    <rect id="r" height="500px" width="500px" fill="blue"/>
+  </svg>
+</div>
+<pre id="test">
+<script type="text/javascript">
+<![CDATA[
+
+/** Test for Bug 699143 **/
+SimpleTest.waitForExplicitFinish();
+
+// Values for 'width' attr on the <rect> above
+const INITIAL_VAL = "500px"
+const FROM_VAL = "20px";
+const TO_VAL   = "80px";
+
+// Helper functions
+
+// This function allows 10ms to pass
+function allowTimeToPass() {
+  var initialDate = new Date();
+  while (new Date() - initialDate < 10) {}
+}
+
+// This function returns a newly created <animate> element for use in this test
+function createAnim() {
+  var a = document.createElementNS('http://www.w3.org/2000/svg', 'animate');
+  a.setAttribute('attributeName', 'width');
+  a.setAttribute('from', FROM_VAL);
+  a.setAttribute('to',   TO_VAL);
+  a.setAttribute('begin', 'indefinite');
+  a.setAttribute('dur', '3s');
+  a.setAttribute('fill', 'freeze');
+  return a;
+}
+
+// Main Functions
+function main() {
+  // In unpatched Firefox builds, we'll only trigger Bug 699143 if we insert
+  // an animation and call beginElement() **after** the document start-time.
+  // Hence, we use executeSoon here to allow some time to pass.  (And then
+  // we'll use a short busy-loop, for good measure.)
+  SimpleTest.executeSoon(runTest);
+}
+
+function runTest() {
+  var svg = SMILUtil.getSVGRoot();
+
+  // In case our executeSoon fired immediately, we force a very small amount
+  // of time to pass here, using a 10ms busy-loop.
+  allowTimeToPass();
+
+  is(svg.getCurrentTime(), 0,
+     "even though we've allowed time to pass, we shouldn't have bothered " +
+     "updating the current time, since there aren't any animation elements");
+
+  // Insert an animation elem (should affect currentTime but not targeted attr)
+  var r = document.getElementById("r");
+  var a = createAnim();
+  r.appendChild(a);
+  isnot(svg.getCurrentTime(), 0,
+       "insertion of first animation element should have triggered a " +
+       "synchronous sample and updated our current time");
+  is(r.width.animVal.valueAsString, INITIAL_VAL,
+     "inserted animation shouldn't have affected its targeted attribute, " +
+     "since it doesn't have any intervals yet");
+
+  // Trigger the animation & be sure it takes effect
+  a.beginElement();
+  is(r.width.animVal.valueAsString, FROM_VAL,
+     "beginElement() should activate our animation & set its 'from' val");
+
+  // Rewind to time=0 & check target attr, to be sure beginElement()-generated
+  // interval starts later than that.
+  svg.setCurrentTime(0);
+  is(r.width.animVal.valueAsString, INITIAL_VAL,
+     "after rewinding to 0, our beginElement()-generated interval " +
+     "shouldn't be active yet");
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilExtDoc.xhtml b/dom/smil/test/test_smilExtDoc.xhtml
new file mode 100644
index 0000000000..0323cbfb77
--- /dev/null
+++ b/dom/smil/test/test_smilExtDoc.xhtml
@@ -0,0 +1,80 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=628888
+-->
+<head>
+  <title>Test for Bug 628888 - Animations in external document sometimes don't run</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body style="margin:0px">
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=628888">Mozilla Bug 628888</a>
+<p id="display"></p>
+<div id="content" style="background: red; width: 50px; height: 50px"/>
+  
+<pre id="test">
+<script type="application/javascript">
+<![CDATA[
+
+/* Test for Bug 628888 - Animations in external document sometimes don't run
+ *
+ * This bug concerns a condition where an external document is loaded after the
+ * page show event is dispatched, leaving the external document paused.
+ *
+ * To reproduce the bug we attach an external document with animation after the
+ * page show event has fired.
+ *
+ * However, it is difficult to test if the animation is playing or not since we
+ * don't receive events from animations running in an external document.
+ *
+ * Our approach is to simply render the result to a canvas (which requires
+ * elevated privileges and that is why we are using a MochiTest rather
+ * than a reftest) and poll one of the pixels to see if it changes colour.
+ *
+ * This should mean the test succeeds quickly but fails slowly.
+ */
+
+const POLL_INTERVAL     = 100;   // ms
+const POLL_TIMEOUT      = 10000; // ms
+var accumulatedWaitTime = 0;
+
+function pageShow()
+{
+  var content = document.getElementById("content");
+  content.style.filter = "url(smilExtDoc_helper.svg#filter)";
+  window.setTimeout(checkResult, 0);
+}
+
+function checkResult()
+{
+  var content = document.getElementById("content");
+  var bbox = content.getBoundingClientRect();
+
+  var canvas = SpecialPowers.snapshotRect(window, bbox);
+  var ctx = canvas.getContext("2d");
+
+  var imgd = ctx.getImageData(bbox.width/2, bbox.height/2, 1, 1);
+  var isGreen = (imgd.data[0] == 0) &&
+                (imgd.data[1] == 255) &&
+                (imgd.data[2] == 0);
+  if (isGreen) {
+    ok(true, "Filter is animated as expected");
+  } else if (accumulatedWaitTime >= POLL_TIMEOUT) {
+    ok(false, "No animation detected after waiting " + POLL_TIMEOUT + "ms");
+  } else {
+    accumulatedWaitTime += POLL_INTERVAL;
+    window.setTimeout(checkResult, POLL_INTERVAL);
+    return;
+  }
+  // Hide our content since mochitests normally try to be visually "quiet"
+  content.style.display = 'none';
+  SimpleTest.finish();
+}
+window.addEventListener('pageshow', pageShow);
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestFlakyTimeout("untriaged");
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilFillMode.xhtml b/dom/smil/test/test_smilFillMode.xhtml
new file mode 100644
index 0000000000..ed270863bd
--- /dev/null
+++ b/dom/smil/test/test_smilFillMode.xhtml
@@ -0,0 +1,86 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL fill modes</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="-100" cy="20" r="15" fill="blue" id="circle"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL fill modes **/
+
+/* Global Variables */
+const svgns="http://www.w3.org/2000/svg";
+var svg = document.getElementById("svg");
+var circle = document.getElementById('circle');
+
+SimpleTest.waitForExplicitFinish();
+
+function createAnim() {
+  var anim = document.createElementNS(svgns,'animate');
+  anim.setAttribute('attributeName','cx');
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('begin','0s');
+  anim.setAttribute('values', '10; 20');
+  return circle.appendChild(anim);
+}
+
+function main() {
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var tests =
+    [ testSetLaterA,
+      testSetLaterB,
+      testRemoveLater ];
+  for (var i = 0; i < tests.length; i++) {
+    var anim = createAnim();
+    svg.setCurrentTime(0);
+    tests[i](anim);
+    anim.remove();
+  }
+  SimpleTest.finish();
+}
+
+function checkSample(time, expectedValue) {
+  svg.setCurrentTime(time);
+  is(circle.cx.animVal.value, expectedValue,
+     "Updated fill mode not applied to animation");
+}
+
+// Test that we can update the fill mode after an interval has played and it
+// will be updated correctly.
+function testSetLaterA(anim) {
+  checkSample(5, -100);
+  anim.setAttribute('fill', 'freeze');
+  is(circle.cx.animVal.value, 20,
+    "Fill not applied for retrospectively set fill mode");
+}
+
+function testSetLaterB(anim) {
+  anim.setAttribute('fill', 'freeze');
+  checkSample(5, 20);
+}
+
+function testRemoveLater(anim) {
+  anim.setAttribute('fill', 'freeze');
+  checkSample(5, 20);
+  anim.setAttribute('fill', 'remove');
+  is(circle.cx.animVal.value, -100,
+    "Fill not removed for retrospectively set fill mode");
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilGetSimpleDuration.xhtml b/dom/smil/test/test_smilGetSimpleDuration.xhtml
new file mode 100644
index 0000000000..e36922c34a
--- /dev/null
+++ b/dom/smil/test/test_smilGetSimpleDuration.xhtml
@@ -0,0 +1,84 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for getSimpleDuration Behavior </title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px">
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animate attributeName="cx" attributeType="XML" 
+      from="20" to="100" begin="1s" id="anim"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for getSimpleDuration Behavior  **/
+
+/* Global Variables */
+var svg = document.getElementById("svg");
+
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  var anim = document.getElementById("anim");
+
+  /* Check initial state */
+  checkForException(anim, "dur not set");
+
+  /* Check basic operation */
+  anim.setAttribute("dur", "1s");
+  is(anim.getSimpleDuration(), 1);
+  anim.setAttribute("dur", ".15s");
+  isfuzzy(anim.getSimpleDuration(), 0.15, 0.001);
+  anim.setAttribute("dur", "1.5s");
+  is(anim.getSimpleDuration(), 1.5);
+
+  /* Check exceptional states */
+  anim.setAttribute("dur", "0s");
+  checkForException(anim, "dur=0s");
+  anim.setAttribute("dur", "-1s");
+  checkForException(anim, "dur=-1s");
+  anim.setAttribute("dur", "indefinite");
+  checkForException(anim, "dur=indefinite");
+  anim.setAttribute("dur", "media");
+  checkForException(anim, "dur=media");
+  anim.setAttribute("dur", "abc");
+  checkForException(anim, "dur=abc");
+  anim.removeAttribute("dur");
+  checkForException(anim, "dur not set");
+
+  /* Check range/syntax */
+  anim.setAttribute("dur", "100ms");
+  isfuzzy(anim.getSimpleDuration(), 0.1, 0.001);
+  anim.setAttribute("dur", "24h");
+  is(anim.getSimpleDuration(), 60 * 60 * 24);
+
+  SimpleTest.finish();
+}
+
+function checkForException(anim, descr) {
+  var gotException = false;
+  try {
+    var dur = anim.getSimpleDuration();
+  } catch(e) {
+    is (e.name, "NotSupportedError",
+        "Wrong exception from getSimpleDuration");
+    is (e.code, DOMException.NOT_SUPPORTED_ERR,
+        "Wrong exception from getSimpleDuration");
+    gotException = true;
+  }
+  ok(gotException,
+     "Exception not thrown for indefinite simple duration when " + descr);
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilGetStartTime.xhtml b/dom/smil/test/test_smilGetStartTime.xhtml
new file mode 100644
index 0000000000..f854dd7cd9
--- /dev/null
+++ b/dom/smil/test/test_smilGetStartTime.xhtml
@@ -0,0 +1,103 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for getStartTime Behavior </title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animate attributeName="cx" attributeType="XML" 
+      from="20" to="100" begin="indefinite" dur="1s" id="anim"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for getStartTime Behavior  **/
+
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  var svg = document.getElementById("svg");
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var anim = document.getElementById("anim");
+  // indefinite 
+  var exceptionCaught = false;
+  try {
+    anim.getStartTime();
+  } catch(e) {
+    exceptionCaught = true;
+    is(e.name, "InvalidStateError",
+       "Unexpected exception from getStartTime.");
+    is(e.code, DOMException.INVALID_STATE_ERR,
+       "Unexpected exception code from getStartTime.");
+  }
+  ok(exceptionCaught, "No exception thrown for indefinite start time.");
+
+  // 1s
+  anim.setAttribute("begin", "1s");
+  is(anim.getStartTime(), 1, "Unexpected start time with begin=1s");
+
+  // We have to be careful here when choosing a negative time that we choose
+  // a time that will create an interval that reaches past t=0 as SMIL has
+  // special rules for throwing away intervals that end before t=0
+  anim.setAttribute("begin", "-0.5s");
+  is(anim.getStartTime(), -0.5, "Unexpected start time with begin=-0.5s");
+
+  // Once the animation has begun, the begin time is fixed so we need to end the
+  // element (or advance the timeline) to override the previous start time
+  anim.endElement();
+
+  // However, now we have an end instance, and the SMIL model dictates that if
+  // we have end instances and no end event conditions and all end instances are
+  // before our next begin, there's no valid interval. To overcome this we add
+  // an indefinite end.
+  anim.setAttribute("end", "indefinite");
+
+  // Now test over the lifetime of the animation when there are multiple
+  // intervals
+  anim.setAttribute("begin", "1s; 3s");
+  is(anim.getStartTime(), 1, "Unexpected start time before first interval");
+  
+  svg.setCurrentTime(1);
+  is(anim.getStartTime(), 1,
+     "Unexpected start time at start of first interval");
+
+  svg.setCurrentTime(1.5);
+  is(anim.getStartTime(), 1, "Unexpected start time during first interval");
+
+  svg.setCurrentTime(2);
+  is(anim.getStartTime(), 3, "Unexpected start time after first interval");
+
+  svg.setCurrentTime(3);
+  is(anim.getStartTime(), 3, "Unexpected start time during second interval");
+
+  svg.setCurrentTime(4);
+  exceptionCaught = false;
+  try {
+    anim.getStartTime();
+  } catch(e) {
+    exceptionCaught = true;
+    is(e.name, "InvalidStateError",
+       "Unexpected exception from getStartTime.");
+    is(e.code, DOMException.INVALID_STATE_ERR,
+       "Unexpected exception code from getStartTime.");
+  }
+  ok(exceptionCaught, "No exception thrown for in postactive state.");
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilHyperlinking.xhtml b/dom/smil/test/test_smilHyperlinking.xhtml
new file mode 100644
index 0000000000..49e9e7f7b0
--- /dev/null
+++ b/dom/smil/test/test_smilHyperlinking.xhtml
@@ -0,0 +1,229 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for hyperlinking</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display:none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="-100" cy="20" r="15" fill="blue" id="circle"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL keySplines **/
+
+/* Global Variables */
+const SVGNS="http://www.w3.org/2000/svg";
+var gSvg = document.getElementById("svg");
+var gAnim;
+
+var gTestStages =
+  [ testActive,
+    testSeekToFirst,
+    testKickStart,
+    testKickStartWithUnresolved,
+    testFiltering
+  ];
+
+SimpleTest.waitForExplicitFinish();
+
+function continueTest()
+{
+  if (!gTestStages.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  window.location.hash = "";
+  if (gAnim) {
+    gAnim.remove();
+  }
+  gAnim = createAnim();
+  gSvg.setCurrentTime(0);
+  gTestStages.shift()();
+}
+
+function createAnim() {
+  var anim = document.createElementNS(SVGNS,'animate');
+  anim.setAttribute('attributeName','cx');
+  anim.setAttribute('from','0');
+  anim.setAttribute('to','100');
+  anim.setAttribute('dur','1s');
+  anim.setAttribute('begin','indefinite');
+  anim.setAttribute('id','anim');
+  return document.getElementById('circle').appendChild(anim);
+}
+
+// Traversing a hyperlink, condition 1:
+// 
+// "If the target element is active, seek the document time back to the
+// (current) begin time of the element. If there are multiple begin times, use
+// the begin time that corresponds to the current "begin instance"."
+//
+function testActive() {
+  gAnim.setAttribute('begin','2s; 4s');
+  gSvg.setCurrentTime(2.5);
+  fireLink(rewindActiveInterval1);
+}
+
+function rewindActiveInterval1() {
+  is(gSvg.getCurrentTime(), 2,
+     "Unexpected time after activating link to animation in the middle of " +
+     "first active interval");
+
+  // Seek to second interval
+  gSvg.setCurrentTime(4.5);
+  fireLink(rewindActiveInterval2);
+}
+
+function rewindActiveInterval2() {
+  is(gSvg.getCurrentTime(), 4,
+     "Unexpected time after activating link to animation in the middle of " +
+     "second active interval");
+
+  // Try a negative time
+  gAnim.setAttribute("begin", "-0.5");
+  gSvg.setCurrentTime(0.2);
+  fireLink(rewindActiveIntervalAtZero);
+}
+
+function rewindActiveIntervalAtZero() {
+  is(gSvg.getCurrentTime(), 0,
+     "Unexpected time after activating link to animation in the middle of " +
+     "an active interval that overlaps zero");
+
+  continueTest();
+}
+
+// Traversing a hyperlink, condition 2:
+// 
+// "Else if the target element begin time is resolved (i.e., there is any
+// resolved time in the list of begin times, or if the begin time was forced by
+// an earlier hyperlink or a beginElement() method call), seek the document time
+// (forward or back, as needed) to the earliest resolved begin time of the
+// target element. Note that the begin time may be resolved as a result of an
+// earlier hyperlink, DOM or event activation. Once the begin time is resolved,
+// hyperlink traversal always seeks."
+//
+function testSeekToFirst() {
+  // Seek forwards
+  gAnim.setAttribute('begin','2s');
+  gSvg.setCurrentTime(0);
+  fireLink(forwardToInterval1);
+}
+
+function forwardToInterval1() {
+  is(gSvg.getCurrentTime(), 2,
+     "Unexpected time after activating link to animation scheduled to start " +
+     "the future");
+
+  // Seek backwards
+  gSvg.setCurrentTime(3.5);
+  fireLink(backwardToInterval1);
+}
+
+function backwardToInterval1() {
+  is(gSvg.getCurrentTime(), 2,
+     "Unexpected time after activating link to animation that ran in the past");
+
+  // What if the first begin instance is negative?
+  gAnim.setAttribute('begin','-0.5s');
+  gSvg.setCurrentTime(1);
+  fireLink(backwardToZero);
+}
+
+function backwardToZero() {
+  is(gSvg.getCurrentTime(), 0,
+     "Unexpected time after activating link to animation that ran in the " +
+     "past with a negative time");
+
+  continueTest();
+}
+
+// Traversing a hyperlink, condition 3:
+// 
+// "Else (animation begin time is unresolved) just resolve the target animation
+// begin time at current document time. Disregard the sync-base or event base of
+// the animation, and do not "back-propagate" any timing logic to resolve the
+// child, but rather treat it as though it were defined with begin="indefinite"
+// and just resolve begin time to the current document time."
+//
+function testKickStart() {
+  gSvg.setCurrentTime(1);
+  fireLink(startedAt1s);
+}
+
+function startedAt1s() {
+  is(gSvg.getCurrentTime(), 1,
+     "Unexpected time after kick-starting animation with indefinite start " +
+     "by hyperlink");
+  is(gAnim.getStartTime(), 1,
+     "Unexpected start time for kick-started animation");
+
+  continueTest();
+}
+
+function testKickStartWithUnresolved() {
+  gAnim.setAttribute("begin", "circle.click");
+  gSvg.setCurrentTime(3);
+  fireLink(startedAt3s);
+}
+
+function startedAt3s() {
+  is(gSvg.getCurrentTime(), 3,
+     "Unexpected time after kick-starting animation with unresolved start " +
+     "by hyperlink");
+  is(gAnim.getStartTime(), 3,
+     "Unexpected start time for kick-started animation with unresolved begin " +
+     "condition");
+
+  continueTest();
+}
+
+function testFiltering() {
+  gAnim.setAttribute('begin','-3s; 1s; 2s; 3s; 4s; 5s; 6s; 7s; 8s; 9s; 10s');
+  gSvg.setCurrentTime(12);
+  fireLink(rewindToFirst);
+}
+
+function rewindToFirst() {
+  is(gSvg.getCurrentTime(), 1,
+     "Unexpected time after triggering animation with a hyperlink after " +
+     "numerous intervals have passed");
+
+  continueTest();
+}
+
+function fireLink(callback) {
+  // First we need to reset the hash because otherwise the redundant hashchange
+  // events will be suppressed
+  if (window.location.hash === '') {
+    fireLinkPart2(callback);
+  } else {
+    window.location.hash = '';
+    window.addEventListener("hashchange",
+      function() {
+        window.setTimeout(fireLinkPart2, 0, callback);
+      }, {once: true});
+  }
+}
+
+function fireLinkPart2(callback) {
+  window.addEventListener("hashchange",
+    function() {
+      window.setTimeout(callback, 0);
+    }, {once: true});
+  window.location.hash = '#anim';
+}
+
+window.addEventListener("load", continueTest);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilInvalidValues.html b/dom/smil/test/test_smilInvalidValues.html
new file mode 100644
index 0000000000..29ddfad39a
--- /dev/null
+++ b/dom/smil/test/test_smilInvalidValues.html
@@ -0,0 +1,122 @@
+<!doctype html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=941315
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test invalid values cause the model to be updated (bug 941315)</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=941315">Mozilla Bug 941315</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg width="100%" height="1" onload="this.pauseAnimations()">
+  <rect>
+    <animate id="a" dur="100s"/>
+    <animate id="b" dur="5s" begin="a.end"/>
+  </rect>
+  <circle cx="-100" cy="20" r="15" fill="blue" id="circle"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+  var a = $('a'),
+      b = $('b');
+
+  // Animation doesn't start until onload
+  SimpleTest.waitForExplicitFinish();
+  window.addEventListener("load", runTests);
+
+  // Make testing getStartTime easier
+  SVGAnimationElement.prototype.safeGetStartTime = function() {
+    try {
+      return this.getStartTime();
+    } catch(e) {
+      if (e.name == "InvalidStateError" &&
+          e.code == DOMException.INVALID_STATE_ERR) {
+        return 'none';
+      } else {
+        ok(false, "Unexpected exception: " + e);
+        return null;
+      }
+    }
+  };
+
+  function runTests() {
+    [testSimpleDuration, testSimpleDuration2, testMin, testMax, testRepeatDur, testRepeatCount]
+      .forEach(function(test) {
+        is(b.getStartTime(), 100, "initial state before running " + test.name);
+        test();
+        is(b.getStartTime(), 100, "final state after running " + test.name);
+      });
+    SimpleTest.finish();
+  }
+
+  function testSimpleDuration() {
+    // Verify a valid value updates as expected
+    a.setAttribute("dur", "50s");
+    is(b.safeGetStartTime(), 50, "valid simple duration");
+
+    // Check an invalid value also causes the model to be updated
+    a.setAttribute("dur", "abc"); // -> indefinite
+    is(b.safeGetStartTime(), "none", "invalid simple duration");
+
+    // Restore state
+    a.setAttribute("dur", "100s");
+  }
+
+  function testSimpleDuration2() {
+    // Check an invalid value causes the model to be updated
+    a.setAttribute("dur", "-.1s"); // -> indefinite
+    is(b.safeGetStartTime(), "none", "invalid simple duration");
+
+    // Restore state
+    a.setAttribute("dur", "100s");
+  }
+
+  function testMin() {
+    a.setAttribute("min", "200s");
+    is(b.safeGetStartTime(), 200, "valid min duration");
+
+    a.setAttribute("min", "abc"); // -> indefinite
+    is(b.safeGetStartTime(), 100, "invalid min duration");
+
+    a.removeAttribute("min");
+  }
+
+  function testMax() {
+    a.setAttribute("max", "50s");
+    is(b.safeGetStartTime(), 50, "valid max duration");
+
+    a.setAttribute("max", "abc"); // -> indefinite
+    is(b.safeGetStartTime(), 100, "invalid max duration");
+
+    a.removeAttribute("max");
+  }
+
+  function testRepeatDur() {
+    a.setAttribute("repeatDur", "200s");
+    is(b.safeGetStartTime(), 200, "valid repeatDur duration");
+
+    a.setAttribute("repeatDur", "abc"); // -> indefinite
+    is(b.safeGetStartTime(), 100, "invalid repeatDur duration");
+
+    a.removeAttribute("repeatDur");
+  }
+
+  function testRepeatCount() {
+    a.setAttribute("repeatCount", "2");
+    is(b.safeGetStartTime(), 200, "valid repeatCount duration");
+
+    a.setAttribute("repeatCount", "abc"); // -> indefinite
+    is(b.safeGetStartTime(), 100, "invalid repeatCount duration");
+
+    a.removeAttribute("repeatCount");
+  }
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilKeySplines.xhtml b/dom/smil/test/test_smilKeySplines.xhtml
new file mode 100644
index 0000000000..c12f6f1e09
--- /dev/null
+++ b/dom/smil/test/test_smilKeySplines.xhtml
@@ -0,0 +1,296 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL keySplines</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="-100" cy="20" r="15" fill="blue" id="circle"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL keySplines **/
+
+/* Global Variables */
+const svgns="http://www.w3.org/2000/svg";
+var svg = document.getElementById("svg");
+var circle = document.getElementById('circle');
+
+SimpleTest.waitForExplicitFinish();
+
+function createAnim() {
+  var anim = document.createElementNS(svgns,'animate');
+  anim.setAttribute('attributeName','cx');
+  anim.setAttribute('dur','10s');
+  anim.setAttribute('begin','0s');
+  anim.setAttribute('fill', 'freeze');
+  return circle.appendChild(anim);
+}
+
+function main() {
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var tests =
+    [ testSimpleA, // these first four are from SVG 1.1
+      testSimpleB,
+      testSimpleC,
+      testSimpleD,
+      testSimpleE, // bug 501569
+      testMultipleIntervalsA,
+      testMultipleIntervalsB,
+      testMultipleIntervalsC,
+      testOneValue,
+      testFromTo,
+      testWrongNumSplines,
+      testToAnimation,
+      testOkSyntax,
+      testBadSyntaxA,
+      testBadSyntaxB
+    ];
+  for (var i = 0; i < tests.length; i++) {
+    var anim = createAnim();
+    svg.setCurrentTime(0);
+    tests[i](anim);
+    anim.remove();
+  }
+  SimpleTest.finish();
+}
+
+function checkSample(time, expectedValue) {
+  svg.setCurrentTime(time);
+  is(circle.cx.animVal.value, expectedValue);
+}
+
+function checkSampleRough(time, expectedValue, precision) {
+  const defaultPrecision = 0.00001;
+  if (typeof precision == "undefined") {
+    precision = defaultPrecision;
+  }
+  svg.setCurrentTime(time);
+  var diff = Math.abs(expectedValue - circle.cx.animVal.value);
+  ok(diff <= precision,
+    "Unexpected sample value got " + circle.cx.animVal.value
+      + ", expected " + expectedValue + " [error is " + diff
+      + ", tolerance is " + precision + "]");
+}
+
+/*
+ * These first four tests are the examples given in SVG 1.1, section 19.2.7
+ */
+
+function testSimpleA(anim) {
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('values', '10; 20');
+  anim.setAttribute('keyTimes', '0; 1');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '0 0 1 1');
+  checkSample(0, 10);
+  checkSample(1, 12.5);
+  checkSample(2, 15);
+  checkSample(3, 17.5);
+  checkSample(4, 20);
+}
+
+function testSimpleB(anim) {
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('values', '10; 20');
+  anim.setAttribute('keyTimes', '0; 1');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '.5 0 .5 1');
+  checkSample(0, 10);
+  checkSampleRough(1, 11.058925);
+  checkSample(2, 15);
+  checkSampleRough(3, 18.941075);
+  checkSample(4, 20);
+}
+
+function testSimpleC(anim) {
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('values', '10; 20');
+  anim.setAttribute('keyTimes', '0; 1');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '0 .75 .25 1');
+  checkSample(0, 10);
+  checkSampleRough(1, 18.101832);
+  checkSampleRough(2, 19.413430);
+  checkSampleRough(3, 19.886504);
+  checkSample(4, 20);
+}
+
+function testSimpleD(anim) {
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('values', '10; 20');
+  anim.setAttribute('keyTimes', '0; 1');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '1 0 .25 .25');
+  checkSample(0, 10);
+  checkSampleRough(1, 10.076925);
+  checkSampleRough(2, 10.644369);
+  checkSampleRough(3, 16.908699);
+  checkSample(4, 20);
+}
+
+// Bug 501569 -- SMILKeySpline(1, 0, 0, 1) miscalculates values just under 0.5
+function testSimpleE(anim) {
+  anim.setAttribute('dur','10s');
+  anim.setAttribute('values', '0; 10');
+  anim.setAttribute('keyTimes', '0; 1');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '1 0 0 1');
+  checkSample(0, 0);
+  checkSampleRough(0.001, 0);
+  checkSampleRough(4.95, 3.409174);
+  checkSampleRough(4.98, 3.819443);
+  checkSampleRough(4.99, 4.060174);
+  checkSampleRough(4.999, 4.562510);
+  checkSample(5, 5);
+  checkSampleRough(5.001, 5.437490);
+  checkSampleRough(5.01, 5.939826);
+  checkSampleRough(5.015, 6.075002);
+  checkSampleRough(5.02, 6.180557);
+  checkSampleRough(9.9999, 10);
+  checkSample(10, 10);
+}
+
+function testMultipleIntervalsA(anim) {
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('values', '10; 20; 30');
+  anim.setAttribute('keyTimes', '0; 0.25; 1');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '0 0 1 1; .5 0 .5 1;');
+  checkSample(0.5, 15);
+  checkSampleRough(0.999, 20, 0.02);
+  checkSample(1, 20);
+  checkSampleRough(1.001, 20, 0.05);
+  checkSample(2.5, 25);
+  checkSampleRough(3.25, 29, 0.1);
+}
+
+function testMultipleIntervalsB(anim) {
+  // as above but without keyTimes
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('values', '10; 20; 30');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '0 0 1 1; .5 0 .5 1;');
+  checkSample(1, 15);
+  checkSampleRough(1.999, 20, 0.01);
+  checkSample(2, 20);
+  checkSampleRough(2.001, 20, 0.01);
+  checkSample(3, 25);
+  checkSampleRough(3.5, 29, 0.1);
+}
+
+function testMultipleIntervalsC(anim) {
+  // test some unusual (but valid) syntax
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('values', '10; 20; 30');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', ' 0 .75 0.25 1 ; 1, 0 ,.25 .25  \t');
+  checkSampleRough(3.5, 26.9, 0.2);
+}
+
+function testOneValue(anim) {
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('values', '5');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '0 0 1 1');
+  checkSample(0, 5);
+  checkSample(1.5, 5);
+}
+
+function testFromTo(anim) {
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('from', '10');
+  anim.setAttribute('to', '20');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '.5 0 .5 1');
+  checkSample(0, 10);
+  checkSampleRough(1, 11, 0.1);
+}
+
+function testWrongNumSplines(anim) {
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('from', '10');
+  anim.setAttribute('to', '20');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '.5 0 .5 1; 0 0 1 1');
+  // animation is in error, should do nothing
+  checkSample(1.5, -100);
+}
+
+function testToAnimation(anim) {
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('to', '20');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', '.5 0 .5 1');
+  checkSample(0, -100);
+  checkSampleRough(1, -87.3, 0.1);
+}
+
+function testOkSyntax(anim) {
+  var okStrs = ['0,0,0,0', // all commas
+                '  0 0   , 0  ,0  ', // mix of separators
+                '0 0 0 0;', // trailing semi-colon
+                '0 0 0 0 ;']; //   "      "
+
+  for (var i = 0; i < okStrs.length; i++) {
+    testAnim = createAnim();
+    testAnim.setAttribute('dur','4s');
+    testAnim.setAttribute('from', '0');
+    testAnim.setAttribute('to', '20');
+    testAnim.setAttribute('calcMode', 'spline');
+    testAnim.setAttribute('keySplines', okStrs[i]);
+    checkSample(4, 20);
+    testAnim.remove();
+  }
+}
+
+function testBadSyntaxA(anim) {
+  var badStrs = ['', // empty
+                 '    ', // whitespace only
+                 '0,1.1,0,0', // bad range
+                 '0,0,0,-0.1', // "   "
+                 '  0 0   , 0  0   ,', // stray comma
+                 '1-1 0 0', // path-style separators
+                 '0 0 0', // wrong number of values
+                 '0 0 0 0 0', //  "     "
+                 '0 0 0 0 0 0 0 0', //  "     "
+                 '0 0 0; 0 0 0 0', //  "     "
+                 '0 0 0; 0', // mis-placed semi-colon
+                 ';0 0 0 0']; //    "    "
+
+  for (var i = 0; i < badStrs.length; i++) {
+    testAnim = createAnim();
+    testAnim.setAttribute('dur','4s');
+    testAnim.setAttribute('from', '0');
+    testAnim.setAttribute('to', '20');
+    testAnim.setAttribute('calcMode', 'spline');
+    testAnim.setAttribute('keySplines', badStrs[i]);
+    checkSample(4, -100);
+    testAnim.remove();
+  }
+}
+
+function testBadSyntaxB(anim) {
+  // test some illegal syntax
+  anim.setAttribute('dur','4s');
+  anim.setAttribute('values', '10; 20; 30');
+  anim.setAttribute('calcMode', 'spline');
+  anim.setAttribute('keySplines', ' 0 .75 0.25 1 ; 1, A0 ,.25 .25  \t');
+  // animation is in error, should do nothing
+  checkSample(3.5, -100);
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilKeyTimes.xhtml b/dom/smil/test/test_smilKeyTimes.xhtml
new file mode 100644
index 0000000000..43d3c91895
--- /dev/null
+++ b/dom/smil/test/test_smilKeyTimes.xhtml
@@ -0,0 +1,391 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL keyTimes</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank"
+  href="https://bugzilla.mozilla.org/show_bug.cgi?id=557885">Mozilla Bug
+  557885</a>
+<p id="display"></p>
+<div id="content">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px">
+  <circle cx="-100" cy="20" r="15" fill="blue" id="circle"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL keyTimes **/
+
+var gSvg = document.getElementById("svg");
+SimpleTest.waitForExplicitFinish();
+
+function main()
+{
+  gSvg.pauseAnimations();
+
+  var testCases = Array();
+
+  // Simple case
+  testCases.push({
+    'attr' : { 'values': '0; 50; 100',
+               'keyTimes': '0; .8; 1' },
+    'times': [ [ 4, 25 ],
+               [ 8, 50 ],
+               [ 9, 75 ],
+               [ 10, 100 ] ]
+  });
+
+  // Parsing tests
+  testCases.push(parseOk('  0 ; .8;1 ')); // extra whitespace
+  testCases.push(parseNotOk(';0; .8; 1')); // leading semi-colon
+  testCases.push(parseNotOk('; .8; 1')); // leading semi-colon
+  testCases.push(parseOk('0; .8; 1;')); // trailing semi-colon
+  testCases.push(parseNotOk('')); // empty string
+  testCases.push(parseNotOk('  ')); // empty string
+  testCases.push(parseNotOk('0; .8')); // too few values
+  testCases.push(parseNotOk('0; .8; .9; 1')); // too many values
+  testCases.push(parseNotOk('0; 1; .8')); // non-increasing
+  testCases.push(parseNotOk('0; .8; .9')); // final value non-1 with
+                                           // calcMode=linear
+  testCases.push(parseOk('0; .8; .9', { 'calcMode': 'discrete' }));
+  testCases.push(parseNotOk('0.01; .8; 1')); // first value not 0
+  testCases.push(parseNotOk('0.01; .8; 1', { 'calcMode': 'discrete' }));
+                                            // first value not 0
+  testCases.push(parseNotOk('0; .8; 1.1')); // out of range
+  testCases.push(parseNotOk('-0.1; .8; 1')); // out of range
+
+
+  // 2 values
+  testCases.push({
+    'attr' : { 'values': '0; 50',
+               'keyTimes': '0; 1' },
+    'times': [ [ 6, 30 ] ]
+  });
+
+  // 1 value
+  testCases.push({
+    'attr' : { 'values': '50',
+               'keyTimes': ' 0' },
+    'times': [ [ 7, 50 ] ]
+  });
+
+  // 1 bad value
+  testCases.push({
+    'attr' : { 'values': '50',
+               'keyTimes': '0.1' },
+    'times': [ [ 0, -100 ] ]
+  });
+
+  // 1 value, calcMode=discrete
+  testCases.push({
+    'attr' : { 'values': '50',
+               'calcMode': 'discrete',
+               'keyTimes': ' 0' },
+    'times': [ [ 7, 50 ] ]
+  });
+
+  // 1 bad value, calcMode=discrete
+  testCases.push({
+    'attr' : { 'values': '50',
+               'calcMode': 'discrete',
+               'keyTimes': '0.1' },
+    'times': [ [ 0, -100 ] ]
+  });
+
+  // from-to
+  testCases.push({
+    'attr' : { 'from': '10',
+               'to': '20',
+               'keyTimes': '0.0; 1.0' },
+    'times': [ [ 3.5, 13.5 ] ]
+  });
+
+  // from-to calcMode=discrete
+  testCases.push({
+    'attr' : { 'from': '10',
+               'to': '20',
+               'calcMode': 'discrete',
+               'keyTimes': '0.0; 0.7' },
+    'times': [ [ 0, 10 ],
+               [ 6.9, 10 ],
+               [ 7.0, 20 ],
+               [ 10.0, 20 ],
+               [ 11.0, 20 ] ]
+  });
+
+  // from-to calcMode=discrete one keyTime only
+  testCases.push({
+    'attr' : { 'values': '20',
+               'calcMode': 'discrete',
+               'keyTimes': '0' },
+    'times': [ [ 0, 20 ],
+               [ 6.9, 20 ],
+               [ 7.0, 20 ],
+               [ 10.0, 20 ],
+               [ 11.0, 20 ] ]
+  });
+
+  // from-to calcMode=discrete one keyTime, mismatches no. values
+  testCases.push({
+    'attr' : { 'values': '10; 20',
+               'calcMode': 'discrete',
+               'keyTimes': '0' },
+    'times': [ [ 0, -100 ] ]
+  });
+
+  // to
+  testCases.push({
+    'attr' : { 'to': '100',
+               'keyTimes': '0.0; 1.0' },
+    'times': [ [ 0, -100 ],
+               [ 7, 40 ] ]
+  });
+
+  // to -- bad number of keyTimes (too many)
+  testCases.push({
+    'attr' : { 'to': '100',
+               'keyTimes': '0.0; 0.5; 1.0' },
+    'times': [ [ 2, -100 ] ]
+  });
+
+  // unfrozen to calcMode=discrete two keyTimes
+  testCases.push({
+    'attr' : { 'to': '100',
+               'calcMode': 'discrete',
+               'keyTimes': '0.0; 1.0',
+               'fill': 'remove' },
+    'times': [ [ 0, -100 ],
+               [ 7, -100 ],
+               [ 10, -100 ],
+               [ 12, -100 ]]
+  });
+
+  // frozen to calcMode=discrete two keyTimes
+  testCases.push({
+    'attr' : { 'to': '100',
+               'calcMode': 'discrete',
+               'keyTimes': '0.0; 1.0' },
+    'times': [ [ 0, -100 ],
+               [ 7, -100 ],
+               [ 10, 100 ],
+               [ 12, 100 ] ]
+  });
+
+  // to calcMode=discrete -- bad number of keyTimes (one, expecting two)
+  testCases.push({
+    'attr' : { 'to': '100',
+               'calcMode': 'discrete',
+               'keyTimes': '0' },
+    'times': [ [ 0, -100 ],
+               [ 7, -100 ] ]
+  });
+
+  // values calcMode=discrete
+  testCases.push({
+    'attr' : { 'values': '0; 10; 20; 30',
+               'calcMode': 'discrete',
+               'keyTimes': '0;.2;.4;.6' },
+    'times': [ [ 0, 0 ],
+               [ 1.9, 0 ],
+               [ 2, 10 ],
+               [ 3.9, 10 ],
+               [ 4.0, 20 ],
+               [ 5.9, 20 ],
+               [ 6.0, 30 ],
+               [ 9.9, 30 ],
+               [ 10.0, 30 ] ]
+  });
+
+  // The following two accumulate tests are from SMIL 3.0
+  // (Note that this behaviour differs from that defined for SVG Tiny 1.2 which
+  // specifically excludes the last value: "Note that in the case of discrete
+  // animation, the frozen value that is used is the value of the animation just
+  // before the end of the active duration.")
+  // accumulate=none
+  testCases.push({
+    'attr' : { 'values': '0; 10; 20',
+               'calcMode': 'discrete',
+               'keyTimes': '0;.5;1',
+               'fill': 'freeze',
+               'repeatCount': '2',
+               'accumulate': 'none' },
+    'times': [ [ 0, 0 ],
+               [ 5, 10 ],
+               [ 10, 0 ],
+               [ 15, 10 ],
+               [ 20, 20 ],
+               [ 25, 20 ] ]
+  });
+
+  // accumulate=sum
+  testCases.push({
+    'attr' : { 'values': '0; 10; 20',
+               'calcMode': 'discrete',
+               'keyTimes': '0;.5;1',
+               'fill': 'freeze',
+               'repeatCount': '2',
+               'accumulate': 'sum' },
+    'times': [ [ 0, 0 ],
+               [ 5, 10 ],
+               [ 10, 20 ],
+               [ 15, 30 ],
+               [ 20, 40 ],
+               [ 25, 40 ] ]
+  });
+
+  // If the interpolation mode is paced, the keyTimes attribute is ignored.
+  testCases.push({
+    'attr' : { 'values': '0; 10; 20',
+               'calcMode': 'paced',
+               'keyTimes': '0;.2;1' },
+    'times': [ [ 0, 0 ],
+               [ 2, 4 ],
+               [ 5, 10 ] ]
+  });
+
+  // SMIL 3 has:
+  //   If the simple duration is indefinite and the interpolation mode is
+  //   linear or spline, any keyTimes specification will be ignored.
+  // However, since keyTimes represent "a proportional offset into the simple
+  // duration of the animation element" surely discrete animation too cannot use
+  // keyTimes when the simple duration is indefinite. Hence SVGT 1.2 is surely
+  // more correct when it has:
+  //   If the simple duration is indefinite, any 'keyTimes' specification will
+  //   be ignored.
+  // (linear)
+  testCases.push({
+    'attr' : { 'values': '0; 10; 20',
+               'dur': 'indefinite',
+               'keyTimes': '0;.2;1' },
+    'times': [ [ 0, 0 ],
+               [ 5, 0 ] ]
+  });
+  // (spline)
+  testCases.push({
+    'attr' : { 'values': '0; 10; 20',
+               'dur': 'indefinite',
+               'calcMode': 'spline',
+               'keyTimes': '0;.2;1',
+               'keySplines': '0 0 1 1; 0 0 1 1' },
+    'times': [ [ 0, 0 ],
+               [ 5, 0 ] ]
+  });
+  // (discrete)
+  testCases.push({
+    'attr' : { 'values': '0; 10; 20',
+               'dur': 'indefinite',
+               'calcMode': 'discrete',
+               'keyTimes': '0;.2;1' },
+    'times': [ [ 0, 0 ],
+               [ 5, 0 ] ]
+  });
+
+  for (var i = 0; i < testCases.length; i++) {
+    gSvg.setCurrentTime(0);
+    var test = testCases[i];
+
+    // Create animation elements
+    var anim = createAnim(test.attr);
+
+    // Run samples
+    for (var j = 0; j < test.times.length; j++) {
+      var times = test.times[j];
+      gSvg.setCurrentTime(times[0]);
+      checkSample(anim, times[1], times[0], i);
+    }
+
+    anim.remove();
+  }
+
+  // fallback to discrete for non-additive animation
+  var attr = { 'values': 'butt; round; square',
+               'attributeName': 'stroke-linecap',
+               'calcMode': 'linear',
+               'keyTimes': '0;.2;1',
+               'fill': 'remove' };
+  var anim = createAnim(attr);
+  var samples = [ [ 0, 'butt' ],
+                  [ 1.9, 'butt' ],
+                  [ 2.0, 'round' ],
+                  [ 9.9, 'round' ],
+                  [ 10, 'butt' ] // fill=remove so we'll never set it to square
+                ];
+  for (var i = 0; i < samples.length; i++) {
+    var sample = samples[i];
+    gSvg.setCurrentTime(sample[0]);
+    checkLineCapSample(anim, sample[1], sample[0],
+      "[non-interpolatable fallback]");
+  }
+  anim.remove();
+
+  SimpleTest.finish();
+}
+
+function parseOk(str, extra)
+{
+  var attr = { 'values': '0; 50; 100',
+               'keyTimes': str };
+  if (typeof(extra) == "object") {
+    for (name in extra) {
+      attr[name] = extra[name];
+    }
+  }
+  return {
+    'attr' : attr,
+    'times': [ [ 0, 0 ] ]
+  };
+}
+
+function parseNotOk(str, extra)
+{
+  var result = parseOk(str, extra);
+  result.times = [ [ 0, -100 ] ];
+  return result;
+}
+
+function createAnim(attr)
+{
+  const svgns = "http://www.w3.org/2000/svg";
+  var anim = document.createElementNS(svgns, 'animate');
+  anim.setAttribute('attributeName','cx');
+  anim.setAttribute('dur','10s');
+  anim.setAttribute('begin','0s');
+  anim.setAttribute('fill','freeze');
+  for (name in attr) {
+    anim.setAttribute(name, attr[name]);
+  }
+  return document.getElementById('circle').appendChild(anim);
+}
+
+function checkSample(anim, expectedValue, sampleTime, caseNum)
+{
+  var msg = "Test case " + caseNum +
+    " (keyTimes: '" + anim.getAttribute('keyTimes') + "'" +
+    " calcMode: " + anim.getAttribute('calcMode') + "), " +
+    "t=" + sampleTime +
+    ": Unexpected sample value:";
+  is(anim.targetElement.cx.animVal.value, expectedValue, msg);
+}
+
+function checkLineCapSample(anim, expectedValue, sampleTime, caseDescr)
+{
+  var msg = "Test case " + caseDescr +
+    " (keyTimes: '" + anim.getAttribute('keyTimes') + "'" +
+    " calcMode: " + anim.getAttribute('calcMode') + "), " +
+    "t=" + sampleTime +
+    ": Unexpected sample value:";
+  var actualValue =
+    window.getComputedStyle(anim.targetElement).
+    getPropertyValue('stroke-linecap');
+  is(actualValue, expectedValue, msg);
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilKeyTimesPacedMode.xhtml b/dom/smil/test/test_smilKeyTimesPacedMode.xhtml
new file mode 100644
index 0000000000..f2d6571fa8
--- /dev/null
+++ b/dom/smil/test/test_smilKeyTimesPacedMode.xhtml
@@ -0,0 +1,123 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Tests updated intervals</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=555026">Mozilla Bug 555026</a>
+<p id="display"></p>
+<div id="content">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle r="10" id="circle"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test that we ignore keyTimes attr when calcMode="paced" **/
+
+/* Global Variables */
+const SVGNS = "http://www.w3.org/2000/svg";
+const ANIM_DUR = "2s";
+const HALF_TIME = "1";
+const ATTR_NAME = "cx"
+const KEYTIMES_TO_TEST = [
+  // potentially-valid values (depending on number of values in animation)
+  "0; 0.2; 1",
+  "0; 0.5",
+  "0; 1",
+  // invalid values:
+  "", "abc", "-0.5", "0; 0.5; 1.01", "5"
+];
+const gSvg = document.getElementById("svg");
+const gCircle = document.getElementById("circle");
+
+SimpleTest.waitForExplicitFinish();
+
+
+// MAIN FUNCTIONS
+function main() {
+  ok(gSvg.animationsPaused(), "should be paused by <svg> load handler");
+  is(gSvg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  testByAnimation();
+  testToAnimation();
+  testValuesAnimation();
+  SimpleTest.finish();
+}
+
+function testByAnimation() {
+  for (var i = 0; i < KEYTIMES_TO_TEST.length; i++) {
+    setupTest();
+    var anim = createAnim();
+    anim.setAttribute("by", "200");
+    var curKeyTimes = KEYTIMES_TO_TEST[i];
+    anim.setAttribute("keyTimes", curKeyTimes);
+
+    gSvg.setCurrentTime(HALF_TIME);
+    is(gCircle.cx.animVal.value, 100,
+       "Checking animVal with 'by' and keyTimes='" + curKeyTimes + "'");
+
+    anim.remove(); // clean up
+  }
+}
+
+function testToAnimation() {
+  for (var i = 0; i < KEYTIMES_TO_TEST.length; i++) {
+    setupTest();
+    var anim = createAnim();
+    anim.setAttribute("to", "200");
+    var curKeyTimes = KEYTIMES_TO_TEST[i];
+    anim.setAttribute("keyTimes", curKeyTimes);
+
+    gSvg.setCurrentTime(HALF_TIME);
+    is(gCircle.cx.animVal.value, 100,
+       "Checking animVal with 'to' and keyTimes='" + curKeyTimes + "'");
+
+    anim.remove(); // clean up
+  }
+}
+
+function testValuesAnimation() {
+  for (var i = 0; i < KEYTIMES_TO_TEST.length; i++) {
+    setupTest();
+    var anim = createAnim();
+    anim.setAttribute("values", "100; 110; 200");
+    var curKeyTimes = KEYTIMES_TO_TEST[i];
+    anim.setAttribute("keyTimes", curKeyTimes);
+
+    gSvg.setCurrentTime(HALF_TIME);
+    is(gCircle.cx.animVal.value, 150,
+       "Checking animVal with 'values' and keyTimes='" + curKeyTimes + "'");
+
+    anim.remove(); // clean up
+  }
+}
+
+// HELPER FUNCTIONS
+// Common setup code for each test function: seek to 0, and make sure
+// the previous test cleaned up its animations.
+function setupTest() {
+  gSvg.setCurrentTime(0);
+  if (gCircle.firstChild) {
+    ok(false, "Previous test didn't clean up after itself.");
+  }
+}
+
+function createAnim() {
+  var anim = document.createElementNS(SVGNS,"animate");
+  anim.setAttribute("attributeName", ATTR_NAME);
+  anim.setAttribute("dur", ANIM_DUR);
+  anim.setAttribute("begin", "0s");
+  anim.setAttribute("calcMode", "paced");
+  return gCircle.appendChild(anim);
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilMappedAttrFromBy.xhtml b/dom/smil/test/test_smilMappedAttrFromBy.xhtml
new file mode 100644
index 0000000000..5b70b5b83f
--- /dev/null
+++ b/dom/smil/test/test_smilMappedAttrFromBy.xhtml
@@ -0,0 +1,51 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for Animation Behavior on CSS Properties</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <script type="text/javascript" src="db_smilMappedAttrList.js"></script>
+  <script type="text/javascript" src="db_smilCSSPropertyList.js"></script>
+  <script type="text/javascript" src="db_smilCSSFromBy.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg xmlns="http://www.w3.org/2000/svg"
+     width="200px" height="200px" font-size="50px" style="color: rgb(50,50,50)"
+     onload="this.pauseAnimations()">
+  <rect x="20" y="20" width="200" height="200"/>
+  <!-- NOTE: hard-wiring 'line-height' so that computed value of 'font' is
+       more predictable. (otherwise, line-height varies depending on platform)
+    -->
+  <text x="20" y="20" style="line-height: 10px !important">testing 123</text>
+  <line/>
+  <marker/>
+  <filter><feDiffuseLighting/></filter>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+SimpleTest.waitForExplicitFinish();
+
+function main()
+{
+  // Start out with document paused
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var testBundles = convertCSSBundlesToMappedAttr(gFromByBundles);
+  testBundleList(testBundles, new SMILTimingData(1.0, 1.0));
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilMappedAttrFromTo.xhtml b/dom/smil/test/test_smilMappedAttrFromTo.xhtml
new file mode 100644
index 0000000000..57ef83800e
--- /dev/null
+++ b/dom/smil/test/test_smilMappedAttrFromTo.xhtml
@@ -0,0 +1,79 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for Animation Behavior on CSS Properties</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <script type="text/javascript" src="db_smilMappedAttrList.js"></script>
+  <script type="text/javascript" src="db_smilCSSPropertyList.js"></script>
+  <script type="text/javascript" src="db_smilCSSFromTo.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg xmlns="http://www.w3.org/2000/svg"
+     width="200px" height="200px" font-size="50px" style="color: rgb(50,50,50)"
+     onload="this.pauseAnimations()">
+  <rect x="20" y="20" width="200" height="200"/>
+  <!-- NOTE: hard-wiring 'line-height' so that computed value of 'font' is
+       more predictable. (otherwise, line-height varies depending on platform)
+    -->
+  <text x="20" y="20">testing 123</text>
+  <line/>
+  <image/>
+  <marker/>
+  <clipPath><circle/></clipPath>
+  <filter><feFlood/></filter>
+  <filter><feDiffuseLighting/></filter>
+  <linearGradient><stop/></linearGradient>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+SimpleTest.waitForExplicitFinish();
+
+function checkForUntestedAttributes(bundleList)
+{
+  // Create the set of all the attributes we know about
+  var attributeSet = {};
+  for (attributeLabel in gMappedAttrList) {
+    // insert attribute
+    attributeSet[gMappedAttrList[attributeLabel].attrName] = null;
+  }
+  // Remove tested properties from the set
+  for (var bundleIdx in bundleList) {
+    var bundle = bundleList[bundleIdx];
+    delete attributeSet[bundle.animatedAttribute.attrName];
+  }
+  // Warn about remaining (untested) properties
+  for (var untestedProp in attributeSet) {
+    ok(false, "No tests for attribute '" + untestedProp + "'");
+  }
+}
+
+function main()
+{
+  // Start out with document paused
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var testBundles = convertCSSBundlesToMappedAttr(gFromToBundles);
+
+  // FIRST: Warn about any attributes that are missing tests
+  checkForUntestedAttributes(testBundles);
+
+  // Run the actual tests
+  testBundleList(testBundles, new SMILTimingData(1.0, 1.0));
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilMappedAttrPaced.xhtml b/dom/smil/test/test_smilMappedAttrPaced.xhtml
new file mode 100644
index 0000000000..81adea6390
--- /dev/null
+++ b/dom/smil/test/test_smilMappedAttrPaced.xhtml
@@ -0,0 +1,46 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for Animation Behavior on CSS Properties</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <script type="text/javascript" src="db_smilMappedAttrList.js"></script>
+  <script type="text/javascript" src="db_smilCSSPropertyList.js"></script>
+  <script type="text/javascript" src="db_smilCSSPaced.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg xmlns="http://www.w3.org/2000/svg"
+     width="200px" height="200px" font-size="50px" style="color: rgb(50,50,50)"
+     onload="this.pauseAnimations()">
+  <rect x="20" y="20" width="200" height="200"/>
+  <text x="20" y="20">testing 123</text>
+  <marker/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+
+SimpleTest.waitForExplicitFinish();
+
+function main()
+{
+  // Start out with document paused
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var testBundles = convertCSSBundlesToMappedAttr(gPacedBundles);
+  testBundleList(testBundles, new SMILTimingData(1.0, 6.0));
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilMinTiming.html b/dom/smil/test/test_smilMinTiming.html
new file mode 100644
index 0000000000..f0bdd42502
--- /dev/null
+++ b/dom/smil/test/test_smilMinTiming.html
@@ -0,0 +1,93 @@
+<!doctype html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=948245
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 948245</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=948245">Mozilla Bug 948245</a>
+<p id="display"></p>
+<div id="content">
+<svg id="svg" onload="this.pauseAnimations()">
+  <rect fill="red" id="rect" x="0">
+    <animate attributeName="x" to="100" id="animation" dur="100s" min="200s"/>
+  </rect>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+  // The 'min' attribute introduces a kind of additional state into the SMIL
+  // model. If the 'min' attribute extends the active duration, the additional
+  // time between the amount of time the animation normally runs for (called the
+  // 'repeat duration') and the extended active duration is filled using the
+  // fill mode.
+  //
+  // Below we refer to this period of time between the end of the repeat
+  // duration and the end of the active duration as the 'extended period'.
+  //
+  // This test verifies that as we jump in and out of these states we produce
+  // the correct values.
+  //
+  // The test animation above produces an active interval that is longer than
+  // the 'repeating duration' of the animation.
+  var rect      = $('rect'),
+      animation = $('animation');
+
+  // Animation doesn't start until onload
+  SimpleTest.waitForExplicitFinish();
+  window.addEventListener("load", runTests);
+
+  function runTests() {
+    ok($('svg').animationsPaused(), "should be paused by <svg> load handler");
+
+    // In the extended period (t=150s) we should not be animating or filling
+    // since the default fill mode is "none".
+    animation.ownerSVGElement.setCurrentTime(150);
+    is(rect.x.animVal.value, 0,
+       "Shouldn't fill in extended period with fill='none'");
+
+    // If we set the fill mode we should start filling.
+    animation.setAttribute("fill", "freeze");
+    is(rect.x.animVal.value, 100,
+       "Should fill in extended period with fill='freeze'");
+
+    // If we unset the fill attribute we should stop filling.
+    animation.removeAttribute("fill");
+    is(rect.x.animVal.value, 0, "Shouldn't fill after unsetting fill");
+
+    // If we jump back into the repeated interval (at t=50s) we should be
+    // animating.
+    animation.ownerSVGElement.setCurrentTime(50);
+    is(rect.x.animVal.value, 50, "Should be active in repeating interval");
+
+    // If we jump to the boundary at the start of the extended period we should
+    // not be filling (since we removed the fill attribute above).
+    animation.ownerSVGElement.setCurrentTime(100);
+    is(rect.x.animVal.value, 0,
+       "Shouldn't fill after seeking to boundary of extended period");
+
+    // If we apply a fill mode at this boundary point we should do regular fill
+    // behavior of using the last value in the interpolation range.
+    animation.setAttribute("fill", "freeze");
+    is(rect.x.animVal.value, 100,
+       "Should fill at boundary to extended period");
+
+    // Check that if we seek past the interval we fill with the value at the end
+    // of the _repeat_duration_ not the value at the end of the
+    // _active_duration_.
+    animation.setAttribute("repeatCount", "1.5");
+    animation.ownerSVGElement.setCurrentTime(225);
+    is(rect.x.animVal.value, 50,
+       "Should fill with the end of the repeat duration value");
+
+    SimpleTest.finish();
+  }
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilRepeatDuration.html b/dom/smil/test/test_smilRepeatDuration.html
new file mode 100644
index 0000000000..b746bb45d4
--- /dev/null
+++ b/dom/smil/test/test_smilRepeatDuration.html
@@ -0,0 +1,139 @@
+<!doctype html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=948245
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for repeat duration calculation (Bug 948245)</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank"
+href="https://bugzilla.mozilla.org/show_bug.cgi?id=948245">Mozilla Bug 948245</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" onload="this.pauseAnimations()">
+  <rect>
+    <animate id="a"/>
+    <animate id="b" begin="a.end"/>
+  </rect>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+  // Tests the calculation of the repeat duration which is one of the steps
+  // towards determining the active duration.
+  //
+  // The repeat duration is determined by the following three attributes:
+  //
+  // dur:         may be definite (e.g. '2s') or 'indefinite' (the default)
+  // repeatCount: may be definite (e.g. '2.5'), 'indefinite', or not set
+  // repeatDur:   may be definite (e.g. '5s'), 'indefinite', or not set
+  //
+  // That leaves 18 combinations to test.
+  var testCases =
+    [
+      // 1. repeatDur: definite, repeatCount: definite, dur: definite
+      // (Two test cases here to ensure we get the minimum)
+      { repeatDur: 15, repeatCount: 2, dur: 10, result: 15 },
+      { repeatDur: 25, repeatCount: 2, dur: 10, result: 20 },
+      // 2. repeatDur: indefinite, repeatCount: definite, dur: definite
+      { repeatDur: 'indefinite', repeatCount: 2, dur: 10, result: 20 },
+      // 3. repeatDur: not set, repeatCount: definite, dur: definite
+      { repeatCount: 2, dur: 10, result: 20 },
+      // 4. repeatDur: definite, repeatCount: indefinite, dur: definite
+      { repeatDur: 15, repeatCount: 'indefinite', dur: 10, result: 15 },
+      // 5. repeatDur: indefinite, repeatCount: indefinite, dur: definite
+      { repeatDur: 'indefinite', repeatCount: 'indefinite', dur: 10,
+        result: 'indefinite' },
+      // 6. repeatDur: not set, repeatCount: indefinite, dur: definite
+      { repeatCount: 'indefinite', dur: 10, result: 'indefinite' },
+      // 7. repeatDur: definite, repeatCount: not set, dur: definite
+      { repeatDur: 15, dur: 10, result: 15 },
+      // 8. repeatDur: indefinite, repeatCount: not set, dur: definite
+      { repeatDur: 'indefinite', dur: 10, result: 'indefinite' },
+      // 9. repeatDur: not set, repeatCount: not set, dur: definite
+      { dur: 10, result: 10 },
+      // 10. repeatDur: definite, repeatCount: definite, dur: indefinite
+      { repeatDur: 15, repeatCount: 2, dur: 'indefinite', result: 15 },
+      // 11. repeatDur: indefinite, repeatCount: definite, dur: indefinite
+      { repeatDur: 'indefinite', repeatCount: 2, dur: 'indefinite',
+        result: 'indefinite' },
+      // 12. repeatDur: not set, repeatCount: definite, dur: indefinite
+      { repeatCount: 2, dur: 'indefinite', result: 'indefinite' },
+      // 13. repeatDur: definite, repeatCount: indefinite, dur: indefinite
+      { repeatDur: 15, repeatCount: 'indefinite', dur: 'indefinite',
+        result: 15 },
+      // 14. repeatDur: indefinite, repeatCount: indefinite, dur: indefinite
+      { repeatDur: 'indefinite', repeatCount: 'indefinite', dur: 'indefinite',
+        result: 'indefinite' },
+      // 15. repeatDur: not set, repeatCount: indefinite, dur: indefinite
+      { repeatCount: 'indefinite', dur: 'indefinite', result: 'indefinite' },
+      // 16. repeatDur: definite, repeatCount: not set, dur: indefinite
+      { repeatDur: 15, dur: 'indefinite', result: 15 },
+      // 17. repeatDur: indefinite, repeatCount: not set, dur: indefinite
+      { repeatDur: 'indefinite', dur: 'indefinite', result: 'indefinite' },
+      // 18. repeatDur: not set, repeatCount: not set, dur: indefinite
+      { dur: 'indefinite', result: 'indefinite' }
+    ];
+
+  // We can test the repeat duration by setting these attributes on animation
+  // 'a' and checking the start time of 'b' which is defined to start when 'a'
+  // finishes.
+  //
+  // Since 'a' has no end/min/max attributes the end of its active interval
+  // should coincide with the end of its repeat duration.
+  //
+  // Sometimes the repeat duration is defined to be 'indefinite'. In this case
+  // calling getStartTime on b will throw an exception so we need to catch that
+  // exception and translate it to 'indefinite' as follows:
+  function getRepeatDuration() {
+    try {
+      return $('b').getStartTime();
+    } catch(e) {
+      if (e.name == "InvalidStateError" &&
+          e.code == DOMException.INVALID_STATE_ERR) {
+        return 'indefinite';
+      } else {
+        ok(false, "Unexpected exception: " + e);
+        return null;
+      }
+    }
+  }
+
+  // Animation doesn't start until onload
+  SimpleTest.waitForExplicitFinish();
+  window.addEventListener("load", runTests);
+
+  // Run through each of the test cases
+  function runTests() {
+    ok($('svg').animationsPaused(), "should be paused by <svg> load handler");
+
+    testCases.forEach(function(test) {
+      var a = $('a');
+
+      // Set the attributes
+      var msgPieces = [];
+      [ 'repeatDur', 'repeatCount', 'dur' ].forEach(function(attr) {
+        if (typeof test[attr] != "undefined") {
+          a.setAttribute(attr, test[attr].toString());
+          msgPieces.push(attr + ': ' + test[attr].toString());
+        } else {
+          a.removeAttribute(attr);
+          msgPieces.push(attr + ': <not set>');
+        }
+      });
+      var msg = msgPieces.join(', ');
+
+      // Check the result
+      is(getRepeatDuration(), test.result, msg);
+    });
+
+    SimpleTest.finish();
+  }
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilRepeatTiming.xhtml b/dom/smil/test/test_smilRepeatTiming.xhtml
new file mode 100644
index 0000000000..ace63d37b0
--- /dev/null
+++ b/dom/smil/test/test_smilRepeatTiming.xhtml
@@ -0,0 +1,96 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=485157
+-->
+<head>
+  <title>Test repeat timing</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank"
+  href="https://bugzilla.mozilla.org/show_bug.cgi?id=485157">Mozilla Bug
+  485157</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="100px" height="100px">
+  <rect width="100" height="100" fill="green">
+    <set attributeName="width" to="100" dur="20s" repeatCount="5" begin="0s"
+      id="a" onrepeat="startWaiting(evt)"/>
+    <set attributeName="fill" attributeType="CSS" to="green"
+      begin="a.repeat(1)" onbegin="expectedBegin()" dur="20s"/>
+    <set attributeName="x" to="100"
+      begin="a.repeat(2)" onbegin="unexpectedBegin(this)" dur="20s"/>
+    <set attributeName="y" to="100"
+      begin="a.repeat(0)" onbegin="unexpectedBegin(this)" dur="20s"/>
+    <set attributeName="width" to="100"
+      begin="a.repeat(-1)" onbegin="unexpectedBegin(this)" dur="20s"/>
+    <set attributeName="height" to="100"
+      begin="a.repeat(a)" onbegin="unexpectedBegin(this)" dur="20s"/>
+  </rect>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test SMIL repeat timing **/
+
+/* Global Variables */
+const gTimeoutDur = 5000; // Time until we give up waiting for events in ms
+var gSvg  = document.getElementById('svg');
+var gRect = document.getElementById('circle');
+var gTimeoutID;
+var gGotBegin = false;
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestFlakyTimeout("untriaged");
+
+function testBegin()
+{
+  gSvg.setCurrentTime(19.999);
+}
+
+function startWaiting(evt)
+{
+  is(evt.detail, 1, "Unexpected repeat event received: test broken");
+  if (gGotBegin)
+    return;
+
+  gTimeoutID = setTimeout(timeoutFail, gTimeoutDur);
+}
+
+function timeoutFail()
+{
+  ok(false, "Timed out waiting for begin event");
+  finish();
+}
+
+function expectedBegin()
+{
+  is(gGotBegin, false,
+     "Got begin event more than once for non-repeating animation");
+  gGotBegin = true;
+  clearTimeout(gTimeoutID);
+  // Wait a moment before finishing in case there are erroneous events waiting
+  // to be processed.
+  setTimeout(finish, 10);
+}
+
+function unexpectedBegin(elem)
+{
+  ok(false, "Got unexpected begin from animation with spec: " +
+            elem.getAttribute('begin'));
+}
+
+function finish()
+{
+  gSvg.pauseAnimations();
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", testBegin);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilReset.xhtml b/dom/smil/test/test_smilReset.xhtml
new file mode 100644
index 0000000000..a53f73c112
--- /dev/null
+++ b/dom/smil/test/test_smilReset.xhtml
@@ -0,0 +1,82 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Tests for SMIL Reset Behavior </title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animate attributeName="cx" from="20" to="100" begin="2s" dur="4s"
+             id="anim1" attributeType="XML"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Tests for SMIL Reset Behavior  **/
+
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  var svg = document.getElementById("svg");
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var anim = document.getElementById("anim1");
+  is(anim.getStartTime(), 2, "Unexpected initial start time");
+
+  svg.setCurrentTime(1);
+  anim.beginElementAt(2);
+
+  // We now have two instance times: 2, 3
+
+  // Restart (and reset) animation at t=1
+  anim.beginElement();
+
+  // Instance times should now be 1, 2 (3 should have be reset)
+  is(anim.getStartTime(), 1,
+    "Unexpected start time after restart. Perhaps the added instance time "
+    + "was cleared");
+  svg.setCurrentTime(4);
+  // Instance times will now be 2 (1 will have be reset when we restarted)
+  is(anim.getStartTime(), 2, "Unexpected start time after seek");
+
+  // Create a two new instance times at t=4, 5
+  anim.beginElement();
+  anim.beginElementAt(1);
+  is(anim.getStartTime(), 4, "Unexpected start time after beginElement");
+
+  // Here is a white box test to make sure we don't discard instance times
+  // created by DOM calls when setting/unsetting the 'begin' spec
+  anim.removeAttribute('begin');
+  is(anim.getStartTime(), 4, "Unexpected start time after clearing begin spec");
+  svg.setCurrentTime(6);
+  is(anim.getStartTime(), 5,
+    "Second DOM instance time cleared when begin spec was removed");
+
+  // And likewise, when we set it again
+  anim.beginElementAt(1); // Instance times now t=5s, 7s
+  anim.setAttribute('begin', '1s'); // + t=1s
+  is(anim.getStartTime(), 5, "Unexpected start time after setting begin spec");
+  svg.setCurrentTime(8);
+  is(anim.getStartTime(), 7,
+    "Second DOM instance time cleared when begin spec was added");
+
+  // But check we do update state appropriately
+  anim.setAttribute('begin', '8s');
+  is(anim.getStartTime(), 8, "Interval not updated with updated begin spec");
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilRestart.xhtml b/dom/smil/test/test_smilRestart.xhtml
new file mode 100644
index 0000000000..3e03dfdbcc
--- /dev/null
+++ b/dom/smil/test/test_smilRestart.xhtml
@@ -0,0 +1,102 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL Restart Behavior </title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <!-- These 3 circles only differ in their animation's "restart" value -->
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animate attributeName="cx" from="20" to="100" begin="1s" dur="4s"
+             restart="always" id="always" attributeType="XML"/>
+  </circle>
+  <circle cx="20" cy="60" r="15" fill="blue">
+    <animate attributeName="cx" from="20" to="100" begin="1s" dur="4s"
+             restart="whenNotActive" id="whenNotActive" attributeType="XML"/>
+  </circle>
+  <circle cx="20" cy="100" r="15" fill="blue">
+    <animate attributeName="cx" from="20" to="100" begin="1s" dur="4s"
+             restart="never" id="never" attributeType="XML"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL Restart Behavior  **/
+
+/* Global Variables */
+var svg = document.getElementById("svg");
+var always = document.getElementById("always");
+var whenNotActive = document.getElementById("whenNotActive");
+var never = document.getElementById("never");
+
+SimpleTest.waitForExplicitFinish();
+
+function tryRestart(elem, state, expected) {
+  var restartTime = svg.getCurrentTime();
+  elem.beginElement();
+  var restart = false;
+  try {
+    restart = (elem.getStartTime() === restartTime);
+  } catch (e) {
+    if (e.name != "InvalidStateError" ||
+        e.code != DOMException.INVALID_STATE_ERR)
+      throw e;
+    restart = false;
+  }
+  if (expected) {
+    var msg = elem.id + " can't restart in " + state + " state";
+    ok(restart, msg);
+  } else {
+    var msg = elem.id + " can restart in " + state + " state";
+    ok(!restart, msg);
+  }
+}
+
+function main() {
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  // At first everything should be starting at 1s
+  is(always.getStartTime(), 1);
+  is(whenNotActive.getStartTime(), 1);
+  is(never.getStartTime(), 1);
+
+  // Now try to restart everything early, should be allowed by all
+  tryRestart(always, "waiting", true);
+  tryRestart(whenNotActive, "waiting", true);
+  tryRestart(never, "waiting", true);
+
+  // Now skip to half-way
+  var newTime = always.getStartTime() + 0.5 * always.getSimpleDuration();
+  svg.setCurrentTime(newTime);
+
+  // Only 'always' should be able to be restarted
+  tryRestart(always, "active", true);
+  tryRestart(whenNotActive, "active", false);
+  tryRestart(never, "active", false);
+
+  // Now skip to the end 
+  newTime = always.getStartTime() + always.getSimpleDuration() + 1;
+  svg.setCurrentTime(newTime);
+
+  // All animations have finished, so 'always' and 'whenNotActive' should be
+  // able to be restarted
+  tryRestart(always, "postactive", true);
+  tryRestart(whenNotActive, "postactive", true);
+  tryRestart(never, "postactive", false);
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilSetCurrentTime.xhtml b/dom/smil/test/test_smilSetCurrentTime.xhtml
new file mode 100644
index 0000000000..91ded84c8c
--- /dev/null
+++ b/dom/smil/test/test_smilSetCurrentTime.xhtml
@@ -0,0 +1,76 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for setCurrentTime Behavior </title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg"
+     onload="this.pauseAnimations()" />
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for basic setCurrentTime / getCurrentTime Behavior  **/
+
+/* Global Variables & Constants */
+const PRECISION_LEVEL = 0.0000001; // Allow small level of floating-point error
+const gTimes = [0, 1.5, 0.2, 0.99, -400.5, 10000000, -1];
+const gWaitTime = 20;
+var gSvg = document.getElementById("svg");
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestFlakyTimeout("untriaged");
+
+function main() {
+  ok(gSvg.animationsPaused(), "should be paused by <svg> load handler");
+  is(gSvg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  // Test that seeking takes effect immediately
+  for (var i = 0; i < gTimes.length; i++) {
+    gSvg.setCurrentTime(gTimes[i]);
+    // We adopt the SVGT1.2 behavior of clamping negative times to 0
+    assertFloatsEqual(gSvg.getCurrentTime(), Math.max(gTimes[i], 0.0));
+  }
+
+  // Test that seeking isn't messed up by timeouts
+  // (using tail recursion to set up the chain of timeout function calls)
+  var func = function() {
+    checkTimesAfterIndex(0);
+  }
+  setTimeout(func, gWaitTime);
+}
+
+/* This method seeks to the time at gTimes[index],
+ * and then sets up a timeout to...
+ *   - verify that the seek worked
+ *   - make a recursive call for the next index.
+ */
+function checkTimesAfterIndex(index) {
+  if (index == gTimes.length) {
+    // base case -- we're done!
+    SimpleTest.finish();
+    return;
+  }
+
+  gSvg.setCurrentTime(gTimes[index]);
+  var func = function() {
+    assertFloatsEqual(gSvg.getCurrentTime(), Math.max(gTimes[index], 0.0));
+    checkTimesAfterIndex(index + 1);
+  }
+  setTimeout(func, gWaitTime);
+}
+
+function assertFloatsEqual(aVal, aExpected) {
+  ok(Math.abs(aVal - aExpected) <= PRECISION_LEVEL,
+     "getCurrentTime returned " + aVal + " after seeking to " + aExpected)
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilSync.xhtml b/dom/smil/test/test_smilSync.xhtml
new file mode 100644
index 0000000000..36b2a91198
--- /dev/null
+++ b/dom/smil/test/test_smilSync.xhtml
@@ -0,0 +1,255 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL sync behaviour </title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px">
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animate attributeName="cx" attributeType="XML" from="20" to="100"
+      begin="indefinite" dur="4s" restart="always" id="anim1"/>
+  </circle>
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animate attributeName="cx" attributeType="XML" from="0" to="50"
+      begin="0" dur="1s" additive="sum" fill="freeze" id="anim2"/>
+  </circle>
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animate attributeName="cx" attributeType="XML" from="0" to="50"
+      begin="0" dur="10s" additive="sum" fill="freeze" id="anim3"/>
+  </circle>
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animate attributeName="cx" attributeType="XML" from="0" to="50"
+      begin="0" dur="10s" additive="sum" fill="freeze" id="anim4"/>
+  </circle>
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animate attributeName="cx" attributeType="XML" from="0" to="50"
+      begin="0" dur="40s" additive="sum" fill="freeze" id="anim5"/>
+  </circle>
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animate attributeName="cx" attributeType="XML" from="20" to="100"
+      begin="100s" dur="4s" restart="always" id="anim6"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL sync behavior  **/
+
+/* Global Variables */
+var svg = document.getElementById("svg");
+
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  testBeginAt(document.getElementById("anim1"));
+  testChangeBaseVal(document.getElementById("anim2"));
+  testChangeWhilePaused(document.getElementById("anim3"));
+  testChangeAnimAttribute(document.getElementById("anim4"));
+  testChangeTimingAttribute(document.getElementById("anim5"));
+  testSetCurrentTime(document.getElementById("anim6"));
+  SimpleTest.finish();
+}
+
+function testBeginAt(anim) {
+  // This (hugely important) test checks that a call to beginElement updates to
+  // the new interval
+
+  // Check some pre-conditions
+  is(anim.getAttribute("restart"), "always");
+  ok(anim.getSimpleDuration() >= 4);
+
+  // First start the animation
+  svg.setCurrentTime(2);
+  anim.beginElement();
+
+  // Then restart it--twice
+  svg.setCurrentTime(4);
+  anim.beginElement();
+  anim.beginElementAt(-1);
+
+  // The first restart should win if the state machine has been successfully
+  // updated. If we get '3' back instead we haven't updated properly.
+  is(anim.getStartTime(), 4);
+}
+
+function testChangeBaseVal(anim) {
+  // Check that a change to the base value is updated even after animation is
+  // frozen
+
+  // preconditions -- element should have ended
+  try {
+    anim.getStartTime();
+    ok(false, "Element has not ended yet.");
+  } catch (e) { }
+
+  // check frozen value is applied
+  var target = anim.targetElement;
+  is(target.cx.animVal.value, 70);
+  is(target.cx.baseVal.value, 20);
+
+  // change base val and re-check
+  target.cx.baseVal.value = 30;
+  is(target.cx.animVal.value, 80);
+  is(target.cx.baseVal.value, 30);
+}
+
+function testChangeWhilePaused(anim) {
+  // Check that a change to the base value is updated even when the animation is
+  // paused
+
+  svg.pauseAnimations();
+  svg.setCurrentTime(anim.getSimpleDuration() / 2);
+
+  // check paused value is applied
+  var target = anim.targetElement;
+  is(target.cx.animVal.value, 45);
+  is(target.cx.baseVal.value, 20);
+
+  // change base val and re-check
+  target.cx.baseVal.value = 30;
+  is(target.cx.animVal.value, 55);
+  is(target.cx.baseVal.value, 30);
+}
+
+function testChangeAnimAttribute(anim) {
+  // Check that a change to an animation attribute causes an update even when
+  // the animation is frozen and paused
+
+  // Make sure animation is paused and frozen
+  svg.pauseAnimations();
+  svg.setCurrentTime(anim.getStartTime() + anim.getSimpleDuration() + 1);
+
+  // Check frozen value is applied
+  var target = anim.targetElement;
+  is(target.cx.animVal.value, 70);
+  is(target.cx.baseVal.value, 20);
+
+  // Make the animation no longer additive
+  anim.removeAttribute("additive");
+  is(target.cx.animVal.value, 50);
+  is(target.cx.baseVal.value, 20);
+}
+
+function testChangeTimingAttribute(anim) {
+  // Check that a change to a timing attribute causes an update even when
+  // the animation is paused
+
+  svg.pauseAnimations();
+  svg.setCurrentTime(anim.getSimpleDuration() / 2);
+
+  // Check part-way value is applied
+  var target = anim.targetElement;
+  is(target.cx.animVal.value, 45);
+  is(target.cx.baseVal.value, 20);
+
+  // Make the animation no longer additive
+  anim.setAttribute("dur", String(anim.getSimpleDuration() / 2) + "s");
+  is(target.cx.animVal.value, 70);
+  is(target.cx.baseVal.value, 20);
+
+  // Remove fill
+  anim.removeAttribute("fill");
+  is(target.cx.animVal.value, 20);
+  is(target.cx.baseVal.value, 20);
+}
+
+function testSetCurrentTime(anim) {
+  // This test checks that a call to setCurrentTime flushes restarts
+  //
+  // Actually, this same scenario arises in test_smilRestart.xhtml but we
+  // isolate this particular situation here for easier diagnosis if this ever
+  // fails.
+  //
+  // At first we have:
+  //                       currentTime   begin="100s"
+  //                            v            v
+  // Doc time: 0---\/\/\/-------99----------100-------
+  //
+  svg.setCurrentTime(99);
+  is(anim.getStartTime(), 100);
+
+  // Then we restart giving us:
+  //
+  //                       beginElement begin="100s"
+  //                            v            v
+  // Doc time: 0---\/\/\/-------99----------100-------
+  //
+  // So our current interval is
+  //
+  //                            begin="100s"
+  //                                v
+  //                            +---------------|
+  // Doc time: 0---\/\/\/-------99-100-101-102-103-----
+  //
+  anim.beginElement();
+  is(anim.getStartTime(), svg.getCurrentTime());
+
+  // Then we skip to half-way, i.e.
+  //
+  //                                currentTime
+  //                                    v
+  //                            begin="100s"
+  //                                v
+  //                            +---------------|
+  // Doc time: 0---\/\/\/-------99-100-101-102-103-----
+  //
+  // At this point we should flush our restarts and early end the first interval
+  // and start the second interval, giving us
+  //
+  // So our timegraph looks like:
+  //
+  //                                currentTime
+  //                                    v
+  //                                +---------------|
+  //                            +---|
+  // Doc time: 0---\/\/\/-------99-100-101-102-103-104-
+  //
+  var newTime = anim.getStartTime() + 0.5 * anim.getSimpleDuration();
+  svg.setCurrentTime(newTime);
+
+  // Finally we call beginElement again giving us
+  //
+  //                                currentTime
+  //                                    v
+  //                                    +---------------|
+  //                                +---|
+  //                            +---|
+  // Doc time: 0---\/\/\/-------99-100-101-102-103-104-105-
+  //
+  // If, however, setCurrentTime failed to flush restarts out starting point
+  // we do come to update the timegraph would be:
+  //
+  //                              beginElementAt
+  //                                    v
+  //                            begin="100s"
+  //                                v
+  //                            +---------------|
+  // Doc time: 0---\/\/\/-------99-100-101-102-103-----
+  //
+  // And as soon as we encountered the begin="100s" spec we'd do a restart
+  // according to the SMIL algorithms and a restart involves a reset which
+  // clears the instance times created by DOM calls and so we'd end up with
+  // just:
+  //
+  //                                currentTime
+  //                                    v
+  //                                +---------------|
+  //                            +---|
+  // Doc time: 0---\/\/\/-------99-100-101-102-103-104-
+  //
+  // Which is probably not what the author intended.
+  //
+  anim.beginElement();
+  is(anim.getStartTime(), svg.getCurrentTime());
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilSyncTransform.xhtml b/dom/smil/test/test_smilSyncTransform.xhtml
new file mode 100644
index 0000000000..79c5cbf0b9
--- /dev/null
+++ b/dom/smil/test/test_smilSyncTransform.xhtml
@@ -0,0 +1,66 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL sync behaviour for transform types</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px">
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animateTransform attributeName="transform" type="rotate"
+      from="90" to="180" begin="0s" dur="2s" fill="freeze"
+      additive="sum" id="anim1"/>
+  </circle>
+  <circle cx="20" cy="20" r="15" fill="blue">
+    <animateTransform attributeName="transform" type="scale"
+      from="1" to="2" begin="2s" dur="2s" id="anim2"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL sync behavior for transform types **/
+
+/* Global Variables */
+var svg = document.getElementById("svg");
+
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  testChangeBaseVal(document.getElementById("anim1"));
+  SimpleTest.finish();
+}
+
+function testChangeBaseVal(anim) {
+  // Check that a change to the base value is updated even after animation is
+  // frozen
+
+  var target = anim.targetElement;
+
+  var baseList = target.transform.baseVal;
+  var animList = target.transform.animVal;
+
+  // make sure element has ended
+  svg.setCurrentTime(anim.getSimpleDuration());
+
+  // check frozen value is applied
+  is(baseList.numberOfItems, 0);
+  is(animList.numberOfItems, 1);
+
+  // change base val and re-check
+  var newTransform = svg.createSVGTransform();
+  newTransform.setScale(1,2);
+  baseList.appendItem(newTransform);
+  is(baseList.numberOfItems, 1);
+  is(animList.numberOfItems, 2);
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilSyncbaseTarget.xhtml b/dom/smil/test/test_smilSyncbaseTarget.xhtml
new file mode 100644
index 0000000000..496cb6751e
--- /dev/null
+++ b/dom/smil/test/test_smilSyncbaseTarget.xhtml
@@ -0,0 +1,180 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for syncbase targetting</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="-20" cy="20" r="15" fill="blue" id="circle">
+    <set attributeName="cx" to="0" begin="2s" dur="1s" id="a"/>
+    <set attributeName="cx" to="0" begin="2s" dur="1s" xml:id="b"/>
+    <set attributeName="cx" to="0" begin="2s" dur="1s" id="あ"/>
+    <set attributeName="cx" to="0" begin="2s" dur="1s" id="a.b"/>
+    <set attributeName="cx" to="0" begin="2s" dur="1s" id="a-b"/>
+    <set attributeName="cx" to="0" begin="2s" dur="1s" id="a:b"/>
+    <set attributeName="cx" to="0" begin="2s" dur="1s" id="-a"/>
+    <set attributeName="cx" to="0" begin="2s" dur="1s" id="0"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for syncbase targetting behavior  **/
+
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  var svg = getElement("svg");
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  testSpecs();
+  testChangeId();
+  testRemoveTimebase();
+
+  SimpleTest.finish();
+}
+
+function testSpecs() {
+  var anim = createAnim();
+
+  // Sanity check--initial state
+  ok(noStart(anim), "Unexpected initial value for indefinite start time.");
+
+  var specs = [ [ 'a.begin', 2 ],
+                [ 'b.begin', 'todo' ], // xml:id support, bug 275196
+                [ 'あ.begin', 2 ],   // unicode id
+                [ ' a.begin ', 2 ],  // whitespace
+                [ 'a\\.b.begin', 2 ], // escaping
+                [ 'a\\-b.begin', 2 ], // escaping
+                [ 'a:b.begin', 2 ],
+                // Invalid
+                [ '-a.begin', 'notok' ], // invalid XML ID
+                [ '\\-a.begin', 'notok' ], // invalid XML ID
+                [ '0.begin', 'notok' ], // invalid XML ID
+                [ '\xB7.begin', 'notok' ], // invalid XML ID
+                [ '\x7B.begin', 'notok' ], // invalid XML ID
+                [ '.begin', 'notok' ],
+                [ '  .end  ', 'notok' ],
+                [ 'a.begin-5a', 'notok' ],
+                // Offsets
+                [ ' a.begin + 1min', 2 + 60 ],
+                [ ' a.begin-0.5s', 1.5 ],
+              ];
+  for (var i = 0; i < specs.length; i++) {
+    var spec = specs[i][0];
+    var expected = specs[i][1];
+    anim.setAttribute('begin', spec);
+    try {
+      if (typeof(expected) == 'number') {
+        is(anim.getStartTime(), expected,
+           "Unexpected start time with spec: " + spec);
+      } else if (expected == 'todo') {
+        todo_is(anim.getStartTime(), 2,"Unexpected success with spec: " + spec);
+      } else {
+        anim.getStartTime();
+        ok(false, "Unexpected success with spec: " + spec);
+      }
+    } catch(e) {
+      if (e.name == "InvalidStateError" &&
+          e.code == DOMException.INVALID_STATE_ERR) {
+        if (typeof(expected) == 'number')
+          ok(false, "Failed with spec: " + spec);
+        else if (expected == 'todo')
+          todo(false, "Yet to implement: " + spec);
+        else
+          ok(true);
+      } else {
+        ok(false, "Unexpected exception: " + e + "(with spec: " + spec + ")");
+      }
+    }
+  }
+
+  anim.remove();
+}
+
+function testChangeId() {
+  var anim = createAnim();
+
+  anim.setAttribute('begin', 'a.begin');
+  is(anim.getStartTime(), 2, "Unexpected start time.");
+
+  var a = getElement('a');
+  a.setAttribute('id', 'a1');
+  ok(noStart(anim), "Unexpected return value after changing target ID.");
+
+  a.setAttribute('id', 'a');
+  is(anim.getStartTime(), 2,
+     "Unexpected start time after resetting target ID.");
+
+  anim.remove();
+}
+
+function testRemoveTimebase() {
+  var anim = createAnim();
+  anim.setAttribute('begin', 'a.begin');
+  ok(!noStart(anim), "Unexpected start time before removing timebase.");
+
+  var circle = getElement('circle');
+  var a = getElement('a');
+  // Sanity check
+  is(a, circle.firstElementChild, "Unexpected document structure");
+
+  // Remove timebase
+  a.remove();
+  ok(noStart(anim), "Unexpected start time after removing timebase.");
+
+  // Reinsert timebase
+  circle.insertBefore(a, circle.firstElementChild);
+  ok(!noStart(anim), "Unexpected start time after re-inserting timebase.");
+
+  // Remove dependent element
+  anim.remove();
+  ok(noStart(anim), "Unexpected start time after removing dependent.");
+
+  // Create a new dependent
+  var anim2 = createAnim();
+  anim2.setAttribute('begin', 'a.begin');
+  is(anim2.getStartTime(), 2,
+     "Unexpected start time after adding new dependent.");
+}
+
+function createAnim() {
+  const svgns="http://www.w3.org/2000/svg";
+  var anim = document.createElementNS(svgns,'animate');
+  anim.setAttribute('attributeName','cx');
+  anim.setAttribute('from','0');
+  anim.setAttribute('to','100');
+  anim.setAttribute('begin','indefinite');
+  anim.setAttribute('dur','1s');
+  return getElement('circle').appendChild(anim);
+}
+
+function noStart(elem) {
+  var exceptionCaught = false;
+
+  try {
+    elem.getStartTime();
+  } catch(e) {
+    exceptionCaught = true;
+    is (e.name, "InvalidStateError",
+        "Unexpected exception from getStartTime.");
+    is (e.code, DOMException.INVALID_STATE_ERR,
+        "Unexpected exception code from getStartTime.");
+  }
+
+  return exceptionCaught;
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilTextZoom.xhtml b/dom/smil/test/test_smilTextZoom.xhtml
new file mode 100644
index 0000000000..5f65bd778e
--- /dev/null
+++ b/dom/smil/test/test_smilTextZoom.xhtml
@@ -0,0 +1,99 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL Animation Behavior with textZoom</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+  <svg xmlns="http://www.w3.org/2000/svg" width="300px" height="200px"
+       onload="this.pauseAnimations()">
+    <text y="100px" x="0px" style="font-size: 5px">
+      abc
+      <animate attributeName="font-size" attributeType="CSS" fill="freeze"
+               from="20px" to="40px" begin="1s" dur="1s"/>
+    </text>
+    <rect y="100px" x="50px" style="stroke-width: 5px">
+      <animate attributeName="stroke-width" attributeType="CSS" fill="freeze"
+               from="20px" to="40px" begin="1s" dur="1s"/>
+    </rect>
+  </svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+SimpleTest.waitForExplicitFinish();
+
+// Helper function
+function verifyStyle(aNode, aPropertyName, aExpectedVal)
+{
+  var computedVal = SMILUtil.getComputedStyleSimple(aNode, aPropertyName);
+
+  // Bug 1379908: The computed value of stroke-* properties should be
+  // serialized with px units, but currently Gecko and Servo don't do that
+  // when animating these values.
+  if ('stroke-width' == aPropertyName) {
+    var expectedVal = SMILUtil.stripPx(aExpectedVal);
+    var unitlessComputedVal = SMILUtil.stripPx(computedVal);
+    is(unitlessComputedVal, expectedVal, "computed value of " + aPropertyName);
+    return;
+  }
+  is(computedVal, aExpectedVal, "computed value of " + aPropertyName);
+}
+
+function main()
+{
+  // Start out pause
+  var svg = SMILUtil.getSVGRoot();
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  // Set text zoom to 2x
+  var origTextZoom =  SpecialPowers.getTextZoom(window);
+  SpecialPowers.setTextZoom(window, 2);
+
+  try {
+    // Verify computed style values at various points during animation.
+    // * Correct behavior is for the computed values of 'font-size' to be
+    // the same as their corresponding specified values, since text zoom
+    // should not affect SVG text elements.
+    // * I also include tests for an identical animation of the "stroke-width"
+    // property, which should _not_ be affected by textZoom.
+    var text = document.getElementsByTagName("text")[0];
+    var rect = document.getElementsByTagName("rect")[0];
+
+    verifyStyle(text, "font-size",    "5px");
+    verifyStyle(rect, "stroke-width", "5px");
+    svg.setCurrentTime(1);
+    verifyStyle(text, "font-size",    "20px");
+    verifyStyle(rect, "stroke-width", "20px");
+    svg.setCurrentTime(1.5);
+    verifyStyle(text, "font-size",    "30px");
+    verifyStyle(rect, "stroke-width", "30px");
+    svg.setCurrentTime(2);
+    verifyStyle(text, "font-size",    "40px");
+    verifyStyle(rect, "stroke-width", "40px");
+    svg.setCurrentTime(3);
+    verifyStyle(text, "font-size",    "40px");
+    verifyStyle(rect, "stroke-width", "40px");
+  } catch (e) {
+    // If anything goes wrong, make sure we restore textZoom before bubbling
+    // the exception upwards, so that we don't mess up subsequent tests.
+    SpecialPowers.setTextZoom(window, origTextZoom);
+
+    throw e;
+  }
+
+  // We're done! Restore original text-zoom before finishing
+  SpecialPowers.setTextZoom(window, origTextZoom);
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilTiming.xhtml b/dom/smil/test/test_smilTiming.xhtml
new file mode 100644
index 0000000000..0dc8525382
--- /dev/null
+++ b/dom/smil/test/test_smilTiming.xhtml
@@ -0,0 +1,291 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL timing</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="-100" cy="20" r="15" fill="blue" id="circle"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL timing **/
+
+/* Global Variables */
+const svgns = "http://www.w3.org/2000/svg";
+var gSvg    = document.getElementById("svg");
+var gCircle = document.getElementById('circle');
+
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  ok(gSvg.animationsPaused(), "should be paused by <svg> load handler");
+  is(gSvg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var testCases = Array();
+
+  const secPerMin = 60;
+  const secPerHour = secPerMin * 60;
+
+  // In the following tests that compare start times, getStartTime will round
+  // the start time to three decimal places since we expect our implementation
+  // to be millisecond accurate.
+
+  // Offset syntax
+  // -- Basic tests, sign and whitespace
+  testCases.push(StartTimeTest('3s', 3));
+  testCases.push(StartTimeTest('0s', 0));
+  testCases.push(StartTimeTest('+2s', 2));
+  testCases.push(StartTimeTest('-1s\t\r', -1));
+  testCases.push(StartTimeTest('- 1s', -1));
+  testCases.push(StartTimeTest('  -1s', -1));
+  testCases.push(StartTimeTest(' - 1s', -1));
+  testCases.push(StartTimeTest(' \t\n\r-1s', -1));
+  testCases.push(StartTimeTest('+\n5s', 5));
+  testCases.push(StartTimeTest('-\n5s', -5));
+  testCases.push(StartTimeTest('\t 5s', 5));
+  // -- These tests are from SMILANIM 3.6.7
+  testCases.push(StartTimeTest('02:30:03', 2*secPerHour + 30*secPerMin + 3));
+  testCases.push(StartTimeTest('50:00:10.25', 50*secPerHour + 10.25));
+  testCases.push(StartTimeTest('02:33', 2*secPerMin + 33));
+  testCases.push(StartTimeTest('00:10.5', 10.5));
+  testCases.push(StartTimeTest('3.2h', 3.2*secPerHour));
+  testCases.push(StartTimeTest('45min', 45*secPerMin));
+  testCases.push(StartTimeTest('30s', 30));
+  testCases.push(StartTimeTest('5ms', 0.005));
+  testCases.push(StartTimeTest('12.467', 12.467));
+  testCases.push(StartTimeTest('00.5s', 0.5));
+  testCases.push(StartTimeTest('00:00.005', 0.005));
+  // -- Additional tests
+  testCases.push(StartTimeTest('61:59:59', 61*secPerHour + 59*secPerMin + 59));
+  testCases.push(StartTimeTest('02:59.999999999999999999999', 3*secPerMin));
+  testCases.push(StartTimeTest('1234:23:45',
+                               1234*secPerHour + 23*secPerMin + 45));
+  testCases.push(StartTimeTest('61min', 61*secPerMin));
+  testCases.push(StartTimeTest('0:30:03', 30*secPerMin + 3));
+  // -- Fractional precision
+  testCases.push(StartTimeTest('25.4567', 25.457));
+  testCases.push(StartTimeTest('0.123456789', 0.123));
+  testCases.push(StartTimeTest('0.00000000000000000000001', 0));
+  testCases.push(StartTimeTest('-0.00000000000000000000001', 0));
+  testCases.push(StartTimeTest('0.0009', 0.001));
+  testCases.push(StartTimeTest('0.99999999999999999999999999999999999999', 1));
+  testCases.push(StartTimeTest('23.4567ms', 0.023));
+  testCases.push(StartTimeTest('23.7ms', 0.024));
+  // -- Test errors
+  testCases.push(StartTimeTest(' + +3s', 'none'));
+  testCases.push(StartTimeTest(' +-3s', 'none'));
+  testCases.push(StartTimeTest('1:12:12:12', 'none'));
+  testCases.push(StartTimeTest('4:50:60', 'none'));
+  testCases.push(StartTimeTest('4:60:0', 'none'));
+  testCases.push(StartTimeTest('4:60', 'none'));
+  testCases.push(StartTimeTest('4:-1:00', 'none'));
+  testCases.push(StartTimeTest('4 5m', 'none'));
+  testCases.push(StartTimeTest('4 5ms', 'none'));
+  testCases.push(StartTimeTest('02:3:03', 'none'));
+  testCases.push(StartTimeTest('45.7 s', 'none'));
+  testCases.push(StartTimeTest(' 3 h ', 'none'));
+  testCases.push(StartTimeTest('2:33 ', 'none'));
+  testCases.push(StartTimeTest('02:33 2', 'none'));
+  testCases.push(StartTimeTest('\u000B 02:33', 'none'));
+  testCases.push(StartTimeTest('h', 'none'));
+  testCases.push(StartTimeTest('23.s', 'none'));
+  testCases.push(StartTimeTest('23.', 'none'));
+  testCases.push(StartTimeTest('23.54.2s', 'none'));
+  testCases.push(StartTimeTest('23sec', 'none'));
+  testCases.push(StartTimeTest('five', 'none'));
+  testCases.push(StartTimeTest('', 'none'));
+  testCases.push(StartTimeTest('02:33s', 'none'));
+  testCases.push(StartTimeTest('02:33 s', 'none'));
+  testCases.push(StartTimeTest('2.54e6', 'none'));
+  testCases.push(StartTimeTest('02.5:33', 'none'));
+  testCases.push(StartTimeTest('2:-45:33', 'none'));
+  testCases.push(StartTimeTest('2:4.5:33', 'none'));
+  testCases.push(StartTimeTest('45m', 'none'));
+  testCases.push(StartTimeTest(':20:30', 'none'));
+  testCases.push(StartTimeTest('1.5:30', 'none'));
+  testCases.push(StartTimeTest('15:-30', 'none'));
+  testCases.push(StartTimeTest('::30', 'none'));
+  testCases.push(StartTimeTest('15:30s', 'none'));
+  testCases.push(StartTimeTest('2:1.:30', 'none'));
+  testCases.push(StartTimeTest('2:.1:30', 'none'));
+  testCases.push(StartTimeTest('2.0:15:30', 'none'));
+  testCases.push(StartTimeTest('2.:15:30', 'none'));
+  testCases.push(StartTimeTest('.2:15:30', 'none'));
+  testCases.push(StartTimeTest('70:15', 'none'));
+  testCases.push(StartTimeTest('media', 'none'));
+  testCases.push(StartTimeTest('5mi', 'none'));
+  testCases.push(StartTimeTest('5hours', 'none'));
+  testCases.push(StartTimeTest('h05:30', 'none'));
+  testCases.push(StartTimeTest('05:40\x9A', 'none'));
+  testCases.push(StartTimeTest('05:40\u30D5', 'none'));
+  testCases.push(StartTimeTest('05:40β', 'none'));
+
+  // List syntax
+  testCases.push(StartTimeTest('3', 3));
+  testCases.push(StartTimeTest('3;', 3));
+  testCases.push(StartTimeTest('3; ', 3));
+  testCases.push(StartTimeTest('3 ; ', 3));
+  testCases.push(StartTimeTest('3;;', 3));
+  testCases.push(StartTimeTest('3;; ', 3));
+  testCases.push(StartTimeTest(';3', 3));
+  testCases.push(StartTimeTest(' ;3', 3));
+  testCases.push(StartTimeTest('3;4', 3));
+  testCases.push(StartTimeTest(' 3 ; 4 ', 3));
+
+  // List syntax on end times
+  testCases.push({
+    'attr' : { 'begin': '0s',
+               'end': '1s; 2s' },
+    'times': [ [ 0, 0 ],
+               [ 1, -100 ] ]
+  });
+  testCases.push({
+    'attr' : { 'begin': '0s',
+               'end': '1s; 2s; ' },
+    'times': [ [ 0, 0 ],
+               [ 1, -100 ] ]
+  });
+  testCases.push({
+    'attr' : { 'begin': '0s',
+               'end': '3s; 2s' },
+    'times': [ [ 0, 0 ],
+               [ 1, 10 ],
+               [ 2, -100 ] ]
+  });
+
+  // Simple case
+  testCases.push({
+    'attr' : { 'begin': '3s' },
+    'times': [ [ 0, -100 ],
+               [ 4, 10 ] ]
+  });
+
+  // Multiple begins
+  testCases.push({
+    'attr' : { 'begin': '2s; 6s',
+               'dur': '2s' },
+    'times': [ [ 0, -100 ],
+               [ 3, 50 ],
+               [ 4, -100 ],
+               [ 7, 50 ],
+               [ 8, -100 ] ]
+  });
+
+  // Negative begins
+  testCases.push({
+    'attr' : { 'begin': '-3s; 1s ; 4s',
+               'dur': '2s ',
+               'fill': 'freeze' },
+    'times': [ [ 0, -100 ],
+               [ 0.5, -100 ],
+               [ 1, 0 ],
+               [ 2, 50 ],
+               [ 3, 100 ],
+               [ 5, 50 ] ]
+  });
+
+  // Sorting
+  testCases.push({
+    'attr' : { 'begin': '-3s; 110s; 1s; 4s; -5s; -10s',
+               'end': '111s; -5s; -15s; 6s; -5s; 1.2s',
+               'dur': '2s ',
+               'fill': 'freeze' },
+    'times': [ [ 0, -100 ],
+               [ 1, 0 ],
+               [ 2, 10 ],
+               [ 4, 0 ],
+               [ 5, 50 ],
+               [ 109, 100 ],
+               [ 110, 0 ],
+               [ 112, 50 ] ]
+  });
+
+  for (var i = 0; i < testCases.length; i++) {
+    gSvg.setCurrentTime(0);
+    var test = testCases[i];
+
+    // Generate string version of params for output messages
+    var params = "";
+    for (var name in test.attr) {
+      params += name + '="' + test.attr[name] + '" ';
+    }
+    params = params.trim();
+
+    // Create animation elements
+    var anim = createAnim(test.attr);
+
+    // Run samples
+    if ('times' in test) {
+      for (var j = 0; j < test.times.length; j++) {
+        var curSample = test.times[j];
+        checkSample(curSample[0], curSample[1], params);
+      }
+    }
+
+    // Check start time
+    if ('startTime' in test) {
+      is(getStartTime(anim), test.startTime,
+         "Got unexpected start time for " + params);
+    }
+
+    anim.remove();
+  }
+
+  SimpleTest.finish();
+}
+
+function createAnim(attr) {
+  var anim = document.createElementNS(svgns,'animate');
+  anim.setAttribute('attributeName','cx');
+  anim.setAttribute('from','0');
+  anim.setAttribute('to','100');
+  anim.setAttribute('dur','10s');
+  anim.setAttribute('begin','indefinite');
+  for (name in attr) {
+    anim.setAttribute(name, attr[name]);
+  }
+  return gCircle.appendChild(anim);
+}
+
+function checkSample(time, expectedValue, params) {
+  gSvg.setCurrentTime(time);
+  var msg = "Unexpected sample value for " + params +
+    " at t=" + time + ": ";
+  is(gCircle.cx.animVal.value, expectedValue);
+}
+
+function getStartTime(anim) {
+  var startTime;
+  try {
+    startTime = anim.getStartTime();
+    // We round start times to 3 decimal places to make comparisons simpler
+    startTime = parseFloat(startTime.toFixed(3));
+  } catch(e) {
+    if (e.name == "InvalidStateError" &&
+        e.code == DOMException.INVALID_STATE_ERR) {
+      startTime = 'none';
+    } else {
+      ok(false, "Unexpected exception: " + e);
+    }
+  }
+  return startTime;
+}
+
+function StartTimeTest(beginSpec, expectedStartTime) {
+  return { 'attr'     : { 'begin': beginSpec },
+           'startTime': expectedStartTime };
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilTimingZeroIntervals.xhtml b/dom/smil/test/test_smilTimingZeroIntervals.xhtml
new file mode 100644
index 0000000000..d54b74600b
--- /dev/null
+++ b/dom/smil/test/test_smilTimingZeroIntervals.xhtml
@@ -0,0 +1,285 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL timing with zero-duration intervals</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="-100" cy="20" r="15" fill="blue" id="circle"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL timing with zero-duration intervals **/
+
+/* Global Variables */
+const svgns="http://www.w3.org/2000/svg";
+var svg = document.getElementById("svg");
+var circle = document.getElementById('circle');
+
+SimpleTest.waitForExplicitFinish();
+
+function createAnim() {
+  var anim = document.createElementNS(svgns,'animate');
+  anim.setAttribute('attributeName','cx');
+  anim.setAttribute('from','0');
+  anim.setAttribute('to','100');
+  anim.setAttribute('dur','10s');
+  anim.setAttribute('begin','indefinite');
+  return circle.appendChild(anim);
+}
+
+function removeAnim(anim) {
+  anim.remove();
+}
+
+function main() {
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var tests =
+    [ testZeroDurationIntervalsA,
+      testZeroDurationIntervalsB,
+      testZeroDurationIntervalsC,
+      testZeroDurationIntervalsD,
+      testZeroDurationIntervalsE,
+      testZeroDurationIntervalsF,
+      testZeroDurationIntervalsG,
+      testZeroDurationIntervalsH,
+      testZeroDurationIntervalsI,
+      testZeroDurationIntervalsJ,
+      testZeroDurationIntervalsK,
+      testZeroDurationIntervalsL,
+      testZeroDurationIntervalsM,
+      testZeroDurationIntervalsN,
+      testZeroDurationIntervalsO
+    ];
+  for (var i = 0; i < tests.length; i++) {
+    var anim = createAnim();
+    svg.setCurrentTime(0);
+    tests[i](anim);
+    removeAnim(anim);
+  }
+  SimpleTest.finish();
+}
+
+function checkSample(time, expectedValue) {
+  svg.setCurrentTime(time);
+  is(circle.cx.animVal.value, expectedValue);
+}
+
+function testZeroDurationIntervalsA(anim) {
+  // The zero-duration interval should play, followed by a second interval
+  // starting at the same point. There is no end for the interval
+  // at 4s so it should not play.
+  anim.setAttribute('begin', '1s ;4s');
+  anim.setAttribute('end', '1s; 2s');
+  anim.setAttribute('dur', '2s ');
+  anim.setAttribute('fill', 'freeze');
+  checkSample(0,-100);
+  checkSample(1,0);
+  checkSample(1.1,5);
+  checkSample(2,50);
+  checkSample(3,50);
+  checkSample(4,50);
+  checkSample(5,50);
+  checkSample(6,50);
+}
+
+function testZeroDurationIntervalsB(anim) {
+  // This interval should however actually restart as there is a valid end-point
+  anim.setAttribute('begin', '1s ;4s');
+  anim.setAttribute('end', '1.1s; indefinite');
+  anim.setAttribute('dur', '2s ');
+  anim.setAttribute('fill', 'freeze');
+  checkSample(0,-100);
+  checkSample(1,0);
+  checkSample(1.1,5);
+  checkSample(2,5);
+  checkSample(4,0);
+  checkSample(5,50);
+}
+
+function testZeroDurationIntervalsC(anim) {
+  // -0.5s has already been used as the endpoint of one interval so don't use it
+  // a second time
+  anim.setAttribute('begin', '-2s; -0.5s');
+  anim.setAttribute('end', '-0.5s; 1s');
+  anim.setAttribute('dur', '2s');
+  anim.setAttribute('fill', 'freeze');
+  checkSample(0,25);
+  checkSample(1.5,75);
+}
+
+function testZeroDurationIntervalsD(anim) {
+  // Two end points that could make a zero-length interval
+  anim.setAttribute('begin', '-2s; -0.5s');
+  anim.setAttribute('end', '-0.5s; -0.5s; 1s');
+  anim.setAttribute('dur', '2s');
+  anim.setAttribute('fill', 'freeze');
+  checkSample(0,25);
+  checkSample(1.5,75);
+}
+
+function testZeroDurationIntervalsE(anim) {
+  // Should give us 1s-1s, 1s-5s
+  anim.setAttribute('begin', '1s');
+  anim.setAttribute('end', '1s; 5s');
+  anim.setAttribute('fill', 'freeze');
+  is(anim.getStartTime(),1);
+  checkSample(0,-100);
+  checkSample(1,0);
+  checkSample(6,40);
+}
+
+function testZeroDurationIntervalsF(anim) {
+  // Should give us 1s-1s
+  anim.setAttribute('begin', '1s');
+  anim.setAttribute('end', '1s');
+  anim.setAttribute('fill', 'freeze');
+  is(anim.getStartTime(),1);
+  checkSample(0,-100);
+  checkSample(1,0);
+  checkSample(2,0);
+  try {
+    anim.getStartTime();
+    ok(false, "Failed to throw exception when there's no current interval.");
+  } catch (e) { }
+}
+
+function testZeroDurationIntervalsG(anim) {
+  // Test a non-zero interval after a zero interval
+  // Should give us 1-2s, 3-3s, 3-4s
+  anim.setAttribute('begin', '1s; 3s');
+  anim.setAttribute('end', '3s; 5s');
+  anim.setAttribute('dur', '1s');
+  anim.setAttribute('fill', 'freeze');
+  checkSample(0,-100);
+  checkSample(1,0);
+  checkSample(2,100);
+  checkSample(3,0);
+  checkSample(5,100);
+}
+
+function testZeroDurationIntervalsH(anim) {
+  // Test multiple non-adjacent zero-intervals
+  // Should give us 1-1s, 1-2s, 3-3s, 3-4s
+  anim.setAttribute('begin', '1s; 3s');
+  anim.setAttribute('end', '1s; 3s; 5s');
+  anim.setAttribute('dur', '1s');
+  anim.setAttribute('fill', 'freeze');
+  checkSample(0,-100);
+  checkSample(1,0);
+  checkSample(2,100);
+  checkSample(3,0);
+  checkSample(5,100);
+}
+
+function testZeroDurationIntervalsI(anim) {
+  // Test skipping values that are the same
+  // Should give us 1-1s, 1-2s
+  anim.setAttribute('begin', '1s; 1s');
+  anim.setAttribute('end', '1s; 1s; 2s');
+  anim.setAttribute('fill', 'freeze');
+  is(anim.getStartTime(),1);
+  checkSample(0,-100);
+  checkSample(1,0);
+  checkSample(2,10);
+  checkSample(3,10);
+}
+
+function testZeroDurationIntervalsJ(anim) {
+  // Should give us 0-0.5s, 1-1s, 1-3s
+  anim.setAttribute('begin', '0s; 1s; 1s');
+  anim.setAttribute('end', '1s; 3s');
+  anim.setAttribute('dur', '0.5s');
+  anim.setAttribute('fill', 'freeze');
+  is(anim.getStartTime(),0);
+  checkSample(0,0);
+  checkSample(0.6,100);
+  checkSample(1,0);
+  checkSample(2,100);
+}
+
+function testZeroDurationIntervalsK(anim) {
+  // Should give us -0.5-1s
+  anim.setAttribute('begin', '-0.5s');
+  anim.setAttribute('end', '-0.5s; 1s');
+  anim.setAttribute('fill', 'freeze');
+  is(anim.getStartTime(),-0.5);
+  checkSample(0,5);
+  checkSample(1,15);
+  checkSample(2,15);
+}
+
+function testZeroDurationIntervalsL(anim) {
+  // Test that multiple end values are ignored
+  // Should give us 1-1s, 1-3s
+  anim.setAttribute('begin', '1s');
+  anim.setAttribute('end', '1s; 1s; 1s; 3s');
+  anim.setAttribute('fill', 'freeze');
+  is(anim.getStartTime(),1);
+  checkSample(0,-100);
+  checkSample(1,0);
+  checkSample(2,10);
+  checkSample(4,20);
+}
+
+function testZeroDurationIntervalsM(anim) {
+  // Test 0-duration interval at start
+  anim.setAttribute('begin', '0s');
+  anim.setAttribute('end', '0s');
+  anim.setAttribute('fill', 'freeze');
+  try {
+    anim.getStartTime();
+    ok(false, "Failed to throw exception when there's no current interval.");
+  } catch (e) { }
+  checkSample(0,0);
+  checkSample(1,0);
+}
+
+function testZeroDurationIntervalsN(anim) {
+  // Test 0-active-duration interval at start (different code path to above)
+  anim.setAttribute('begin', '0s');
+  anim.setAttribute('repeatDur', '0s');
+  anim.setAttribute('fill', 'freeze');
+  try {
+    anim.getStartTime();
+    ok(false, "Failed to throw exception when there's no current interval.");
+  } catch (e) { }
+  checkSample(0,0);
+  checkSample(1,0);
+}
+
+function testZeroDurationIntervalsO(anim) {
+  // Make a zero-duration interval by constraining the active duration
+  // We should not loop infinitely but should look for the next begin time after
+  // that (in this case that is 2s, which would otherwise have been skipped
+  // because restart=whenNotActive)
+  // Should give us 1-1s, 2-2s
+  anim.setAttribute('begin', '1s; 2s');
+  anim.setAttribute('repeatDur', '0s');
+  anim.setAttribute('restart', 'whenNotActive');
+  anim.setAttribute('fill', 'freeze');
+  is(anim.getStartTime(),1);
+  checkSample(0,-100);
+  checkSample(1,0);
+  checkSample(1.5,0);
+  checkSample(3,0);
+  try {
+    anim.getStartTime();
+    ok(false, "Failed to throw exception when there's no current interval.");
+  } catch (e) { }
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilUpdatedInterval.xhtml b/dom/smil/test/test_smilUpdatedInterval.xhtml
new file mode 100644
index 0000000000..3045a815de
--- /dev/null
+++ b/dom/smil/test/test_smilUpdatedInterval.xhtml
@@ -0,0 +1,64 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Tests updated intervals</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px"
+     onload="this.pauseAnimations()">
+  <circle cx="20" cy="20" r="15" fill="blue" id="circle">
+    <animate attributeName="cx" from="0" to="100" begin="2s" dur="4s"
+             id="anim1" attributeType="XML"/>
+  </circle>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Tests for updated intervals  **/
+
+/* Global Variables */
+SimpleTest.waitForExplicitFinish();
+
+function main() {
+  var svg = document.getElementById("svg");
+  ok(svg.animationsPaused(), "should be paused by <svg> load handler");
+  is(svg.getCurrentTime(), 0, "should be paused at 0 in <svg> load handler");
+
+  var anim = document.getElementById("anim1");
+
+  // Check regular operation
+  svg.setCurrentTime(3);
+  is(anim.getStartTime(), 2, "Unexpected initial start time");
+
+  // Add an instance time before the current interval at t=1s
+  anim.beginElementAt(-2);
+
+  // We shouldn't change the begin time
+  is(anim.getStartTime(), 2, "Start time shouldn't have changed");
+
+  // Or the end--that is, if we go to t=5.5 we should still be running
+  svg.setCurrentTime(5.5);
+  try {
+    is(anim.getSimpleDuration(), 4, "Simple duration shouldn't have changed");
+    is(anim.getStartTime(), 2, "Start time shouldn't have changed after seek");
+  } catch (e) {
+    if (e.name != "InvalidStateError" ||
+        e.code != DOMException.INVALID_STATE_ERR)
+      throw e;
+    ok(false, "Animation ended too early, even though begin time and " +
+      "simple duration didn't change");
+  }
+
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilValues.xhtml b/dom/smil/test/test_smilValues.xhtml
new file mode 100644
index 0000000000..b25a153472
--- /dev/null
+++ b/dom/smil/test/test_smilValues.xhtml
@@ -0,0 +1,171 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL values</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank"
+  href="https://bugzilla.mozilla.org/show_bug.cgi?id=557885">Mozilla Bug
+  474742</a>
+<p id="display"></p>
+<div id="content">
+<svg id="svg" xmlns="http://www.w3.org/2000/svg" width="120px" height="120px">
+  <circle cx="-100" cy="20" r="15" fill="blue" id="circle"/>
+</svg>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL values **/
+
+var gSvg = document.getElementById("svg");
+SimpleTest.waitForExplicitFinish();
+
+function main()
+{
+  gSvg.pauseAnimations();
+
+  var testCases = Array();
+
+  // Single value
+  testCases.push({
+    'attr' : { 'values': 'a' },
+    'times': [ [ 0, 'a' ] ]
+  });
+
+  // The parsing below is based on the following discussion:
+  //
+  //   http://lists.w3.org/Archives/Public/www-svg/2011Nov/0136.html
+  //
+  // In summary:
+  // * Values lists are semi-colon delimited and semi-colon terminated.
+  // * However, if there are extra non-whitespace characters after the final
+  //   semi-colon then there's an implied semi-colon at the end.
+  //
+  // This differs to what is specified in SVG 1.1 but is consistent with the
+  // majority of browsers and with existing content (particularly that generated
+  // by Ikivo Animator).
+
+  // Trailing semi-colon
+  testCases.push({
+    'attr' : { 'values': 'a;' },
+    'times': [ [ 0, 'a' ], [ 10, 'a' ] ]
+  });
+
+  // Trailing semi-colon + whitespace
+  testCases.push({
+    'attr' : { 'values': 'a; ' },
+    'times': [ [ 0, 'a' ], [ 10, 'a' ] ]
+  });
+
+  // Whitespace + trailing semi-colon
+  testCases.push({
+    'attr' : { 'values': 'a ;' },
+    'times': [ [ 0, 'a' ], [ 10, 'a' ] ]
+  });
+
+  // Empty at end
+  testCases.push({
+    'attr' : { 'values': 'a;;' },
+    'times': [ [ 0, 'a' ], [ 5, '' ], [ 10, '' ] ]
+  });
+
+  // Empty at end + whitespace
+  testCases.push({
+    'attr' : { 'values': 'a;; ' },
+    'times': [ [ 0, 'a' ], [ 4, 'a' ], [ 5, '' ], [ 10, '' ] ]
+  });
+
+  // Empty in middle
+  testCases.push({
+    'attr' : { 'values': 'a;;b' },
+    'times': [ [ 0, 'a' ], [ 5, '' ], [ 10, 'b' ] ]
+  });
+
+  // Empty in middle + trailing semi-colon
+  testCases.push({
+    'attr' : { 'values': 'a;;b;' },
+    'times': [ [ 0, 'a' ], [ 5, '' ], [ 10, 'b' ] ]
+  });
+
+  // Whitespace in middle
+  testCases.push({
+    'attr' : { 'values': 'a; ;b' },
+    'times': [ [ 0, 'a' ], [ 5, '' ], [ 10, 'b' ] ]
+  });
+
+  // Empty at start
+  testCases.push({
+    'attr' : { 'values': ';a' },
+    'times': [ [ 0, '' ], [ 5, 'a' ], [ 10, 'a' ] ]
+  });
+
+  // Whitespace at start
+  testCases.push({
+    'attr' : { 'values': ' ;a' },
+    'times': [ [ 0, '' ], [ 5, 'a' ], [ 10, 'a' ] ]
+  });
+
+  // Embedded whitespace
+  testCases.push({
+    'attr' : { 'values': ' a b ; c d ' },
+    'times': [ [ 0, 'a b' ], [ 5, 'c d' ], [ 10, 'c d' ] ]
+  });
+
+  // Whitespace only
+  testCases.push({
+    'attr' : { 'values': '  ' },
+    'times': [ [ 0, '' ], [ 10, '' ] ]
+  });
+
+  for (var i = 0; i < testCases.length; i++) {
+    gSvg.setCurrentTime(0);
+    var test = testCases[i];
+
+    // Create animation elements
+    var anim = createAnim(test.attr);
+
+    // Run samples
+    for (var j = 0; j < test.times.length; j++) {
+      var curSample = test.times[j];
+      gSvg.setCurrentTime(curSample[0]);
+      checkSample(anim, curSample[1], curSample[0], i);
+    }
+
+    anim.remove();
+  }
+
+  SimpleTest.finish();
+}
+
+function createAnim(attr)
+{
+  const svgns = "http://www.w3.org/2000/svg";
+  var anim = document.createElementNS(svgns, 'animate');
+  anim.setAttribute('attributeName','class');
+  anim.setAttribute('dur','10s');
+  anim.setAttribute('begin','0s');
+  anim.setAttribute('fill','freeze');
+  for (name in attr) {
+    anim.setAttribute(name, attr[name]);
+  }
+  return document.getElementById('circle').appendChild(anim);
+}
+
+function checkSample(anim, expectedValue, sampleTime, caseNum)
+{
+  var msg = "Test case " + caseNum +
+    " (values: '" + anim.getAttribute('values') + "')," +
+    "t=" + sampleTime +
+    ": Unexpected sample value:";
+  is(typeof anim.targetElement.className, "object");
+  is(anim.targetElement.className.animVal, expectedValue, msg);
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/smil/test/test_smilWithTransition.html b/dom/smil/test/test_smilWithTransition.html
new file mode 100644
index 0000000000..4378841f50
--- /dev/null
+++ b/dom/smil/test/test_smilWithTransition.html
@@ -0,0 +1,14 @@
+<!doctype html>
+<meta charset=utf-8>
+<head>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<pre id="test">
+<script>
+'use strict';
+
+SimpleTest.waitForExplicitFinish();
+window.open("file_smilWithTransition.html");
+</script>
+</html>
diff --git a/dom/smil/test/test_smilWithXlink.xhtml b/dom/smil/test/test_smilWithXlink.xhtml
new file mode 100644
index 0000000000..46ac0f12ef
--- /dev/null
+++ b/dom/smil/test/test_smilWithXlink.xhtml
@@ -0,0 +1,47 @@
+<html xmlns="http://www.w3.org/1999/xhtml">

+<head>

+  <title>Test for animate with xlink:href attribute.</title>

+  <script src="/tests/SimpleTest/SimpleTest.js"></script>

+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />

+  <style>

+    div#target {

+      width: 300px;

+      height: 100px;

+      background-color: red;

+    }

+  </style>

+</head>

+<body>

+<p id="display"></p>

+<div id="target"></div>

+<svg xmlns="http://www.w3.org/2000/svg"

+     xmlns:xlink="http://www.w3.org/1999/xlink"

+     id="svg">

+  <animate xlink:href="#target"

+           attributeName="width" from="0" to="200" dur="10s" fill="freeze"/>

+</svg>

+<pre id="test">

+<script class="testbody" type="text/javascript">

+<![CDATA[

+SimpleTest.waitForExplicitFinish();

+

+function runTest() {

+  var svg = document.getElementById("svg");

+  var target = document.getElementById("target");

+

+  svg.pauseAnimations();

+  svg.setCurrentTime(5);

+

+  var cs = getComputedStyle(target);

+  is(cs.width, "100px", "SMIL should affect outer element.");

+

+  SimpleTest.finish();

+}

+

+window.addEventListener("load", runTest);

+

+]]>

+</script>

+</pre>

+</body>

+</html>

diff --git a/dom/smil/test/test_smilXHR.xhtml b/dom/smil/test/test_smilXHR.xhtml
new file mode 100644
index 0000000000..eb0f84268c
--- /dev/null
+++ b/dom/smil/test/test_smilXHR.xhtml
@@ -0,0 +1,88 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <title>Test for SMIL Behavior in Data Documents</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="smilTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=529387">Mozilla Bug 529387</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+<![CDATA[
+/** Test for SMIL Behavior in Data Documents, with XMLHttpRequest **/
+
+SimpleTest.waitForExplicitFinish();
+
+function tryPausing(svg) {
+  // Check that pausing has no effect
+  ok(!svg.animationsPaused(),
+     "shouldn't be paused (because we shouldn't have even started");
+  svg.pauseAnimations();
+  ok(!svg.animationsPaused(), "attempts to pause should have no effect");
+  svg.unpauseAnimations();
+  ok(!svg.animationsPaused(), "still shouldn't be paused, after pause/unpause");
+}
+
+function trySeeking(svg) {
+  // Check that seeking is ineffective
+  is(svg.getCurrentTime(), 0, "should start out at time=0");
+  svg.setCurrentTime(1);
+  is(svg.getCurrentTime(), 0, "shouldn't be able to seek away from time=0");
+}
+
+function tryBeginEnd(anim) {
+  // Check that beginning / ending a particular animation element will trigger
+  // exceptions.
+  var didThrow = false;
+  ok(anim, "need a non-null animate element");
+  try {
+     anim.beginElement();
+  } catch (e) {
+    didThrow = true;
+  }
+  ok(didThrow, "beginElement should fail");
+
+  didThrow = false;
+  try {
+    anim.endElement();
+  } catch (e) {
+    didThrow = true;
+  }
+  ok(didThrow, "endElement should fail");
+}
+
+function main() {
+  var xhr = new XMLHttpRequest();
+  xhr.open("GET", "smilXHR_helper.svg", false);
+  xhr.send();
+  var xdoc = xhr.responseXML;
+
+  var svg  = xdoc.getElementById("svg");
+  var circ = xdoc.getElementById("circ");
+  var animXML = xdoc.getElementById("animXML");
+  var animCSS = xdoc.getElementById("animCSS");
+
+  tryPausing(svg);
+  trySeeking(svg);
+  tryBeginEnd(animXML);
+  tryBeginEnd(animCSS);
+
+  // Check that the actual values of our animated attr/prop aren't affected
+  is(circ.cx.animVal.value, circ.cx.baseVal.value,
+     "animation of attribute shouldn't be taking effect");
+  is(SMILUtil.getComputedStyleSimple(circ, "opacity"), "1",
+     "animation of CSS property shouldn't be taking effect");
+ 
+  SimpleTest.finish();
+}
+
+window.addEventListener("load", main);
+]]>
+</script>
+</pre>
+</body>
+</html>