Adding upstream version 86.0.1.upstream/86.0.1upstream

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

25 files changed, 4083 insertions, 0 deletions

diff --git a/gfx/layers/apz/util/APZCCallbackHelper.cpp b/gfx/layers/apz/util/APZCCallbackHelper.cpp
new file mode 100644
index 0000000000..8d5d38f0cd
--- /dev/null
+++ b/gfx/layers/apz/util/APZCCallbackHelper.cpp
@@ -0,0 +1,925 @@
+/* -*- 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 "APZCCallbackHelper.h"
+
+#include "TouchActionHelper.h"
+#include "gfxPlatform.h"  // For gfxPlatform::UseTiling
+
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/MouseEventBinding.h"
+#include "mozilla/dom/BrowserParent.h"
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/layers/LayerTransactionChild.h"
+#include "mozilla/layers/RepaintRequest.h"
+#include "mozilla/layers/ShadowLayers.h"
+#include "mozilla/layers/WebRenderLayerManager.h"
+#include "mozilla/layers/WebRenderBridgeChild.h"
+#include "mozilla/DisplayPortUtils.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/TouchEvents.h"
+#include "mozilla/ToString.h"
+#include "mozilla/ViewportUtils.h"
+#include "nsContainerFrame.h"
+#include "nsContentUtils.h"
+#include "nsIContent.h"
+#include "nsIDOMWindowUtils.h"
+#include "mozilla/dom/Document.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsIScrollableFrame.h"
+#include "nsLayoutUtils.h"
+#include "nsPrintfCString.h"
+#include "nsRefreshDriver.h"
+#include "nsString.h"
+#include "nsView.h"
+#include "Layers.h"
+
+static mozilla::LazyLogModule sApzHlpLog("apz.helper");
+#define APZCCH_LOG(...) MOZ_LOG(sApzHlpLog, LogLevel::Debug, (__VA_ARGS__))
+static mozilla::LazyLogModule sDisplayportLog("apz.displayport");
+
+namespace mozilla {
+namespace layers {
+
+using dom::BrowserParent;
+
+uint64_t APZCCallbackHelper::sLastTargetAPZCNotificationInputBlock =
+    uint64_t(-1);
+
+static ScreenMargin RecenterDisplayPort(const ScreenMargin& aDisplayPort) {
+  ScreenMargin margins = aDisplayPort;
+  margins.right = margins.left = margins.LeftRight() / 2;
+  margins.top = margins.bottom = margins.TopBottom() / 2;
+  return margins;
+}
+
+static PresShell* GetPresShell(const nsIContent* aContent) {
+  if (dom::Document* doc = aContent->GetComposedDoc()) {
+    return doc->GetPresShell();
+  }
+  return nullptr;
+}
+
+static CSSPoint ScrollFrameTo(nsIScrollableFrame* aFrame,
+                              const RepaintRequest& aRequest,
+                              bool& aSuccessOut) {
+  aSuccessOut = false;
+  CSSPoint targetScrollPosition = aRequest.GetLayoutScrollOffset();
+
+  if (!aFrame) {
+    return targetScrollPosition;
+  }
+
+  CSSPoint geckoScrollPosition =
+      CSSPoint::FromAppUnits(aFrame->GetScrollPosition());
+
+  // If the repaint request was triggered due to a previous main-thread scroll
+  // offset update sent to the APZ, then we don't need to do another scroll here
+  // and we can just return.
+  if (!aRequest.GetScrollOffsetUpdated()) {
+    return geckoScrollPosition;
+  }
+
+  // If this frame is overflow:hidden, then the expectation is that it was
+  // sized in a way that respects its scrollable boundaries. For the root
+  // frame, this means that it cannot be scrolled in such a way that it moves
+  // the layout viewport. For a non-root frame, this means that it cannot be
+  // scrolled at all.
+  //
+  // In either case, |targetScrollPosition| should be the same as
+  // |geckoScrollPosition| here.
+  //
+  // However, this is slightly racy. We query the overflow property of the
+  // scroll frame at the time the repaint request arrives at the main thread
+  // (i.e., right now), but APZ made the decision of whether or not to allow
+  // scrolling based on the information it had at the time it processed the
+  // scroll event. The overflow property could have changed at some time
+  // between the two events and so APZ may have computed a scrollable region
+  // that is larger than what is actually allowed.
+  //
+  // Currently, we allow the scroll position to change even though the frame is
+  // overflow:hidden (that is, we take |targetScrollPosition|). If this turns
+  // out to be problematic, an alternative solution would be to ignore the
+  // scroll position change (that is, use |geckoScrollPosition|).
+  if (aFrame->GetScrollStyles().mVertical == StyleOverflow::Hidden &&
+      targetScrollPosition.y != geckoScrollPosition.y) {
+    NS_WARNING(
+        nsPrintfCString(
+            "APZCCH: targetScrollPosition.y (%f) != geckoScrollPosition.y (%f)",
+            targetScrollPosition.y, geckoScrollPosition.y)
+            .get());
+  }
+  if (aFrame->GetScrollStyles().mHorizontal == StyleOverflow::Hidden &&
+      targetScrollPosition.x != geckoScrollPosition.x) {
+    NS_WARNING(
+        nsPrintfCString(
+            "APZCCH: targetScrollPosition.x (%f) != geckoScrollPosition.x (%f)",
+            targetScrollPosition.x, geckoScrollPosition.x)
+            .get());
+  }
+
+  // If the scrollable frame is currently in the middle of an async or smooth
+  // scroll then we don't want to interrupt it (see bug 961280).
+  // Also if the scrollable frame got a scroll request from a higher priority
+  // origin since the last layers update, then we don't want to push our scroll
+  // request because we'll clobber that one, which is bad.
+  bool scrollInProgress = APZCCallbackHelper::IsScrollInProgress(aFrame);
+  if (!scrollInProgress) {
+    aFrame->ScrollToCSSPixelsApproximate(targetScrollPosition,
+                                         ScrollOrigin::Apz);
+    geckoScrollPosition = CSSPoint::FromAppUnits(aFrame->GetScrollPosition());
+    aSuccessOut = true;
+  }
+  // Return the final scroll position after setting it so that anything that
+  // relies on it can have an accurate value. Note that even if we set it above
+  // re-querying it is a good idea because it may have gotten clamped or
+  // rounded.
+  return geckoScrollPosition;
+}
+
+/**
+ * Scroll the scroll frame associated with |aContent| to the scroll position
+ * requested in |aRequest|.
+ *
+ * Any difference between the requested and actual scroll positions is used to
+ * update the callback-transform stored on the content, and return a new
+ * display port.
+ */
+static DisplayPortMargins ScrollFrame(nsIContent* aContent,
+                                      const RepaintRequest& aRequest) {
+  // Scroll the window to the desired spot
+  nsIScrollableFrame* sf =
+      nsLayoutUtils::FindScrollableFrameFor(aRequest.GetScrollId());
+  if (sf) {
+    sf->ResetScrollInfoIfNeeded(aRequest.GetScrollGeneration(),
+                                aRequest.IsAnimationInProgress());
+    sf->SetScrollableByAPZ(!aRequest.IsScrollInfoLayer());
+    if (sf->IsRootScrollFrameOfDocument()) {
+      if (!APZCCallbackHelper::IsScrollInProgress(sf)) {
+        APZCCH_LOG("Setting VV offset to %s\n",
+                   ToString(aRequest.GetVisualScrollOffset()).c_str());
+        if (sf->SetVisualViewportOffset(
+                CSSPoint::ToAppUnits(aRequest.GetVisualScrollOffset()),
+                /* aRepaint = */ false)) {
+          // sf can't be destroyed if SetVisualViewportOffset returned true.
+          sf->MarkEverScrolled();
+        }
+      }
+    }
+  }
+  // sf might have been destroyed by the call to SetVisualViewportOffset, so
+  // re-get it.
+  sf = nsLayoutUtils::FindScrollableFrameFor(aRequest.GetScrollId());
+  bool scrollUpdated = false;
+  auto displayPortMargins = DisplayPortMargins::ForScrollFrame(
+      sf, aRequest.GetDisplayPortMargins(),
+      Some(aRequest.DisplayportPixelsPerCSSPixel()));
+  CSSPoint apzScrollOffset = aRequest.GetVisualScrollOffset();
+  CSSPoint actualScrollOffset = ScrollFrameTo(sf, aRequest, scrollUpdated);
+  CSSPoint scrollDelta = apzScrollOffset - actualScrollOffset;
+
+  if (scrollUpdated) {
+    if (aRequest.IsScrollInfoLayer()) {
+      // In cases where the APZ scroll offset is different from the content
+      // scroll offset, we want to interpret the margins as relative to the APZ
+      // scroll offset except when the frame is not scrollable by APZ.
+      // Therefore, if the layer is a scroll info layer, we leave the margins
+      // as-is and they will be interpreted as relative to the content scroll
+      // offset.
+      if (nsIFrame* frame = aContent->GetPrimaryFrame()) {
+        frame->SchedulePaint();
+      }
+    } else {
+      // Correct the display port due to the difference between the requested
+      // and actual scroll offsets.
+      displayPortMargins = DisplayPortMargins::FromAPZ(
+          aRequest.GetDisplayPortMargins(), apzScrollOffset, actualScrollOffset,
+          aRequest.DisplayportPixelsPerCSSPixel());
+    }
+  } else if (aRequest.IsRootContent() &&
+             apzScrollOffset != aRequest.GetLayoutScrollOffset()) {
+    // APZ uses the visual viewport's offset to calculate where to place the
+    // display port, so the display port is misplaced when a pinch zoom occurs.
+    //
+    // We need to force a display port adjustment in the following paint to
+    // account for a difference between the requested and actual scroll
+    // offsets in repaints requested by
+    // AsyncPanZoomController::NotifyLayersUpdated.
+    displayPortMargins = DisplayPortMargins::FromAPZ(
+        aRequest.GetDisplayPortMargins(), apzScrollOffset, actualScrollOffset,
+        aRequest.DisplayportPixelsPerCSSPixel());
+  } else {
+    // For whatever reason we couldn't update the scroll offset on the scroll
+    // frame, which means the data APZ used for its displayport calculation is
+    // stale. Fall back to a sane default behaviour. Note that we don't
+    // tile-align the recentered displayport because tile-alignment depends on
+    // the scroll position, and the scroll position here is out of our control.
+    // See bug 966507 comment 21 for a more detailed explanation.
+    displayPortMargins = DisplayPortMargins::ForScrollFrame(
+        sf, RecenterDisplayPort(aRequest.GetDisplayPortMargins()),
+        Some(aRequest.DisplayportPixelsPerCSSPixel()));
+  }
+
+  // APZ transforms inputs assuming we applied the exact scroll offset it
+  // requested (|apzScrollOffset|). Since we may not have, record the difference
+  // between what APZ asked for and what we actually applied, and apply it to
+  // input events to compensate.
+  // Note that if the main-thread had a change in its scroll position, we don't
+  // want to record that difference here, because it can be large and throw off
+  // input events by a large amount. It is also going to be transient, because
+  // any main-thread scroll position change will be synced to APZ and we will
+  // get another repaint request when APZ confirms. In the interval while this
+  // is happening we can just leave the callback transform as it was.
+  bool mainThreadScrollChanged =
+      sf && sf->CurrentScrollGeneration() != aRequest.GetScrollGeneration() &&
+      nsLayoutUtils::CanScrollOriginClobberApz(sf->LastScrollOrigin());
+  if (aContent && !mainThreadScrollChanged) {
+    aContent->SetProperty(nsGkAtoms::apzCallbackTransform,
+                          new CSSPoint(scrollDelta),
+                          nsINode::DeleteProperty<CSSPoint>);
+  }
+
+  return displayPortMargins;
+}
+
+static void SetDisplayPortMargins(PresShell* aPresShell, nsIContent* aContent,
+                                  const DisplayPortMargins& aDisplayPortMargins,
+                                  CSSSize aDisplayPortBase) {
+  if (!aContent) {
+    return;
+  }
+
+  bool hadDisplayPort = DisplayPortUtils::HasDisplayPort(aContent);
+  if (MOZ_LOG_TEST(sDisplayportLog, LogLevel::Debug)) {
+    if (!hadDisplayPort) {
+      mozilla::layers::ScrollableLayerGuid::ViewID viewID =
+          mozilla::layers::ScrollableLayerGuid::NULL_SCROLL_ID;
+      nsLayoutUtils::FindIDFor(aContent, &viewID);
+      MOZ_LOG(
+          sDisplayportLog, LogLevel::Debug,
+          ("APZCCH installing displayport margins %s on scrollId=%" PRIu64 "\n",
+           ToString(aDisplayPortMargins).c_str(), viewID));
+    }
+  }
+  DisplayPortUtils::SetDisplayPortMargins(aContent, aPresShell,
+                                          aDisplayPortMargins, 0);
+  if (!hadDisplayPort) {
+    DisplayPortUtils::SetZeroMarginDisplayPortOnAsyncScrollableAncestors(
+        aContent->GetPrimaryFrame());
+  }
+
+  nsRect base(0, 0, aDisplayPortBase.width * AppUnitsPerCSSPixel(),
+              aDisplayPortBase.height * AppUnitsPerCSSPixel());
+  DisplayPortUtils::SetDisplayPortBaseIfNotSet(aContent, base);
+}
+
+static void SetPaintRequestTime(nsIContent* aContent,
+                                const TimeStamp& aPaintRequestTime) {
+  aContent->SetProperty(nsGkAtoms::paintRequestTime,
+                        new TimeStamp(aPaintRequestTime),
+                        nsINode::DeleteProperty<TimeStamp>);
+}
+
+void APZCCallbackHelper::NotifyLayerTransforms(
+    const nsTArray<MatrixMessage>& aTransforms) {
+  MOZ_ASSERT(NS_IsMainThread());
+  for (const MatrixMessage& msg : aTransforms) {
+    BrowserParent* parent =
+        BrowserParent::GetBrowserParentFromLayersId(msg.GetLayersId());
+    if (parent) {
+      parent->SetChildToParentConversionMatrix(
+          ViewAs<LayoutDeviceToLayoutDeviceMatrix4x4>(
+              msg.GetMatrix(),
+              PixelCastJustification::ContentProcessIsLayerInUiProcess),
+          msg.GetTopLevelViewportVisibleRectInBrowserCoords());
+    }
+  }
+}
+
+void APZCCallbackHelper::UpdateRootFrame(const RepaintRequest& aRequest) {
+  if (aRequest.GetScrollId() == ScrollableLayerGuid::NULL_SCROLL_ID) {
+    return;
+  }
+  RefPtr<nsIContent> content =
+      nsLayoutUtils::FindContentFor(aRequest.GetScrollId());
+  if (!content) {
+    return;
+  }
+
+  RefPtr<PresShell> presShell = GetPresShell(content);
+  if (!presShell || aRequest.GetPresShellId() != presShell->GetPresShellId()) {
+    return;
+  }
+
+  APZCCH_LOG("Handling request %s\n", ToString(aRequest).c_str());
+  if (nsLayoutUtils::AllowZoomingForDocument(presShell->GetDocument()) &&
+      aRequest.GetAsyncZoom().scale != 1.0) {
+    // If zooming is disabled then we don't really want to let APZ fiddle
+    // with these things. In theory setting the resolution here should be a
+    // no-op, but setting the visual viewport size is bad because it can cause a
+    // stale value to be returned by window.innerWidth/innerHeight (see bug
+    // 1187792).
+
+    float presShellResolution = presShell->GetResolution();
+
+    // If the pres shell resolution has changed on the content side side
+    // the time this repaint request was fired, consider this request out of
+    // date and drop it; setting a zoom based on the out-of-date resolution can
+    // have the effect of getting us stuck with the stale resolution.
+    if (!FuzzyEqualsMultiplicative(presShellResolution,
+                                   aRequest.GetPresShellResolution())) {
+      return;
+    }
+
+    // The pres shell resolution is updated by the the async zoom since the
+    // last paint.
+    presShellResolution =
+        aRequest.GetPresShellResolution() * aRequest.GetAsyncZoom().scale;
+    presShell->SetResolutionAndScaleTo(presShellResolution,
+                                       ResolutionChangeOrigin::Apz);
+
+    // Changing the resolution will trigger a reflow which will cause the
+    // main-thread scroll position to be realigned in layer pixels. This
+    // (subpixel) scroll mutation can trigger a scroll update to APZ which
+    // is undesirable. Instead of having that happen as part of the post-reflow
+    // code, we force it to happen here with ScrollOrigin::Apz so that it
+    // doesn't trigger a scroll update to APZ.
+    nsIScrollableFrame* sf =
+        nsLayoutUtils::FindScrollableFrameFor(aRequest.GetScrollId());
+    CSSPoint currentScrollPosition =
+        CSSPoint::FromAppUnits(sf->GetScrollPosition());
+    sf->ScrollToCSSPixelsApproximate(currentScrollPosition, ScrollOrigin::Apz);
+  }
+
+  // Do this as late as possible since scrolling can flush layout. It also
+  // adjusts the display port margins, so do it before we set those.
+  DisplayPortMargins displayPortMargins = ScrollFrame(content, aRequest);
+
+  SetDisplayPortMargins(presShell, content, displayPortMargins,
+                        aRequest.CalculateCompositedSizeInCssPixels());
+  SetPaintRequestTime(content, aRequest.GetPaintRequestTime());
+}
+
+void APZCCallbackHelper::UpdateSubFrame(const RepaintRequest& aRequest) {
+  if (aRequest.GetScrollId() == ScrollableLayerGuid::NULL_SCROLL_ID) {
+    return;
+  }
+  RefPtr<nsIContent> content =
+      nsLayoutUtils::FindContentFor(aRequest.GetScrollId());
+  if (!content) {
+    return;
+  }
+
+  // We don't currently support zooming for subframes, so nothing extra
+  // needs to be done beyond the tasks common to this and UpdateRootFrame.
+  DisplayPortMargins displayPortMargins = ScrollFrame(content, aRequest);
+  if (RefPtr<PresShell> presShell = GetPresShell(content)) {
+    SetDisplayPortMargins(presShell, content, displayPortMargins,
+                          aRequest.CalculateCompositedSizeInCssPixels());
+  }
+  SetPaintRequestTime(content, aRequest.GetPaintRequestTime());
+}
+
+bool APZCCallbackHelper::GetOrCreateScrollIdentifiers(
+    nsIContent* aContent, uint32_t* aPresShellIdOut,
+    ScrollableLayerGuid::ViewID* aViewIdOut) {
+  if (!aContent) {
+    return false;
+  }
+  *aViewIdOut = nsLayoutUtils::FindOrCreateIDFor(aContent);
+  if (PresShell* presShell = GetPresShell(aContent)) {
+    *aPresShellIdOut = presShell->GetPresShellId();
+    return true;
+  }
+  return false;
+}
+
+void APZCCallbackHelper::InitializeRootDisplayport(PresShell* aPresShell) {
+  // Create a view-id and set a zero-margin displayport for the root element
+  // of the root document in the chrome process. This ensures that the scroll
+  // frame for this element gets an APZC, which in turn ensures that all content
+  // in the chrome processes is covered by an APZC.
+  // The displayport is zero-margin because this element is generally not
+  // actually scrollable (if it is, APZC will set proper margins when it's
+  // scrolled).
+  if (!aPresShell) {
+    return;
+  }
+
+  MOZ_ASSERT(aPresShell->GetDocument());
+  nsIContent* content = aPresShell->GetDocument()->GetDocumentElement();
+  if (!content) {
+    return;
+  }
+
+  uint32_t presShellId;
+  ScrollableLayerGuid::ViewID viewId;
+  if (APZCCallbackHelper::GetOrCreateScrollIdentifiers(content, &presShellId,
+                                                       &viewId)) {
+    nsPresContext* pc = aPresShell->GetPresContext();
+    // This code is only correct for root content or toplevel documents.
+    MOZ_ASSERT(!pc || pc->IsRootContentDocumentCrossProcess() ||
+               !pc->GetParentPresContext());
+    nsIFrame* frame = aPresShell->GetRootScrollFrame();
+    if (!frame) {
+      frame = aPresShell->GetRootFrame();
+    }
+    nsRect baseRect;
+    if (frame) {
+      baseRect = nsRect(nsPoint(0, 0),
+                        nsLayoutUtils::CalculateCompositionSizeForFrame(frame));
+    } else if (pc) {
+      baseRect = nsRect(nsPoint(0, 0), pc->GetVisibleArea().Size());
+    }
+    MOZ_LOG(
+        sDisplayportLog, LogLevel::Debug,
+        ("Initializing root displayport on scrollId=%" PRIu64 "\n", viewId));
+    DisplayPortUtils::SetDisplayPortBaseIfNotSet(content, baseRect);
+    // Note that we also set the base rect that goes with these margins in
+    // nsRootBoxFrame::BuildDisplayList.
+    DisplayPortUtils::SetDisplayPortMargins(
+        content, aPresShell, DisplayPortMargins::Empty(content), 0);
+    DisplayPortUtils::SetZeroMarginDisplayPortOnAsyncScrollableAncestors(
+        content->GetPrimaryFrame());
+  }
+}
+
+nsPresContext* APZCCallbackHelper::GetPresContextForContent(
+    nsIContent* aContent) {
+  dom::Document* doc = aContent->GetComposedDoc();
+  if (!doc) {
+    return nullptr;
+  }
+  PresShell* presShell = doc->GetPresShell();
+  if (!presShell) {
+    return nullptr;
+  }
+  return presShell->GetPresContext();
+}
+
+PresShell* APZCCallbackHelper::GetRootContentDocumentPresShellForContent(
+    nsIContent* aContent) {
+  nsPresContext* context = GetPresContextForContent(aContent);
+  if (!context) {
+    return nullptr;
+  }
+  context = context->GetInProcessRootContentDocumentPresContext();
+  if (!context) {
+    return nullptr;
+  }
+  return context->PresShell();
+}
+
+nsEventStatus APZCCallbackHelper::DispatchWidgetEvent(WidgetGUIEvent& aEvent) {
+  nsEventStatus status = nsEventStatus_eConsumeNoDefault;
+  if (aEvent.mWidget) {
+    aEvent.mWidget->DispatchEvent(&aEvent, status);
+  }
+  return status;
+}
+
+nsEventStatus APZCCallbackHelper::DispatchSynthesizedMouseEvent(
+    EventMessage aMsg, uint64_t aTime, const LayoutDevicePoint& aRefPoint,
+    Modifiers aModifiers, int32_t aClickCount, nsIWidget* aWidget) {
+  MOZ_ASSERT(aMsg == eMouseMove || aMsg == eMouseDown || aMsg == eMouseUp ||
+             aMsg == eMouseLongTap);
+
+  WidgetMouseEvent event(true, aMsg, aWidget, WidgetMouseEvent::eReal,
+                         WidgetMouseEvent::eNormal);
+  event.mRefPoint = LayoutDeviceIntPoint::Truncate(aRefPoint.x, aRefPoint.y);
+  event.mTime = aTime;
+  event.mButton = MouseButton::ePrimary;
+  event.mInputSource = dom::MouseEvent_Binding::MOZ_SOURCE_TOUCH;
+  if (aMsg == eMouseLongTap) {
+    event.mFlags.mOnlyChromeDispatch = true;
+  }
+  if (aMsg != eMouseMove) {
+    event.mClickCount = aClickCount;
+  }
+  event.mModifiers = aModifiers;
+  // Real touch events will generate corresponding pointer events. We set
+  // convertToPointer to false to prevent the synthesized mouse events generate
+  // pointer events again.
+  event.convertToPointer = false;
+  return DispatchWidgetEvent(event);
+}
+
+bool APZCCallbackHelper::DispatchMouseEvent(
+    PresShell* aPresShell, const nsString& aType, const CSSPoint& aPoint,
+    int32_t aButton, int32_t aClickCount, int32_t aModifiers,
+    unsigned short aInputSourceArg, uint32_t aPointerId) {
+  NS_ENSURE_TRUE(aPresShell, true);
+
+  bool defaultPrevented = false;
+  nsContentUtils::SendMouseEvent(
+      aPresShell, aType, aPoint.x, aPoint.y, aButton,
+      nsIDOMWindowUtils::MOUSE_BUTTONS_NOT_SPECIFIED, aClickCount, aModifiers,
+      /* aIgnoreRootScrollFrame = */ false, 0, aInputSourceArg, aPointerId,
+      false, &defaultPrevented, false, /* aIsWidgetEventSynthesized = */ false);
+  return defaultPrevented;
+}
+
+void APZCCallbackHelper::FireSingleTapEvent(const LayoutDevicePoint& aPoint,
+                                            Modifiers aModifiers,
+                                            int32_t aClickCount,
+                                            nsIWidget* aWidget) {
+  if (aWidget->Destroyed()) {
+    return;
+  }
+  APZCCH_LOG("Dispatching single-tap component events to %s\n",
+             ToString(aPoint).c_str());
+  int time = 0;
+  DispatchSynthesizedMouseEvent(eMouseMove, time, aPoint, aModifiers,
+                                aClickCount, aWidget);
+  DispatchSynthesizedMouseEvent(eMouseDown, time, aPoint, aModifiers,
+                                aClickCount, aWidget);
+  DispatchSynthesizedMouseEvent(eMouseUp, time, aPoint, aModifiers, aClickCount,
+                                aWidget);
+}
+
+static dom::Element* GetDisplayportElementFor(
+    nsIScrollableFrame* aScrollableFrame) {
+  if (!aScrollableFrame) {
+    return nullptr;
+  }
+  nsIFrame* scrolledFrame = aScrollableFrame->GetScrolledFrame();
+  if (!scrolledFrame) {
+    return nullptr;
+  }
+  // |scrolledFrame| should at this point be the root content frame of the
+  // nearest ancestor scrollable frame. The element corresponding to this
+  // frame should be the one with the displayport set on it, so find that
+  // element and return it.
+  nsIContent* content = scrolledFrame->GetContent();
+  MOZ_ASSERT(content->IsElement());  // roc says this must be true
+  return content->AsElement();
+}
+
+static dom::Element* GetRootDocumentElementFor(nsIWidget* aWidget) {
+  // This returns the root element that ChromeProcessController sets the
+  // displayport on during initialization.
+  if (nsView* view = nsView::GetViewFor(aWidget)) {
+    if (PresShell* presShell = view->GetPresShell()) {
+      MOZ_ASSERT(presShell->GetDocument());
+      return presShell->GetDocument()->GetDocumentElement();
+    }
+  }
+  return nullptr;
+}
+
+namespace {
+
+using FrameForPointOption = nsLayoutUtils::FrameForPointOption;
+
+// Determine the scrollable target frame for the given point and add it to
+// the target list. If the frame doesn't have a displayport, set one.
+// Return whether or not the frame had a displayport that has already been
+// painted (in this case, the caller can send the SetTargetAPZC notification
+// right away, rather than waiting for a transaction to propagate the
+// displayport to APZ first).
+static bool PrepareForSetTargetAPZCNotification(
+    nsIWidget* aWidget, const LayersId& aLayersId, nsIFrame* aRootFrame,
+    const LayoutDeviceIntPoint& aRefPoint,
+    nsTArray<ScrollableLayerGuid>* aTargets) {
+  ScrollableLayerGuid guid(aLayersId, 0, ScrollableLayerGuid::NULL_SCROLL_ID);
+  RelativeTo relativeTo{aRootFrame, ViewportType::Visual};
+  nsPoint point = nsLayoutUtils::GetEventCoordinatesRelativeTo(
+      aWidget, aRefPoint, relativeTo);
+  nsIFrame* target = nsLayoutUtils::GetFrameForPoint(relativeTo, point);
+  nsIScrollableFrame* scrollAncestor =
+      target ? nsLayoutUtils::GetAsyncScrollableAncestorFrame(target)
+             : aRootFrame->PresShell()->GetRootScrollFrameAsScrollable();
+
+  // Assuming that if there's no scrollAncestor, there's already a displayPort.
+  nsCOMPtr<dom::Element> dpElement =
+      scrollAncestor ? GetDisplayportElementFor(scrollAncestor)
+                     : GetRootDocumentElementFor(aWidget);
+
+  if (MOZ_LOG_TEST(sApzHlpLog, LogLevel::Debug)) {
+    nsAutoString dpElementDesc;
+    if (dpElement) {
+      dpElement->Describe(dpElementDesc);
+    }
+    APZCCH_LOG("For event at %s found scrollable element %p (%s)\n",
+               ToString(aRefPoint).c_str(), dpElement.get(),
+               NS_LossyConvertUTF16toASCII(dpElementDesc).get());
+  }
+
+  bool guidIsValid = APZCCallbackHelper::GetOrCreateScrollIdentifiers(
+      dpElement, &(guid.mPresShellId), &(guid.mScrollId));
+  aTargets->AppendElement(guid);
+
+  if (!guidIsValid) {
+    return false;
+  }
+  if (DisplayPortUtils::HasDisplayPort(dpElement)) {
+    // If the element has a displayport but it hasn't been painted yet,
+    // we want the caller to wait for the paint to happen, but we don't
+    // need to set the displayport here since it's already been set.
+    return !DisplayPortUtils::HasPaintedDisplayPort(dpElement);
+  }
+
+  if (!scrollAncestor) {
+    // This can happen if the document element gets swapped out after
+    // ChromeProcessController runs InitializeRootDisplayport. In this case
+    // let's try to set a displayport again and bail out on this operation.
+    APZCCH_LOG("Widget %p's document element %p didn't have a displayport\n",
+               aWidget, dpElement.get());
+    APZCCallbackHelper::InitializeRootDisplayport(aRootFrame->PresShell());
+    return false;
+  }
+
+  APZCCH_LOG("%p didn't have a displayport, so setting one...\n",
+             dpElement.get());
+  MOZ_LOG(sDisplayportLog, LogLevel::Debug,
+          ("Activating displayport on scrollId=%" PRIu64 " for SetTargetAPZC\n",
+           guid.mScrollId));
+  bool activated = DisplayPortUtils::CalculateAndSetDisplayPortMargins(
+      scrollAncestor, DisplayPortUtils::RepaintMode::Repaint);
+  if (!activated) {
+    return false;
+  }
+
+  nsIFrame* frame = do_QueryFrame(scrollAncestor);
+  DisplayPortUtils::SetZeroMarginDisplayPortOnAsyncScrollableAncestors(frame);
+
+  return true;
+}
+
+static void SendLayersDependentApzcTargetConfirmation(
+    PresShell* aPresShell, uint64_t aInputBlockId,
+    nsTArray<ScrollableLayerGuid>&& aTargets) {
+  LayerManager* lm = aPresShell->GetLayerManager();
+  if (!lm) {
+    return;
+  }
+
+  if (WebRenderLayerManager* wrlm = lm->AsWebRenderLayerManager()) {
+    if (WebRenderBridgeChild* wrbc = wrlm->WrBridge()) {
+      wrbc->SendSetConfirmedTargetAPZC(aInputBlockId, aTargets);
+    }
+    return;
+  }
+
+  ShadowLayerForwarder* lf = lm->AsShadowForwarder();
+  if (!lf) {
+    return;
+  }
+
+  LayerTransactionChild* shadow = lf->GetShadowManager();
+  if (!shadow) {
+    return;
+  }
+
+  shadow->SendSetConfirmedTargetAPZC(aInputBlockId, aTargets);
+}
+
+}  // namespace
+
+DisplayportSetListener::DisplayportSetListener(
+    nsIWidget* aWidget, PresShell* aPresShell, const uint64_t& aInputBlockId,
+    nsTArray<ScrollableLayerGuid>&& aTargets)
+    : OneShotPostRefreshObserver(aPresShell),
+      mWidget(aWidget),
+      mInputBlockId(aInputBlockId),
+      mTargets(std::move(aTargets)) {
+  MOZ_ASSERT(!mAction, "Setting Action twice");
+  mAction = [](PresShell* aPresShell,
+               OneShotPostRefreshObserver* aThisObserver) {
+    OnPostRefresh(static_cast<DisplayportSetListener*>(aThisObserver),
+                  aPresShell);
+  };
+}
+
+DisplayportSetListener::~DisplayportSetListener() = default;
+
+bool DisplayportSetListener::Register() {
+  if (nsPresContext* presContext = mPresShell->GetPresContext()) {
+    presContext->RegisterOneShotPostRefreshObserver(this);
+    APZCCH_LOG("Successfully registered post-refresh observer\n");
+    return true;
+  }
+  // In case of failure just send the notification right away
+  APZCCH_LOG("Sending target APZCs for input block %" PRIu64 "\n",
+             mInputBlockId);
+  mWidget->SetConfirmedTargetAPZC(mInputBlockId, mTargets);
+  return false;
+}
+
+/* static */
+void DisplayportSetListener::OnPostRefresh(DisplayportSetListener* aListener,
+                                           PresShell* aPresShell) {
+  APZCCH_LOG("Got refresh, sending target APZCs for input block %" PRIu64 "\n",
+             aListener->mInputBlockId);
+  SendLayersDependentApzcTargetConfirmation(
+      aPresShell, aListener->mInputBlockId, std::move(aListener->mTargets));
+}
+
+UniquePtr<DisplayportSetListener>
+APZCCallbackHelper::SendSetTargetAPZCNotification(nsIWidget* aWidget,
+                                                  dom::Document* aDocument,
+                                                  const WidgetGUIEvent& aEvent,
+                                                  const LayersId& aLayersId,
+                                                  uint64_t aInputBlockId) {
+  if (!aWidget || !aDocument) {
+    return nullptr;
+  }
+  if (aInputBlockId == sLastTargetAPZCNotificationInputBlock) {
+    // We have already confirmed the target APZC for a previous event of this
+    // input block. If we activated a scroll frame for this input block,
+    // sending another target APZC confirmation would be harmful, as it might
+    // race the original confirmation (which needs to go through a layers
+    // transaction).
+    APZCCH_LOG("Not resending target APZC confirmation for input block %" PRIu64
+               "\n",
+               aInputBlockId);
+    return nullptr;
+  }
+  sLastTargetAPZCNotificationInputBlock = aInputBlockId;
+  if (PresShell* presShell = aDocument->GetPresShell()) {
+    if (nsIFrame* rootFrame = presShell->GetRootFrame()) {
+      bool waitForRefresh = false;
+      nsTArray<ScrollableLayerGuid> targets;
+
+      if (const WidgetTouchEvent* touchEvent = aEvent.AsTouchEvent()) {
+        for (size_t i = 0; i < touchEvent->mTouches.Length(); i++) {
+          waitForRefresh |= PrepareForSetTargetAPZCNotification(
+              aWidget, aLayersId, rootFrame, touchEvent->mTouches[i]->mRefPoint,
+              &targets);
+        }
+      } else if (const WidgetWheelEvent* wheelEvent = aEvent.AsWheelEvent()) {
+        waitForRefresh = PrepareForSetTargetAPZCNotification(
+            aWidget, aLayersId, rootFrame, wheelEvent->mRefPoint, &targets);
+      } else if (const WidgetMouseEvent* mouseEvent = aEvent.AsMouseEvent()) {
+        waitForRefresh = PrepareForSetTargetAPZCNotification(
+            aWidget, aLayersId, rootFrame, mouseEvent->mRefPoint, &targets);
+      }
+      // TODO: Do other types of events need to be handled?
+
+      if (!targets.IsEmpty()) {
+        if (waitForRefresh) {
+          APZCCH_LOG(
+              "At least one target got a new displayport, need to wait for "
+              "refresh\n");
+          return MakeUnique<DisplayportSetListener>(
+              aWidget, presShell, aInputBlockId, std::move(targets));
+        }
+        APZCCH_LOG("Sending target APZCs for input block %" PRIu64 "\n",
+                   aInputBlockId);
+        aWidget->SetConfirmedTargetAPZC(aInputBlockId, targets);
+      }
+    }
+  }
+  return nullptr;
+}
+
+nsTArray<TouchBehaviorFlags>
+APZCCallbackHelper::SendSetAllowedTouchBehaviorNotification(
+    nsIWidget* aWidget, dom::Document* aDocument,
+    const WidgetTouchEvent& aEvent, uint64_t aInputBlockId,
+    const SetAllowedTouchBehaviorCallback& aCallback) {
+  nsTArray<TouchBehaviorFlags> flags;
+  if (!aWidget || !aDocument) {
+    return flags;
+  }
+  if (PresShell* presShell = aDocument->GetPresShell()) {
+    if (nsIFrame* rootFrame = presShell->GetRootFrame()) {
+      for (uint32_t i = 0; i < aEvent.mTouches.Length(); i++) {
+        flags.AppendElement(TouchActionHelper::GetAllowedTouchBehavior(
+            aWidget, RelativeTo{rootFrame, ViewportType::Visual},
+            aEvent.mTouches[i]->mRefPoint));
+      }
+      aCallback(aInputBlockId, flags);
+    }
+  }
+  return flags;
+}
+
+void APZCCallbackHelper::NotifyMozMouseScrollEvent(
+    const ScrollableLayerGuid::ViewID& aScrollId, const nsString& aEvent) {
+  nsCOMPtr<nsIContent> targetContent = nsLayoutUtils::FindContentFor(aScrollId);
+  if (!targetContent) {
+    return;
+  }
+  RefPtr<dom::Document> ownerDoc = targetContent->OwnerDoc();
+  if (!ownerDoc) {
+    return;
+  }
+
+  nsContentUtils::DispatchEventOnlyToChrome(ownerDoc, targetContent, aEvent,
+                                            CanBubble::eYes, Cancelable::eYes);
+}
+
+void APZCCallbackHelper::NotifyFlushComplete(PresShell* aPresShell) {
+  MOZ_ASSERT(NS_IsMainThread());
+  // In some cases, flushing the APZ state to the main thread doesn't actually
+  // trigger a flush and repaint (this is an intentional optimization - the
+  // stuff visible to the user is still correct). However, reftests update their
+  // snapshot based on invalidation events that are emitted during paints,
+  // so we ensure that we kick off a paint when an APZ flush is done. Note that
+  // only chrome/testing code can trigger this behaviour.
+  if (aPresShell && aPresShell->GetRootFrame()) {
+    aPresShell->GetRootFrame()->SchedulePaint(nsIFrame::PAINT_DEFAULT, false);
+  }
+
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  MOZ_ASSERT(observerService);
+  observerService->NotifyObservers(nullptr, "apz-repaints-flushed", nullptr);
+}
+
+/* static */
+bool APZCCallbackHelper::IsScrollInProgress(nsIScrollableFrame* aFrame) {
+  using IncludeApzAnimation = nsIScrollableFrame::IncludeApzAnimation;
+
+  return aFrame->IsScrollAnimating(IncludeApzAnimation::No) ||
+         nsLayoutUtils::CanScrollOriginClobberApz(aFrame->LastScrollOrigin());
+}
+
+/* static */
+void APZCCallbackHelper::NotifyAsyncScrollbarDragInitiated(
+    uint64_t aDragBlockId, const ScrollableLayerGuid::ViewID& aScrollId,
+    ScrollDirection aDirection) {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (nsIScrollableFrame* scrollFrame =
+          nsLayoutUtils::FindScrollableFrameFor(aScrollId)) {
+    scrollFrame->AsyncScrollbarDragInitiated(aDragBlockId, aDirection);
+  }
+}
+
+/* static */
+void APZCCallbackHelper::NotifyAsyncScrollbarDragRejected(
+    const ScrollableLayerGuid::ViewID& aScrollId) {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (nsIScrollableFrame* scrollFrame =
+          nsLayoutUtils::FindScrollableFrameFor(aScrollId)) {
+    scrollFrame->AsyncScrollbarDragRejected();
+  }
+}
+
+/* static */
+void APZCCallbackHelper::NotifyAsyncAutoscrollRejected(
+    const ScrollableLayerGuid::ViewID& aScrollId) {
+  MOZ_ASSERT(NS_IsMainThread());
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  MOZ_ASSERT(observerService);
+
+  nsAutoString data;
+  data.AppendInt(aScrollId);
+  observerService->NotifyObservers(nullptr, "autoscroll-rejected-by-apz",
+                                   data.get());
+}
+
+/* static */
+void APZCCallbackHelper::CancelAutoscroll(
+    const ScrollableLayerGuid::ViewID& aScrollId) {
+  MOZ_ASSERT(NS_IsMainThread());
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  MOZ_ASSERT(observerService);
+
+  nsAutoString data;
+  data.AppendInt(aScrollId);
+  observerService->NotifyObservers(nullptr, "apz:cancel-autoscroll",
+                                   data.get());
+}
+
+/* static */
+void APZCCallbackHelper::NotifyPinchGesture(
+    PinchGestureInput::PinchGestureType aType,
+    const LayoutDevicePoint& aFocusPoint, LayoutDeviceCoord aSpanChange,
+    Modifiers aModifiers, const nsCOMPtr<nsIWidget>& aWidget) {
+  APZCCH_LOG("APZCCallbackHelper dispatching pinch gesture\n");
+  EventMessage msg;
+  switch (aType) {
+    case PinchGestureInput::PINCHGESTURE_START:
+      msg = eMagnifyGestureStart;
+      break;
+    case PinchGestureInput::PINCHGESTURE_SCALE:
+      msg = eMagnifyGestureUpdate;
+      break;
+    case PinchGestureInput::PINCHGESTURE_FINGERLIFTED:
+    case PinchGestureInput::PINCHGESTURE_END:
+      msg = eMagnifyGesture;
+      break;
+  }
+
+  WidgetSimpleGestureEvent event(true, msg, aWidget.get());
+  // XXX mDelta for the eMagnifyGesture event is supposed to be the
+  // cumulative magnification over the entire gesture (per docs in
+  // SimpleGestureEvent.webidl) but currently APZ just sends us a zero
+  // aSpanChange for that event, so the mDelta is wrong. Nothing relies
+  // on that currently, but we might want to fix it at some point.
+  event.mDelta = aSpanChange;
+  event.mModifiers = aModifiers;
+  event.mRefPoint = RoundedToInt(aFocusPoint);
+
+  DispatchWidgetEvent(event);
+}
+
+}  // namespace layers
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/APZCCallbackHelper.h b/gfx/layers/apz/util/APZCCallbackHelper.h
new file mode 100644
index 0000000000..4bf6806c76
--- /dev/null
+++ b/gfx/layers/apz/util/APZCCallbackHelper.h
@@ -0,0 +1,204 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 mozilla_layers_APZCCallbackHelper_h
+#define mozilla_layers_APZCCallbackHelper_h
+
+#include "InputData.h"
+#include "LayersTypes.h"
+#include "Units.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/layers/MatrixMessage.h"
+#include "nsRefreshObservers.h"
+
+#include <functional>
+
+class nsIContent;
+class nsIScrollableFrame;
+class nsIWidget;
+template <class T>
+struct already_AddRefed;
+template <class T>
+class nsCOMPtr;
+
+namespace mozilla {
+
+class PresShell;
+
+namespace layers {
+
+struct RepaintRequest;
+
+typedef std::function<void(uint64_t, const nsTArray<TouchBehaviorFlags>&)>
+    SetAllowedTouchBehaviorCallback;
+
+/* Refer to documentation on SendSetTargetAPZCNotification for this class */
+class DisplayportSetListener : public OneShotPostRefreshObserver {
+ public:
+  DisplayportSetListener(nsIWidget* aWidget, PresShell* aPresShell,
+                         const uint64_t& aInputBlockId,
+                         nsTArray<ScrollableLayerGuid>&& aTargets);
+  virtual ~DisplayportSetListener();
+  bool Register();
+
+ private:
+  RefPtr<nsIWidget> mWidget;
+  uint64_t mInputBlockId;
+  nsTArray<ScrollableLayerGuid> mTargets;
+
+  static void OnPostRefresh(DisplayportSetListener* aListener,
+                            PresShell* aPresShell);
+};
+
+/* This class contains some helper methods that facilitate implementing the
+   GeckoContentController callback interface required by the
+   AsyncPanZoomController. Since different platforms need to implement this
+   interface in similar-but- not-quite-the-same ways, this utility class
+   provides some helpful methods to hold code that can be shared across the
+   different platform implementations.
+ */
+class APZCCallbackHelper {
+  typedef mozilla::layers::ScrollableLayerGuid ScrollableLayerGuid;
+
+ public:
+  static void NotifyLayerTransforms(const nsTArray<MatrixMessage>& aTransforms);
+
+  /* Applies the scroll and zoom parameters from the given RepaintRequest object
+     to the root frame for the given metrics' scrollId. If tiled thebes layers
+     are enabled, this will align the displayport to tile boundaries. Setting
+     the scroll position can cause some small adjustments to be made to the
+     actual scroll position. */
+  static void UpdateRootFrame(const RepaintRequest& aRequest);
+
+  /* Applies the scroll parameters from the given RepaintRequest object to the
+     subframe corresponding to given metrics' scrollId. If tiled thebes
+     layers are enabled, this will align the displayport to tile boundaries.
+     Setting the scroll position can cause some small adjustments to be made
+     to the actual scroll position. */
+  static void UpdateSubFrame(const RepaintRequest& aRequest);
+
+  /* Get the presShellId and view ID for the given content element.
+   * If the view ID does not exist, one is created.
+   * The pres shell ID should generally already exist; if it doesn't for some
+   * reason, false is returned. */
+  static bool GetOrCreateScrollIdentifiers(
+      nsIContent* aContent, uint32_t* aPresShellIdOut,
+      ScrollableLayerGuid::ViewID* aViewIdOut);
+
+  /* Initialize a zero-margin displayport on the root document element of the
+     given presShell. */
+  static void InitializeRootDisplayport(PresShell* aPresShell);
+
+  /* Get the pres context associated with the document enclosing |aContent|. */
+  static nsPresContext* GetPresContextForContent(nsIContent* aContent);
+
+  /* Get the pres shell associated with the root content document enclosing
+   * |aContent|. */
+  static PresShell* GetRootContentDocumentPresShellForContent(
+      nsIContent* aContent);
+
+  /* Dispatch a widget event via the widget stored in the event, if any.
+   * In a child process, allows the BrowserParent event-capture mechanism to
+   * intercept the event. */
+  static nsEventStatus DispatchWidgetEvent(WidgetGUIEvent& aEvent);
+
+  /* Synthesize a mouse event with the given parameters, and dispatch it
+   * via the given widget. */
+  static nsEventStatus DispatchSynthesizedMouseEvent(
+      EventMessage aMsg, uint64_t aTime, const LayoutDevicePoint& aRefPoint,
+      Modifiers aModifiers, int32_t aClickCount, nsIWidget* aWidget);
+
+  /* Dispatch a mouse event with the given parameters.
+   * Return whether or not any listeners have called preventDefault on the
+   * event.
+   * This is a lightweight wrapper around nsContentUtils::SendMouseEvent()
+   * and as such expects |aPoint| to be in layout coordinates. */
+  MOZ_CAN_RUN_SCRIPT
+  static bool DispatchMouseEvent(PresShell* aPresShell, const nsString& aType,
+                                 const CSSPoint& aPoint, int32_t aButton,
+                                 int32_t aClickCount, int32_t aModifiers,
+                                 unsigned short aInputSourceArg,
+                                 uint32_t aPointerId);
+
+  /* Fire a single-tap event at the given point. The event is dispatched
+   * via the given widget. */
+  static void FireSingleTapEvent(const LayoutDevicePoint& aPoint,
+                                 Modifiers aModifiers, int32_t aClickCount,
+                                 nsIWidget* aWidget);
+
+  /* Perform hit-testing on the touch points of |aEvent| to determine
+   * which scrollable frames they target. If any of these frames don't have
+   * a displayport, set one.
+   *
+   * If any displayports need to be set, this function returns a heap-allocated
+   * object. The caller is responsible for calling Register() on that object,
+   * and release()'ing the UniquePtr if that Register() call returns true.
+   * The object registers itself as a post-refresh observer on the presShell
+   * and ensures that notifications get sent to APZ correctly after the
+   * refresh.
+   *
+   * Having the caller manage this object is desirable in case they want to
+   * (a) know about the fact that a displayport needs to be set, and
+   * (b) register a post-refresh observer of their own that will run in
+   *     a defined ordering relative to the APZ messages.
+   */
+  static UniquePtr<DisplayportSetListener> SendSetTargetAPZCNotification(
+      nsIWidget* aWidget, mozilla::dom::Document* aDocument,
+      const WidgetGUIEvent& aEvent, const LayersId& aLayersId,
+      uint64_t aInputBlockId);
+
+  /* Figure out the allowed touch behaviors of each touch point in |aEvent|
+   * and send that information to the provided callback. Also returns the
+   * allowed touch behaviors. */
+  static nsTArray<TouchBehaviorFlags> SendSetAllowedTouchBehaviorNotification(
+      nsIWidget* aWidget, mozilla::dom::Document* aDocument,
+      const WidgetTouchEvent& aEvent, uint64_t aInputBlockId,
+      const SetAllowedTouchBehaviorCallback& aCallback);
+
+  /* Notify content of a mouse scroll testing event. */
+  static void NotifyMozMouseScrollEvent(
+      const ScrollableLayerGuid::ViewID& aScrollId, const nsString& aEvent);
+
+  /* Notify content that the repaint flush is complete. */
+  static void NotifyFlushComplete(PresShell* aPresShell);
+
+  static void NotifyAsyncScrollbarDragInitiated(
+      uint64_t aDragBlockId, const ScrollableLayerGuid::ViewID& aScrollId,
+      ScrollDirection aDirection);
+  static void NotifyAsyncScrollbarDragRejected(
+      const ScrollableLayerGuid::ViewID& aScrollId);
+  static void NotifyAsyncAutoscrollRejected(
+      const ScrollableLayerGuid::ViewID& aScrollId);
+
+  static void CancelAutoscroll(const ScrollableLayerGuid::ViewID& aScrollId);
+
+  /*
+   * Check if the scrollable frame is currently in the middle of a main thread
+   * async or smooth scroll, or has already requested some other apz scroll that
+   * hasn't been acknowledged by apz.
+   *
+   * We want to discard apz updates to the main-thread scroll offset if this is
+   * true to prevent clobbering higher priority origins.
+   */
+  static bool IsScrollInProgress(nsIScrollableFrame* aFrame);
+
+  /* Notify content of the progress of a pinch gesture that APZ won't do
+   * zooming for (because the apz.allow_zooming pref is false). This function
+   * will dispatch appropriate WidgetSimpleGestureEvent events to gecko.
+   */
+  static void NotifyPinchGesture(PinchGestureInput::PinchGestureType aType,
+                                 const LayoutDevicePoint& aFocusPoint,
+                                 LayoutDeviceCoord aSpanChange,
+                                 Modifiers aModifiers,
+                                 const nsCOMPtr<nsIWidget>& aWidget);
+
+ private:
+  static uint64_t sLastTargetAPZCNotificationInputBlock;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /* mozilla_layers_APZCCallbackHelper_h */
diff --git a/gfx/layers/apz/util/APZEventState.cpp b/gfx/layers/apz/util/APZEventState.cpp
new file mode 100644
index 0000000000..159952f772
--- /dev/null
+++ b/gfx/layers/apz/util/APZEventState.cpp
@@ -0,0 +1,553 @@
+/* -*- 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 "APZEventState.h"
+
+#include <utility>
+
+#include "APZCCallbackHelper.h"
+#include "ActiveElementManager.h"
+#include "TouchManager.h"
+#include "mozilla/BasicEvents.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/PositionedEventTargeting.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/StaticPrefs_ui.h"
+#include "mozilla/ToString.h"
+#include "mozilla/TouchEvents.h"
+#include "mozilla/ViewportUtils.h"
+#include "mozilla/dom/BrowserChild.h"
+#include "mozilla/dom/MouseEventBinding.h"
+#include "mozilla/layers/APZCCallbackHelper.h"
+#include "mozilla/layers/IAPZCTreeManager.h"
+#include "mozilla/widget/nsAutoRollup.h"
+#include "nsCOMPtr.h"
+#include "nsDocShell.h"
+#include "nsIDOMWindowUtils.h"
+#include "nsINamed.h"
+#include "nsIScrollableFrame.h"
+#include "nsIScrollbarMediator.h"
+#include "nsITimer.h"
+#include "nsIWeakReferenceUtils.h"
+#include "nsIWidget.h"
+#include "nsLayoutUtils.h"
+#include "nsQueryFrame.h"
+
+static mozilla::LazyLogModule sApzEvtLog("apz.eventstate");
+#define APZES_LOG(...) MOZ_LOG(sApzEvtLog, LogLevel::Debug, (__VA_ARGS__))
+
+// Static helper functions
+namespace {
+
+int32_t WidgetModifiersToDOMModifiers(mozilla::Modifiers aModifiers) {
+  int32_t result = 0;
+  if (aModifiers & mozilla::MODIFIER_SHIFT) {
+    result |= nsIDOMWindowUtils::MODIFIER_SHIFT;
+  }
+  if (aModifiers & mozilla::MODIFIER_CONTROL) {
+    result |= nsIDOMWindowUtils::MODIFIER_CONTROL;
+  }
+  if (aModifiers & mozilla::MODIFIER_ALT) {
+    result |= nsIDOMWindowUtils::MODIFIER_ALT;
+  }
+  if (aModifiers & mozilla::MODIFIER_META) {
+    result |= nsIDOMWindowUtils::MODIFIER_META;
+  }
+  if (aModifiers & mozilla::MODIFIER_ALTGRAPH) {
+    result |= nsIDOMWindowUtils::MODIFIER_ALTGRAPH;
+  }
+  if (aModifiers & mozilla::MODIFIER_CAPSLOCK) {
+    result |= nsIDOMWindowUtils::MODIFIER_CAPSLOCK;
+  }
+  if (aModifiers & mozilla::MODIFIER_FN) {
+    result |= nsIDOMWindowUtils::MODIFIER_FN;
+  }
+  if (aModifiers & mozilla::MODIFIER_FNLOCK) {
+    result |= nsIDOMWindowUtils::MODIFIER_FNLOCK;
+  }
+  if (aModifiers & mozilla::MODIFIER_NUMLOCK) {
+    result |= nsIDOMWindowUtils::MODIFIER_NUMLOCK;
+  }
+  if (aModifiers & mozilla::MODIFIER_SCROLLLOCK) {
+    result |= nsIDOMWindowUtils::MODIFIER_SCROLLLOCK;
+  }
+  if (aModifiers & mozilla::MODIFIER_SYMBOL) {
+    result |= nsIDOMWindowUtils::MODIFIER_SYMBOL;
+  }
+  if (aModifiers & mozilla::MODIFIER_SYMBOLLOCK) {
+    result |= nsIDOMWindowUtils::MODIFIER_SYMBOLLOCK;
+  }
+  if (aModifiers & mozilla::MODIFIER_OS) {
+    result |= nsIDOMWindowUtils::MODIFIER_OS;
+  }
+  return result;
+}
+
+}  // namespace
+
+namespace mozilla {
+namespace layers {
+
+APZEventState::APZEventState(nsIWidget* aWidget,
+                             ContentReceivedInputBlockCallback&& aCallback)
+    : mWidget(nullptr)  // initialized in constructor body
+      ,
+      mActiveElementManager(new ActiveElementManager()),
+      mContentReceivedInputBlockCallback(std::move(aCallback)),
+      mPendingTouchPreventedResponse(false),
+      mPendingTouchPreventedBlockId(0),
+      mEndTouchIsClick(false),
+      mFirstTouchCancelled(false),
+      mTouchEndCancelled(false),
+      mLastTouchIdentifier(0) {
+  nsresult rv;
+  mWidget = do_GetWeakReference(aWidget, &rv);
+  MOZ_ASSERT(NS_SUCCEEDED(rv),
+             "APZEventState constructed with a widget that"
+             " does not support weak references. APZ will NOT work!");
+}
+
+APZEventState::~APZEventState() = default;
+
+class DelayedFireSingleTapEvent final : public nsITimerCallback,
+                                        public nsINamed {
+ public:
+  NS_DECL_ISUPPORTS
+
+  DelayedFireSingleTapEvent(nsWeakPtr aWidget, LayoutDevicePoint& aPoint,
+                            Modifiers aModifiers, int32_t aClickCount,
+                            nsITimer* aTimer, RefPtr<nsIContent>& aTouchRollup)
+      : mWidget(aWidget),
+        mPoint(aPoint),
+        mModifiers(aModifiers),
+        mClickCount(aClickCount)
+        // Hold the reference count until we are called back.
+        ,
+        mTimer(aTimer),
+        mTouchRollup(aTouchRollup) {}
+
+  NS_IMETHOD Notify(nsITimer*) override {
+    if (nsCOMPtr<nsIWidget> widget = do_QueryReferent(mWidget)) {
+      widget::nsAutoRollup rollup(mTouchRollup.get());
+      APZCCallbackHelper::FireSingleTapEvent(mPoint, mModifiers, mClickCount,
+                                             widget);
+    }
+    mTimer = nullptr;
+    return NS_OK;
+  }
+
+  NS_IMETHOD
+  GetName(nsACString& aName) override {
+    aName.AssignLiteral("DelayedFireSingleTapEvent");
+    return NS_OK;
+  }
+
+  void ClearTimer() { mTimer = nullptr; }
+
+ private:
+  ~DelayedFireSingleTapEvent() = default;
+
+  nsWeakPtr mWidget;
+  LayoutDevicePoint mPoint;
+  Modifiers mModifiers;
+  int32_t mClickCount;
+  nsCOMPtr<nsITimer> mTimer;
+  RefPtr<nsIContent> mTouchRollup;
+};
+
+NS_IMPL_ISUPPORTS(DelayedFireSingleTapEvent, nsITimerCallback, nsINamed)
+
+void APZEventState::ProcessSingleTap(const CSSPoint& aPoint,
+                                     const CSSToLayoutDeviceScale& aScale,
+                                     Modifiers aModifiers,
+                                     int32_t aClickCount) {
+  APZES_LOG("Handling single tap at %s with %d\n", ToString(aPoint).c_str(),
+            mTouchEndCancelled);
+
+  RefPtr<nsIContent> touchRollup = GetTouchRollup();
+  mTouchRollup = nullptr;
+
+  nsCOMPtr<nsIWidget> widget = GetWidget();
+  if (!widget) {
+    return;
+  }
+
+  if (mTouchEndCancelled) {
+    return;
+  }
+
+  LayoutDevicePoint ldPoint = aPoint * aScale;
+
+  APZES_LOG("Scheduling timer for click event\n");
+  nsCOMPtr<nsITimer> timer = NS_NewTimer();
+  RefPtr<DelayedFireSingleTapEvent> callback = new DelayedFireSingleTapEvent(
+      mWidget, ldPoint, aModifiers, aClickCount, timer, touchRollup);
+  nsresult rv = timer->InitWithCallback(
+      callback, StaticPrefs::ui_touch_activation_duration_ms(),
+      nsITimer::TYPE_ONE_SHOT);
+  if (NS_FAILED(rv)) {
+    // Make |callback| not hold the timer, so they will both be destructed when
+    // we leave the scope of this function.
+    callback->ClearTimer();
+  }
+}
+
+bool APZEventState::FireContextmenuEvents(PresShell* aPresShell,
+                                          const CSSPoint& aPoint,
+                                          const CSSToLayoutDeviceScale& aScale,
+                                          Modifiers aModifiers,
+                                          const nsCOMPtr<nsIWidget>& aWidget) {
+  // Suppress retargeting for mouse events generated by a long-press
+  EventRetargetSuppression suppression;
+
+  // Synthesize mousemove event for allowing users to emulate to move mouse
+  // cursor over the element.  As a result, users can open submenu UI which
+  // is opened when mouse cursor is moved over a link (i.e., it's a case that
+  // users cannot stay in the page after tapping it).  So, this improves
+  // accessibility in websites which are designed for desktop.
+  // Note that we don't need to check whether mousemove event is consumed or
+  // not because Chrome also ignores the result.
+  APZCCallbackHelper::DispatchSynthesizedMouseEvent(
+      eMouseMove, 0 /* time */, aPoint * aScale, aModifiers, 0 /* clickCount */,
+      aWidget);
+
+  // Converting the modifiers to DOM format for the DispatchMouseEvent call
+  // is the most useless thing ever because nsDOMWindowUtils::SendMouseEvent
+  // just converts them back to widget format, but that API has many callers,
+  // including in JS code, so it's not trivial to change.
+  CSSPoint point = CSSPoint::FromAppUnits(
+      ViewportUtils::VisualToLayout(CSSPoint::ToAppUnits(aPoint), aPresShell));
+  bool eventHandled = APZCCallbackHelper::DispatchMouseEvent(
+      aPresShell, u"contextmenu"_ns, point, 2, 1,
+      WidgetModifiersToDOMModifiers(aModifiers),
+      dom::MouseEvent_Binding::MOZ_SOURCE_TOUCH,
+      0 /* Use the default value here. */);
+
+  APZES_LOG("Contextmenu event handled: %d\n", eventHandled);
+  if (eventHandled) {
+    // If the contextmenu event was handled then we're showing a contextmenu,
+    // and so we should remove any activation
+    mActiveElementManager->ClearActivation();
+#ifndef XP_WIN
+  } else {
+    // If the contextmenu wasn't consumed, fire the eMouseLongTap event.
+    nsEventStatus status = APZCCallbackHelper::DispatchSynthesizedMouseEvent(
+        eMouseLongTap, /*time*/ 0, aPoint * aScale, aModifiers,
+        /*clickCount*/ 1, aWidget);
+    eventHandled = (status == nsEventStatus_eConsumeNoDefault);
+    APZES_LOG("eMouseLongTap event handled: %d\n", eventHandled);
+#endif
+  }
+
+  return eventHandled;
+}
+
+void APZEventState::ProcessLongTap(PresShell* aPresShell,
+                                   const CSSPoint& aPoint,
+                                   const CSSToLayoutDeviceScale& aScale,
+                                   Modifiers aModifiers,
+                                   uint64_t aInputBlockId) {
+  APZES_LOG("Handling long tap at %s\n", ToString(aPoint).c_str());
+
+  nsCOMPtr<nsIWidget> widget = GetWidget();
+  if (!widget) {
+    return;
+  }
+
+  SendPendingTouchPreventedResponse(false);
+
+#ifdef XP_WIN
+  // On Windows, we fire the contextmenu events when the user lifts their
+  // finger, in keeping with the platform convention. This happens in the
+  // ProcessLongTapUp function. However, we still fire the eMouseLongTap event
+  // at this time, because things like text selection or dragging may want
+  // to know about it.
+  nsEventStatus status = APZCCallbackHelper::DispatchSynthesizedMouseEvent(
+      eMouseLongTap, /*time*/ 0, aPoint * aScale, aModifiers, /*clickCount*/ 1,
+      widget);
+
+  bool eventHandled = (status == nsEventStatus_eConsumeNoDefault);
+#else
+  bool eventHandled =
+      FireContextmenuEvents(aPresShell, aPoint, aScale, aModifiers, widget);
+#endif
+  mContentReceivedInputBlockCallback(aInputBlockId, eventHandled);
+
+  if (eventHandled) {
+    // Also send a touchcancel to content, so that listeners that might be
+    // waiting for a touchend don't trigger.
+    WidgetTouchEvent cancelTouchEvent(true, eTouchCancel, widget.get());
+    cancelTouchEvent.mModifiers = aModifiers;
+    auto ldPoint = LayoutDeviceIntPoint::Round(aPoint * aScale);
+    cancelTouchEvent.mTouches.AppendElement(new mozilla::dom::Touch(
+        mLastTouchIdentifier, ldPoint, LayoutDeviceIntPoint(), 0, 0));
+    APZCCallbackHelper::DispatchWidgetEvent(cancelTouchEvent);
+  }
+}
+
+void APZEventState::ProcessLongTapUp(PresShell* aPresShell,
+                                     const CSSPoint& aPoint,
+                                     const CSSToLayoutDeviceScale& aScale,
+                                     Modifiers aModifiers) {
+#ifdef XP_WIN
+  nsCOMPtr<nsIWidget> widget = GetWidget();
+  if (widget) {
+    FireContextmenuEvents(aPresShell, aPoint, aScale, aModifiers, widget);
+  }
+#endif
+}
+
+void APZEventState::ProcessTouchEvent(
+    const WidgetTouchEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    uint64_t aInputBlockId, nsEventStatus aApzResponse,
+    nsEventStatus aContentResponse,
+    nsTArray<TouchBehaviorFlags>&& aAllowedTouchBehaviors) {
+  if (aEvent.mMessage == eTouchStart && aEvent.mTouches.Length() > 0) {
+    mActiveElementManager->SetTargetElement(aEvent.mTouches[0]->GetTarget());
+    mLastTouchIdentifier = aEvent.mTouches[0]->Identifier();
+  }
+  if (aEvent.mMessage == eTouchStart) {
+    // We get the allowed touch behaviors on a touchstart, but may not actually
+    // use them until the first touchmove, so we stash them in a member
+    // variable.
+    mTouchBlockAllowedBehaviors = std::move(aAllowedTouchBehaviors);
+  }
+
+  bool isTouchPrevented = aContentResponse == nsEventStatus_eConsumeNoDefault;
+  bool sentContentResponse = false;
+  APZES_LOG("Handling event type %d isPrevented=%d\n", aEvent.mMessage,
+            isTouchPrevented);
+  switch (aEvent.mMessage) {
+    case eTouchStart: {
+      mTouchEndCancelled = false;
+      mTouchRollup = do_GetWeakReference(widget::nsAutoRollup::GetLastRollup());
+
+      SendPendingTouchPreventedResponse(false);
+      // The above call may have sent a message to APZ if we get two
+      // TOUCH_STARTs in a row and just responded to the first one.
+
+      // We're about to send a response back to APZ, but we should only do it
+      // for events that went through APZ (which should be all of them).
+      MOZ_ASSERT(aEvent.mFlags.mHandledByAPZ);
+
+      // If the first touchstart event was preventDefaulted, ensure that any
+      // subsequent additional touchstart events also get preventDefaulted. This
+      // ensures that e.g. pinch zooming is prevented even if just the first
+      // touchstart was prevented by content.
+      if (mTouchCounter.GetActiveTouchCount() == 0) {
+        mFirstTouchCancelled = isTouchPrevented;
+      } else {
+        if (mFirstTouchCancelled && !isTouchPrevented) {
+          APZES_LOG(
+              "Propagating prevent-default from first-touch for block %" PRIu64
+              "\n",
+              aInputBlockId);
+        }
+        isTouchPrevented |= mFirstTouchCancelled;
+      }
+
+      if (isTouchPrevented) {
+        mContentReceivedInputBlockCallback(aInputBlockId, isTouchPrevented);
+        sentContentResponse = true;
+      } else {
+        APZES_LOG("Event not prevented; pending response for %" PRIu64 " %s\n",
+                  aInputBlockId, ToString(aGuid).c_str());
+        mPendingTouchPreventedResponse = true;
+        mPendingTouchPreventedGuid = aGuid;
+        mPendingTouchPreventedBlockId = aInputBlockId;
+      }
+      break;
+    }
+
+    case eTouchEnd:
+      if (isTouchPrevented) {
+        mTouchEndCancelled = true;
+        mEndTouchIsClick = false;
+      }
+      [[fallthrough]];
+    case eTouchCancel:
+      mActiveElementManager->HandleTouchEndEvent(mEndTouchIsClick);
+      [[fallthrough]];
+    case eTouchMove: {
+      if (mPendingTouchPreventedResponse) {
+        MOZ_ASSERT(aGuid == mPendingTouchPreventedGuid);
+      }
+      sentContentResponse = SendPendingTouchPreventedResponse(isTouchPrevented);
+      break;
+    }
+
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unknown touch event type");
+      break;
+  }
+
+  mTouchCounter.Update(aEvent);
+  if (mTouchCounter.GetActiveTouchCount() == 0) {
+    mFirstTouchCancelled = false;
+  }
+
+  APZES_LOG("Pointercancel if %d %d %d %d %d\n", sentContentResponse,
+            !isTouchPrevented, aApzResponse == nsEventStatus_eConsumeDoDefault,
+            StaticPrefs::dom_w3c_pointer_events_enabled(),
+            MainThreadAgreesEventsAreConsumableByAPZ());
+  if (sentContentResponse && !isTouchPrevented &&
+      aApzResponse == nsEventStatus_eConsumeDoDefault &&
+      StaticPrefs::dom_w3c_pointer_events_enabled() &&
+      MainThreadAgreesEventsAreConsumableByAPZ()) {
+    WidgetTouchEvent cancelEvent(aEvent);
+    cancelEvent.mMessage = eTouchPointerCancel;
+    cancelEvent.mFlags.mCancelable = false;  // mMessage != eTouchCancel;
+    for (uint32_t i = 0; i < cancelEvent.mTouches.Length(); ++i) {
+      if (mozilla::dom::Touch* touch = cancelEvent.mTouches[i]) {
+        touch->convertToPointer = true;
+      }
+    }
+    nsEventStatus status;
+    cancelEvent.mWidget->DispatchEvent(&cancelEvent, status);
+  }
+}
+
+bool APZEventState::MainThreadAgreesEventsAreConsumableByAPZ() const {
+  // APZ errs on the side of saying it can consume touch events to perform
+  // default user-agent behaviours. In particular it may say this if it hasn't
+  // received accurate touch-action information. Here we double-check using
+  // accurate touch-action information. This code is kinda-sorta the main
+  // thread equivalent of AsyncPanZoomController::ArePointerEventsConsumable().
+
+  switch (mTouchBlockAllowedBehaviors.Length()) {
+    case 0:
+      // If we don't have any touch-action (e.g. because it is disabled) then
+      // APZ has no restrictions.
+      return true;
+
+    case 1: {
+      // If there's one touch point in this touch block, then check the pan-x
+      // and pan-y flags. If neither is allowed, then we disagree with APZ and
+      // say that it can't do anything with this touch block. Note that it would
+      // be even better if we could check the allowed scroll directions of the
+      // scrollframe at this point and refine this further.
+      TouchBehaviorFlags flags = mTouchBlockAllowedBehaviors[0];
+      return (flags & AllowedTouchBehavior::HORIZONTAL_PAN) ||
+             (flags & AllowedTouchBehavior::VERTICAL_PAN);
+    }
+
+    case 2: {
+      // If there's two touch points in this touch block, check that they both
+      // allow zooming.
+      for (const auto& allowed : mTouchBlockAllowedBehaviors) {
+        if (!(allowed & AllowedTouchBehavior::PINCH_ZOOM)) {
+          return false;
+        }
+      }
+      return true;
+    }
+
+    default:
+      // More than two touch points? APZ shouldn't be doing anything with this,
+      // so APZ shouldn't be consuming them.
+      return false;
+  }
+}
+
+void APZEventState::ProcessWheelEvent(const WidgetWheelEvent& aEvent,
+                                      uint64_t aInputBlockId) {
+  // If this event starts a swipe, indicate that it shouldn't result in a
+  // scroll by setting defaultPrevented to true.
+  bool defaultPrevented = aEvent.DefaultPrevented() || aEvent.TriggersSwipe();
+  mContentReceivedInputBlockCallback(aInputBlockId, defaultPrevented);
+}
+
+void APZEventState::ProcessMouseEvent(const WidgetMouseEvent& aEvent,
+                                      uint64_t aInputBlockId) {
+  bool defaultPrevented = false;
+  mContentReceivedInputBlockCallback(aInputBlockId, defaultPrevented);
+}
+
+void APZEventState::ProcessAPZStateChange(ViewID aViewId,
+                                          APZStateChange aChange, int aArg) {
+  switch (aChange) {
+    case APZStateChange::eTransformBegin: {
+      nsIScrollableFrame* sf = nsLayoutUtils::FindScrollableFrameFor(aViewId);
+      if (sf) {
+        sf->SetTransformingByAPZ(true);
+      }
+      nsIScrollbarMediator* scrollbarMediator = do_QueryFrame(sf);
+      if (scrollbarMediator) {
+        scrollbarMediator->ScrollbarActivityStarted();
+      }
+
+      nsIContent* content = nsLayoutUtils::FindContentFor(aViewId);
+      dom::Document* doc = content ? content->GetComposedDoc() : nullptr;
+      nsCOMPtr<nsIDocShell> docshell(doc ? doc->GetDocShell() : nullptr);
+      if (docshell && sf) {
+        nsDocShell* nsdocshell = static_cast<nsDocShell*>(docshell.get());
+        nsdocshell->NotifyAsyncPanZoomStarted();
+      }
+      break;
+    }
+    case APZStateChange::eTransformEnd: {
+      nsIScrollableFrame* sf = nsLayoutUtils::FindScrollableFrameFor(aViewId);
+      if (sf) {
+        sf->SetTransformingByAPZ(false);
+      }
+      nsIScrollbarMediator* scrollbarMediator = do_QueryFrame(sf);
+      if (scrollbarMediator) {
+        scrollbarMediator->ScrollbarActivityStopped();
+      }
+
+      nsIContent* content = nsLayoutUtils::FindContentFor(aViewId);
+      dom::Document* doc = content ? content->GetComposedDoc() : nullptr;
+      nsCOMPtr<nsIDocShell> docshell(doc ? doc->GetDocShell() : nullptr);
+      if (docshell && sf) {
+        nsDocShell* nsdocshell = static_cast<nsDocShell*>(docshell.get());
+        nsdocshell->NotifyAsyncPanZoomStopped();
+      }
+      break;
+    }
+    case APZStateChange::eStartTouch: {
+      mActiveElementManager->HandleTouchStart(aArg);
+      break;
+    }
+    case APZStateChange::eStartPanning: {
+      // The user started to pan, so we don't want anything to be :active.
+      mActiveElementManager->ClearActivation();
+      break;
+    }
+    case APZStateChange::eEndTouch: {
+      mEndTouchIsClick = aArg;
+      mActiveElementManager->HandleTouchEnd();
+      break;
+    }
+  }
+}
+
+bool APZEventState::SendPendingTouchPreventedResponse(bool aPreventDefault) {
+  if (mPendingTouchPreventedResponse) {
+    APZES_LOG("Sending response %d for pending guid: %s\n", aPreventDefault,
+              ToString(mPendingTouchPreventedGuid).c_str());
+    mContentReceivedInputBlockCallback(mPendingTouchPreventedBlockId,
+                                       aPreventDefault);
+    mPendingTouchPreventedResponse = false;
+    return true;
+  }
+  return false;
+}
+
+already_AddRefed<nsIWidget> APZEventState::GetWidget() const {
+  nsCOMPtr<nsIWidget> result = do_QueryReferent(mWidget);
+  return result.forget();
+}
+
+already_AddRefed<nsIContent> APZEventState::GetTouchRollup() const {
+  nsCOMPtr<nsIContent> result = do_QueryReferent(mTouchRollup);
+  return result.forget();
+}
+
+}  // namespace layers
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/APZEventState.h b/gfx/layers/apz/util/APZEventState.h
new file mode 100644
index 0000000000..60020f0f9a
--- /dev/null
+++ b/gfx/layers/apz/util/APZEventState.h
@@ -0,0 +1,124 @@
+/* -*- 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 mozilla_layers_APZEventState_h
+#define mozilla_layers_APZEventState_h
+
+#include <stdint.h>
+
+#include "Units.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/layers/GeckoContentControllerTypes.h"  // for APZStateChange
+#include "mozilla/layers/ScrollableLayerGuid.h"  // for ScrollableLayerGuid
+#include "mozilla/layers/TouchCounter.h"         // for TouchCounter
+#include "mozilla/RefPtr.h"
+#include "nsCOMPtr.h"
+#include "nsISupportsImpl.h"        // for NS_INLINE_DECL_REFCOUNTING
+#include "nsIWeakReferenceUtils.h"  // for nsWeakPtr
+
+#include <functional>
+
+template <class>
+class nsCOMPtr;
+class nsIContent;
+class nsIWidget;
+
+namespace mozilla {
+
+class PresShell;
+
+namespace layers {
+
+class ActiveElementManager;
+
+typedef std::function<void(uint64_t /* input block id */,
+                           bool /* prevent default */)>
+    ContentReceivedInputBlockCallback;
+
+/**
+ * A content-side component that keeps track of state for handling APZ
+ * gestures and sending APZ notifications.
+ */
+class APZEventState final {
+  typedef GeckoContentController_APZStateChange APZStateChange;
+  typedef ScrollableLayerGuid::ViewID ViewID;
+
+ public:
+  APZEventState(nsIWidget* aWidget,
+                ContentReceivedInputBlockCallback&& aCallback);
+
+  NS_INLINE_DECL_REFCOUNTING(APZEventState);
+
+  void ProcessSingleTap(const CSSPoint& aPoint,
+                        const CSSToLayoutDeviceScale& aScale,
+                        Modifiers aModifiers, int32_t aClickCount);
+  MOZ_CAN_RUN_SCRIPT
+  void ProcessLongTap(PresShell* aPresShell, const CSSPoint& aPoint,
+                      const CSSToLayoutDeviceScale& aScale,
+                      Modifiers aModifiers, uint64_t aInputBlockId);
+  MOZ_CAN_RUN_SCRIPT
+  void ProcessLongTapUp(PresShell* aPresShell, const CSSPoint& aPoint,
+                        const CSSToLayoutDeviceScale& aScale,
+                        Modifiers aModifiers);
+  void ProcessTouchEvent(const WidgetTouchEvent& aEvent,
+                         const ScrollableLayerGuid& aGuid,
+                         uint64_t aInputBlockId, nsEventStatus aApzResponse,
+                         nsEventStatus aContentResponse,
+                         nsTArray<TouchBehaviorFlags>&& aAllowedTouchBehaviors);
+  void ProcessWheelEvent(const WidgetWheelEvent& aEvent,
+                         uint64_t aInputBlockId);
+  void ProcessMouseEvent(const WidgetMouseEvent& aEvent,
+                         uint64_t aInputBlockId);
+  void ProcessAPZStateChange(ViewID aViewId, APZStateChange aChange, int aArg);
+  void ProcessClusterHit();
+
+ private:
+  ~APZEventState();
+  bool SendPendingTouchPreventedResponse(bool aPreventDefault);
+  MOZ_CAN_RUN_SCRIPT
+  bool FireContextmenuEvents(PresShell* aPresShell, const CSSPoint& aPoint,
+                             const CSSToLayoutDeviceScale& aScale,
+                             Modifiers aModifiers,
+                             const nsCOMPtr<nsIWidget>& aWidget);
+  already_AddRefed<nsIWidget> GetWidget() const;
+  already_AddRefed<nsIContent> GetTouchRollup() const;
+  bool MainThreadAgreesEventsAreConsumableByAPZ() const;
+
+ private:
+  nsWeakPtr mWidget;
+  RefPtr<ActiveElementManager> mActiveElementManager;
+  ContentReceivedInputBlockCallback mContentReceivedInputBlockCallback;
+  TouchCounter mTouchCounter;
+  bool mPendingTouchPreventedResponse;
+  ScrollableLayerGuid mPendingTouchPreventedGuid;
+  uint64_t mPendingTouchPreventedBlockId;
+  bool mEndTouchIsClick;
+  bool mFirstTouchCancelled;
+  bool mTouchEndCancelled;
+  int32_t mLastTouchIdentifier;
+  nsTArray<TouchBehaviorFlags> mTouchBlockAllowedBehaviors;
+
+  // Because touch-triggered mouse events (e.g. mouse events from a tap
+  // gesture) happen asynchronously from the touch events themselves, we
+  // need to stash and replicate some of the state from the touch events
+  // to the mouse events. One piece of state is the rollup content, which
+  // is the content for which a popup window was recently closed. If we
+  // don't replicate this state properly during the mouse events, the
+  // synthetic click might reopen a popup window that was just closed by
+  // the touch event, which is undesirable. See also documentation in
+  // nsAutoRollup.h
+  // Note that in cases where we get multiple touch blocks interleaved with
+  // their single-tap event notifications, mTouchRollup may hold an incorrect
+  // value. This is kind of an edge case, and falls in the same category of
+  // problems as bug 1227241. I intend that fixing that bug will also take
+  // care of this potential problem.
+  nsWeakPtr mTouchRollup;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /* mozilla_layers_APZEventState_h */
diff --git a/gfx/layers/apz/util/APZThreadUtils.cpp b/gfx/layers/apz/util/APZThreadUtils.cpp
new file mode 100644
index 0000000000..63db976834
--- /dev/null
+++ b/gfx/layers/apz/util/APZThreadUtils.cpp
@@ -0,0 +1,118 @@
+/* -*- 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 "APZThreadUtils.h"
+
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/StaticMutex.h"
+
+#include "nsISerialEventTarget.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+
+namespace mozilla {
+namespace layers {
+
+static bool sThreadAssertionsEnabled = true;
+static StaticRefPtr<nsISerialEventTarget> sControllerThread;
+static StaticMutex sControllerThreadMutex;
+
+/*static*/
+void APZThreadUtils::SetThreadAssertionsEnabled(bool aEnabled) {
+  StaticMutexAutoLock lock(sControllerThreadMutex);
+  sThreadAssertionsEnabled = aEnabled;
+}
+
+/*static*/
+bool APZThreadUtils::GetThreadAssertionsEnabled() {
+  StaticMutexAutoLock lock(sControllerThreadMutex);
+  return sThreadAssertionsEnabled;
+}
+
+/*static*/
+void APZThreadUtils::SetControllerThread(nsISerialEventTarget* aThread) {
+  // We must either be setting the initial controller thread, or removing it,
+  // or re-using an existing controller thread.
+  StaticMutexAutoLock lock(sControllerThreadMutex);
+  MOZ_ASSERT(!sControllerThread || !aThread || sControllerThread == aThread);
+  if (aThread != sControllerThread) {
+    // This can only happen once, on startup.
+    sControllerThread = aThread;
+    ClearOnShutdown(&sControllerThread);
+  }
+}
+
+/*static*/
+void APZThreadUtils::AssertOnControllerThread() {
+#if DEBUG
+  if (!GetThreadAssertionsEnabled()) {
+    return;
+  }
+  StaticMutexAutoLock lock(sControllerThreadMutex);
+  MOZ_ASSERT(sControllerThread && sControllerThread->IsOnCurrentThread());
+#endif
+}
+
+/*static*/
+void APZThreadUtils::RunOnControllerThread(RefPtr<Runnable>&& aTask) {
+  RefPtr<nsISerialEventTarget> thread;
+  {
+    StaticMutexAutoLock lock(sControllerThreadMutex);
+    thread = sControllerThread;
+  }
+  RefPtr<Runnable> task = std::move(aTask);
+
+  if (!thread) {
+    // Could happen on startup or if Shutdown() got called.
+    NS_WARNING("Dropping task posted to controller thread");
+    return;
+  }
+
+  if (thread->IsOnCurrentThread()) {
+    task->Run();
+  } else {
+    thread->Dispatch(task.forget());
+  }
+}
+
+/*static*/
+bool APZThreadUtils::IsControllerThread() {
+  StaticMutexAutoLock lock(sControllerThreadMutex);
+  return sControllerThread && sControllerThread->IsOnCurrentThread();
+}
+
+/*static*/
+bool APZThreadUtils::IsControllerThreadAlive() {
+  StaticMutexAutoLock lock(sControllerThreadMutex);
+  return !!sControllerThread;
+}
+
+/*static*/
+void APZThreadUtils::DelayedDispatch(already_AddRefed<Runnable> aRunnable,
+                                     int aDelayMs) {
+  MOZ_ASSERT(!XRE_IsContentProcess(),
+             "ContentProcessController should only be used remotely.");
+  RefPtr<nsISerialEventTarget> thread;
+  {
+    StaticMutexAutoLock lock(sControllerThreadMutex);
+    thread = sControllerThread;
+  }
+  if (!thread) {
+    // Could happen on startup
+    NS_WARNING("Dropping task posted to controller thread");
+    return;
+  }
+  if (aDelayMs) {
+    thread->DelayedDispatch(std::move(aRunnable), aDelayMs);
+  } else {
+    thread->Dispatch(std::move(aRunnable));
+  }
+}
+
+NS_IMPL_ISUPPORTS(GenericNamedTimerCallbackBase, nsITimerCallback, nsINamed)
+
+}  // namespace layers
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/APZThreadUtils.h b/gfx/layers/apz/util/APZThreadUtils.h
new file mode 100644
index 0000000000..fb03ac10da
--- /dev/null
+++ b/gfx/layers/apz/util/APZThreadUtils.h
@@ -0,0 +1,117 @@
+/* -*- 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 mozilla_layers_APZThreadUtils_h
+#define mozilla_layers_APZThreadUtils_h
+
+#include "nsINamed.h"
+#include "nsITimer.h"
+#include "nsString.h"
+
+class nsISerialEventTarget;
+
+namespace mozilla {
+
+class Runnable;
+
+namespace layers {
+
+class APZThreadUtils {
+ public:
+  /**
+   * In the gtest environment everything runs on one thread, so we
+   * shouldn't assert that we're on a particular thread. This enables
+   * that behaviour.
+   */
+  static void SetThreadAssertionsEnabled(bool aEnabled);
+  static bool GetThreadAssertionsEnabled();
+
+  /**
+   * Set the controller thread.
+   */
+  static void SetControllerThread(nsISerialEventTarget* aThread);
+
+  /**
+   * This can be used to assert that the current thread is the
+   * controller/UI thread (on which input events are received).
+   * This does nothing if thread assertions are disabled.
+   */
+  static void AssertOnControllerThread();
+
+  /**
+   * Run the given task on the APZ "controller thread" for this platform. If
+   * this function is called from the controller thread itself then the task is
+   * run immediately without getting queued.
+   */
+  static void RunOnControllerThread(RefPtr<Runnable>&& aTask);
+
+  /**
+   * Returns true if currently on APZ "controller thread".
+   */
+  static bool IsControllerThread();
+
+  /**
+   * Returns true if the controller thread is still alive.
+   */
+  static bool IsControllerThreadAlive();
+
+  /**
+   * Schedules a runnable to run on the controller thread at some time
+   * in the future.
+   */
+  static void DelayedDispatch(already_AddRefed<Runnable> aRunnable,
+                              int aDelayMs);
+};
+
+// A base class for GenericNamedTimerCallback<Function>.
+// This is necessary because NS_IMPL_ISUPPORTS doesn't work for a class
+// template.
+class GenericNamedTimerCallbackBase : public nsITimerCallback, public nsINamed {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+ protected:
+  virtual ~GenericNamedTimerCallbackBase() = default;
+};
+
+// An nsITimerCallback implementation with nsINamed that can be used with any
+// function object that's callable with no arguments.
+template <typename Function>
+class GenericNamedTimerCallback final : public GenericNamedTimerCallbackBase {
+ public:
+  GenericNamedTimerCallback(const Function& aFunction, const char* aName)
+      : mFunction(aFunction), mName(aName) {}
+
+  NS_IMETHOD Notify(nsITimer*) override {
+    mFunction();
+    return NS_OK;
+  }
+
+  NS_IMETHOD GetName(nsACString& aName) override {
+    aName = mName;
+    return NS_OK;
+  }
+
+ private:
+  Function mFunction;
+  nsCString mName;
+};
+
+// Convenience function for constructing a GenericNamedTimerCallback.
+// Returns a raw pointer, suitable for passing directly as an argument to
+// nsITimer::InitWithCallback(). The intention is to enable the following
+// terse inline usage:
+//    timer->InitWithCallback(NewNamedTimerCallback([](){ ... }, name), delay);
+template <typename Function>
+GenericNamedTimerCallback<Function>* NewNamedTimerCallback(
+    const Function& aFunction, const char* aName) {
+  return new GenericNamedTimerCallback<Function>(aFunction, aName);
+}
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /* mozilla_layers_APZThreadUtils_h */
diff --git a/gfx/layers/apz/util/ActiveElementManager.cpp b/gfx/layers/apz/util/ActiveElementManager.cpp
new file mode 100644
index 0000000000..ed485c3a1d
--- /dev/null
+++ b/gfx/layers/apz/util/ActiveElementManager.cpp
@@ -0,0 +1,178 @@
+/* -*- 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 "ActiveElementManager.h"
+#include "mozilla/EventStateManager.h"
+#include "mozilla/EventStates.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_ui.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/Document.h"
+
+static mozilla::LazyLogModule sApzAemLog("apz.activeelement");
+#define AEM_LOG(...) MOZ_LOG(sApzAemLog, LogLevel::Debug, (__VA_ARGS__))
+
+namespace mozilla {
+namespace layers {
+
+ActiveElementManager::ActiveElementManager()
+    : mCanBePan(false), mCanBePanSet(false), mSetActiveTask(nullptr) {}
+
+ActiveElementManager::~ActiveElementManager() = default;
+
+void ActiveElementManager::SetTargetElement(dom::EventTarget* aTarget) {
+  if (mTarget) {
+    // Multiple fingers on screen (since HandleTouchEnd clears mTarget).
+    AEM_LOG("Multiple fingers on-screen, clearing target element\n");
+    CancelTask();
+    ResetActive();
+    ResetTouchBlockState();
+    return;
+  }
+
+  mTarget = do_QueryInterface(aTarget);
+  AEM_LOG("Setting target element to %p\n", mTarget.get());
+  TriggerElementActivation();
+}
+
+void ActiveElementManager::HandleTouchStart(bool aCanBePan) {
+  AEM_LOG("Touch start, aCanBePan: %d\n", aCanBePan);
+  if (mCanBePanSet) {
+    // Multiple fingers on screen (since HandleTouchEnd clears mCanBePanSet).
+    AEM_LOG("Multiple fingers on-screen, clearing touch block state\n");
+    CancelTask();
+    ResetActive();
+    ResetTouchBlockState();
+    return;
+  }
+
+  mCanBePan = aCanBePan;
+  mCanBePanSet = true;
+  TriggerElementActivation();
+}
+
+void ActiveElementManager::TriggerElementActivation() {
+  // Both HandleTouchStart() and SetTargetElement() call this. They can be
+  // called in either order. One will set mCanBePanSet, and the other, mTarget.
+  // We want to actually trigger the activation once both are set.
+  if (!(mTarget && mCanBePanSet)) {
+    return;
+  }
+
+  // If the touch cannot be a pan, make mTarget :active right away.
+  // Otherwise, wait a bit to see if the user will pan or not.
+  if (!mCanBePan) {
+    SetActive(mTarget);
+  } else {
+    CancelTask();  // this is only needed because of bug 1169802. Fixing that
+                   // bug properly should make this unnecessary.
+    MOZ_ASSERT(mSetActiveTask == nullptr);
+
+    RefPtr<CancelableRunnable> task =
+        NewCancelableRunnableMethod<nsCOMPtr<dom::Element>>(
+            "layers::ActiveElementManager::SetActiveTask", this,
+            &ActiveElementManager::SetActiveTask, mTarget);
+    mSetActiveTask = task;
+    NS_GetCurrentThread()->DelayedDispatch(
+        task.forget(), StaticPrefs::ui_touch_activation_delay_ms());
+    AEM_LOG("Scheduling mSetActiveTask %p\n", mSetActiveTask.get());
+  }
+}
+
+void ActiveElementManager::ClearActivation() {
+  AEM_LOG("Clearing element activation\n");
+  CancelTask();
+  ResetActive();
+}
+
+void ActiveElementManager::HandleTouchEndEvent(bool aWasClick) {
+  AEM_LOG("Touch end event, aWasClick: %d\n", aWasClick);
+
+  // If the touch was a click, make mTarget :active right away.
+  // nsEventStateManager will reset the active element when processing
+  // the mouse-down event generated by the click.
+  CancelTask();
+  if (aWasClick) {
+    // Scrollbar thumbs use a different mechanism for their active
+    // highlight (the "active" attribute), so don't set the active state
+    // on them because nothing will clear it.
+    if (!(mTarget && mTarget->IsXULElement(nsGkAtoms::thumb))) {
+      SetActive(mTarget);
+    }
+  } else {
+    // We might reach here if mCanBePan was false on touch-start and
+    // so we set the element active right away. Now it turns out the
+    // action was not a click so we need to reset the active element.
+    ResetActive();
+  }
+
+  ResetTouchBlockState();
+}
+
+void ActiveElementManager::HandleTouchEnd() {
+  AEM_LOG("Touch end, clearing pan state\n");
+  mCanBePanSet = false;
+}
+
+static nsPresContext* GetPresContextFor(nsIContent* aContent) {
+  if (!aContent) {
+    return nullptr;
+  }
+  PresShell* presShell = aContent->OwnerDoc()->GetPresShell();
+  if (!presShell) {
+    return nullptr;
+  }
+  return presShell->GetPresContext();
+}
+
+void ActiveElementManager::SetActive(dom::Element* aTarget) {
+  AEM_LOG("Setting active %p\n", aTarget);
+
+  if (nsPresContext* pc = GetPresContextFor(aTarget)) {
+    pc->EventStateManager()->SetContentState(aTarget, NS_EVENT_STATE_ACTIVE);
+  }
+}
+
+void ActiveElementManager::ResetActive() {
+  AEM_LOG("Resetting active from %p\n", mTarget.get());
+
+  // Clear the :active flag from mTarget by setting it on the document root.
+  if (mTarget) {
+    dom::Element* root = mTarget->OwnerDoc()->GetDocumentElement();
+    if (root) {
+      AEM_LOG("Found root %p, making active\n", root);
+      SetActive(root);
+    }
+  }
+}
+
+void ActiveElementManager::ResetTouchBlockState() {
+  mTarget = nullptr;
+  mCanBePanSet = false;
+}
+
+void ActiveElementManager::SetActiveTask(
+    const nsCOMPtr<dom::Element>& aTarget) {
+  AEM_LOG("mSetActiveTask %p running\n", mSetActiveTask.get());
+
+  // This gets called from mSetActiveTask's Run() method. The message loop
+  // deletes the task right after running it, so we need to null out
+  // mSetActiveTask to make sure we're not left with a dangling pointer.
+  mSetActiveTask = nullptr;
+  SetActive(aTarget);
+}
+
+void ActiveElementManager::CancelTask() {
+  AEM_LOG("Cancelling task %p\n", mSetActiveTask.get());
+
+  if (mSetActiveTask) {
+    mSetActiveTask->Cancel();
+    mSetActiveTask = nullptr;
+  }
+}
+
+}  // namespace layers
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/ActiveElementManager.h b/gfx/layers/apz/util/ActiveElementManager.h
new file mode 100644
index 0000000000..b783659962
--- /dev/null
+++ b/gfx/layers/apz/util/ActiveElementManager.h
@@ -0,0 +1,97 @@
+/* -*- 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 mozilla_layers_ActiveElementManager_h
+#define mozilla_layers_ActiveElementManager_h
+
+#include "nsCOMPtr.h"
+#include "nsISupportsImpl.h"
+
+namespace mozilla {
+
+class CancelableRunnable;
+
+namespace dom {
+class Element;
+class EventTarget;
+}  // namespace dom
+
+namespace layers {
+
+/**
+ * Manages setting and clearing the ':active' CSS pseudostate in the presence
+ * of touch input.
+ */
+class ActiveElementManager final {
+  ~ActiveElementManager();
+
+ public:
+  NS_INLINE_DECL_REFCOUNTING(ActiveElementManager)
+
+  ActiveElementManager();
+
+  /**
+   * Specify the target of a touch. Typically this should be called right
+   * after HandleTouchStart(), but in cases where the APZ needs to wait for
+   * a content response the HandleTouchStart() may be delayed, in which case
+   * this function can be called first.
+   * |aTarget| may be nullptr.
+   */
+  void SetTargetElement(dom::EventTarget* aTarget);
+  /**
+   * Handle a touch-start state notification from APZ. This notification
+   * may be delayed until after touch listeners have responded to the APZ.
+   * @param aCanBePan whether the touch can be a pan
+   */
+  void HandleTouchStart(bool aCanBePan);
+  /**
+   * Clear the active element.
+   */
+  void ClearActivation();
+  /**
+   * Handle a touch-end or touch-cancel event.
+   * @param aWasClick whether the touch was a click
+   */
+  void HandleTouchEndEvent(bool aWasClick);
+  /**
+   * Handle a touch-end state notification from APZ. This notification may be
+   * delayed until after touch listeners have responded to the APZ.
+   */
+  void HandleTouchEnd();
+
+ private:
+  /**
+   * The target of the first touch point in the current touch block.
+   */
+  nsCOMPtr<dom::Element> mTarget;
+  /**
+   * Whether the current touch block can be a pan. Set in HandleTouchStart().
+   */
+  bool mCanBePan;
+  /**
+   * Whether mCanBePan has been set for the current touch block.
+   * We need to keep track of this to allow HandleTouchStart() and
+   * SetTargetElement() to be called in either order.
+   */
+  bool mCanBePanSet;
+  /**
+   * A task for calling SetActive() after a timeout.
+   */
+  RefPtr<CancelableRunnable> mSetActiveTask;
+
+  // Helpers
+  void TriggerElementActivation();
+  void SetActive(dom::Element* aTarget);
+  void ResetActive();
+  void ResetTouchBlockState();
+  void SetActiveTask(const nsCOMPtr<dom::Element>& aTarget);
+  void CancelTask();
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /* mozilla_layers_ActiveElementManager_h */
diff --git a/gfx/layers/apz/util/CheckerboardReportService.cpp b/gfx/layers/apz/util/CheckerboardReportService.cpp
new file mode 100644
index 0000000000..24668deecf
--- /dev/null
+++ b/gfx/layers/apz/util/CheckerboardReportService.cpp
@@ -0,0 +1,219 @@
+/* -*- 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 "CheckerboardReportService.h"
+
+#include "jsapi.h"                    // for JS_Now
+#include "MainThreadUtils.h"          // for NS_IsMainThread
+#include "mozilla/Assertions.h"       // for MOZ_ASSERT
+#include "mozilla/ClearOnShutdown.h"  // for ClearOnShutdown
+#include "mozilla/Preferences.h"
+#include "mozilla/Services.h"
+#include "mozilla/StaticPrefs_apz.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/CheckerboardReportServiceBinding.h"  // for dom::CheckerboardReports
+#include "mozilla/gfx/GPUParent.h"
+#include "mozilla/gfx/GPUProcessManager.h"
+#include "nsContentUtils.h"  // for nsContentUtils
+#include "nsIObserverService.h"
+#include "nsXULAppAPI.h"
+
+namespace mozilla {
+namespace layers {
+
+/*static*/
+StaticRefPtr<CheckerboardEventStorage> CheckerboardEventStorage::sInstance;
+
+/*static*/
+already_AddRefed<CheckerboardEventStorage>
+CheckerboardEventStorage::GetInstance() {
+  // The instance in the parent process does all the work, so if this is getting
+  // called in the child process something is likely wrong.
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!sInstance) {
+    sInstance = new CheckerboardEventStorage();
+    ClearOnShutdown(&sInstance);
+  }
+  RefPtr<CheckerboardEventStorage> instance = sInstance.get();
+  return instance.forget();
+}
+
+void CheckerboardEventStorage::Report(uint32_t aSeverity,
+                                      const std::string& aLog) {
+  if (!NS_IsMainThread()) {
+    RefPtr<Runnable> task = NS_NewRunnableFunction(
+        "layers::CheckerboardEventStorage::Report",
+        [aSeverity, aLog]() -> void {
+          CheckerboardEventStorage::Report(aSeverity, aLog);
+        });
+    NS_DispatchToMainThread(task.forget());
+    return;
+  }
+
+  if (XRE_IsGPUProcess()) {
+    if (gfx::GPUParent* gpu = gfx::GPUParent::GetSingleton()) {
+      nsCString log(aLog.c_str());
+      Unused << gpu->SendReportCheckerboard(aSeverity, log);
+    }
+    return;
+  }
+
+  RefPtr<CheckerboardEventStorage> storage = GetInstance();
+  storage->ReportCheckerboard(aSeverity, aLog);
+}
+
+void CheckerboardEventStorage::ReportCheckerboard(uint32_t aSeverity,
+                                                  const std::string& aLog) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (aSeverity == 0) {
+    // This code assumes all checkerboard reports have a nonzero severity.
+    return;
+  }
+
+  CheckerboardReport severe(aSeverity, JS_Now(), aLog);
+  CheckerboardReport recent;
+
+  // First look in the "severe" reports to see if the new one belongs in that
+  // list.
+  for (int i = 0; i < SEVERITY_MAX_INDEX; i++) {
+    if (mCheckerboardReports[i].mSeverity >= severe.mSeverity) {
+      continue;
+    }
+    // The new one deserves to be in the "severe" list. Take the one getting
+    // bumped off the list, and put it in |recent| for possible insertion into
+    // the recents list.
+    recent = mCheckerboardReports[SEVERITY_MAX_INDEX - 1];
+
+    // Shuffle the severe list down, insert the new one.
+    for (int j = SEVERITY_MAX_INDEX - 1; j > i; j--) {
+      mCheckerboardReports[j] = mCheckerboardReports[j - 1];
+    }
+    mCheckerboardReports[i] = severe;
+    severe.mSeverity = 0;  // mark |severe| as inserted
+    break;
+  }
+
+  // If |severe.mSeverity| is nonzero, the incoming report didn't get inserted
+  // into the severe list; put it into |recent| for insertion into the recent
+  // list.
+  if (severe.mSeverity) {
+    MOZ_ASSERT(recent.mSeverity == 0, "recent should be empty here");
+    recent = severe;
+  }  // else |recent| may hold a report that got knocked out of the severe list.
+
+  if (recent.mSeverity == 0) {
+    // Nothing to be inserted into the recent list.
+    return;
+  }
+
+  // If it wasn't in the "severe" list, add it to the "recent" list.
+  for (int i = SEVERITY_MAX_INDEX; i < RECENT_MAX_INDEX; i++) {
+    if (mCheckerboardReports[i].mTimestamp >= recent.mTimestamp) {
+      continue;
+    }
+    // |recent| needs to be inserted at |i|. Shuffle the remaining ones down
+    // and insert it.
+    for (int j = RECENT_MAX_INDEX - 1; j > i; j--) {
+      mCheckerboardReports[j] = mCheckerboardReports[j - 1];
+    }
+    mCheckerboardReports[i] = recent;
+    break;
+  }
+}
+
+void CheckerboardEventStorage::GetReports(
+    nsTArray<dom::CheckerboardReport>& aOutReports) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  for (int i = 0; i < RECENT_MAX_INDEX; i++) {
+    CheckerboardReport& r = mCheckerboardReports[i];
+    if (r.mSeverity == 0) {
+      continue;
+    }
+    dom::CheckerboardReport report;
+    report.mSeverity.Construct() = r.mSeverity;
+    report.mTimestamp.Construct() = r.mTimestamp / 1000;  // micros to millis
+    report.mLog.Construct() =
+        NS_ConvertUTF8toUTF16(r.mLog.c_str(), r.mLog.size());
+    report.mReason.Construct() = (i < SEVERITY_MAX_INDEX)
+                                     ? dom::CheckerboardReason::Severe
+                                     : dom::CheckerboardReason::Recent;
+    aOutReports.AppendElement(report);
+  }
+}
+
+}  // namespace layers
+
+namespace dom {
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(CheckerboardReportService, mParent)
+NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(CheckerboardReportService, AddRef)
+NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(CheckerboardReportService, Release)
+
+/*static*/
+bool CheckerboardReportService::IsEnabled(JSContext* aCtx, JSObject* aGlobal) {
+  // Only allow this in the parent process
+  if (!XRE_IsParentProcess()) {
+    return false;
+  }
+  // Allow privileged code or about:checkerboard (unprivileged) to access this.
+  return nsContentUtils::IsSystemCaller(aCtx) ||
+         nsContentUtils::IsSpecificAboutPage(aGlobal, "about:checkerboard");
+}
+
+/*static*/
+already_AddRefed<CheckerboardReportService>
+CheckerboardReportService::Constructor(const dom::GlobalObject& aGlobal) {
+  RefPtr<CheckerboardReportService> ces =
+      new CheckerboardReportService(aGlobal.GetAsSupports());
+  return ces.forget();
+}
+
+CheckerboardReportService::CheckerboardReportService(nsISupports* aParent)
+    : mParent(aParent) {}
+
+JSObject* CheckerboardReportService::WrapObject(
+    JSContext* aCtx, JS::Handle<JSObject*> aGivenProto) {
+  return CheckerboardReportService_Binding::Wrap(aCtx, this, aGivenProto);
+}
+
+nsISupports* CheckerboardReportService::GetParentObject() { return mParent; }
+
+void CheckerboardReportService::GetReports(
+    nsTArray<dom::CheckerboardReport>& aOutReports) {
+  RefPtr<mozilla::layers::CheckerboardEventStorage> instance =
+      mozilla::layers::CheckerboardEventStorage::GetInstance();
+  MOZ_ASSERT(instance);
+  instance->GetReports(aOutReports);
+}
+
+bool CheckerboardReportService::IsRecordingEnabled() const {
+  return StaticPrefs::apz_record_checkerboarding();
+}
+
+void CheckerboardReportService::SetRecordingEnabled(bool aEnabled) {
+  Preferences::SetBool("apz.record_checkerboarding", aEnabled);
+}
+
+void CheckerboardReportService::FlushActiveReports() {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  gfx::GPUProcessManager* gpu = gfx::GPUProcessManager::Get();
+  if (gpu && gpu->NotifyGpuObservers("APZ:FlushActiveCheckerboard")) {
+    return;
+  }
+
+  nsCOMPtr<nsIObserverService> obsSvc = mozilla::services::GetObserverService();
+  MOZ_ASSERT(obsSvc);
+  if (obsSvc) {
+    obsSvc->NotifyObservers(nullptr, "APZ:FlushActiveCheckerboard", nullptr);
+  }
+}
+
+}  // namespace dom
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/CheckerboardReportService.h b/gfx/layers/apz/util/CheckerboardReportService.h
new file mode 100644
index 0000000000..3062255f95
--- /dev/null
+++ b/gfx/layers/apz/util/CheckerboardReportService.h
@@ -0,0 +1,138 @@
+/* -*- 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 mozilla_dom_CheckerboardReportService_h
+#define mozilla_dom_CheckerboardReportService_h
+
+#include <string>
+
+#include "js/TypeDecls.h"            // for JSContext, JSObject
+#include "mozilla/StaticPtr.h"       // for StaticRefPtr
+#include "nsCOMPtr.h"                // for nsCOMPtr
+#include "nsISupports.h"             // for NS_INLINE_DECL_REFCOUNTING
+#include "nsTArrayForwardDeclare.h"  // for nsTArray
+#include "nsWrapperCache.h"          // for nsWrapperCache
+
+namespace mozilla {
+
+namespace dom {
+struct CheckerboardReport;
+}
+
+namespace layers {
+
+// CheckerboardEventStorage is a singleton that stores info on checkerboard
+// events, so that they can be accessed from about:checkerboard and visualized.
+// Note that this class is NOT threadsafe, and all methods must be called on
+// the main thread.
+class CheckerboardEventStorage {
+  NS_INLINE_DECL_REFCOUNTING(CheckerboardEventStorage)
+
+ public:
+  /**
+   * Get the singleton instance.
+   */
+  static already_AddRefed<CheckerboardEventStorage> GetInstance();
+
+  /**
+   * Get the stored checkerboard reports.
+   */
+  void GetReports(nsTArray<dom::CheckerboardReport>& aOutReports);
+
+  /**
+   * Save a checkerboard event log, optionally dropping older ones that were
+   * less severe or less recent. Zero-severity reports may be ignored entirely.
+   */
+  static void Report(uint32_t aSeverity, const std::string& aLog);
+
+ private:
+  /* Stuff for refcounted singleton */
+  CheckerboardEventStorage() = default;
+  virtual ~CheckerboardEventStorage() = default;
+
+  static StaticRefPtr<CheckerboardEventStorage> sInstance;
+
+  void ReportCheckerboard(uint32_t aSeverity, const std::string& aLog);
+
+ private:
+  /**
+   * Struct that this class uses internally to store a checkerboard report.
+   */
+  struct CheckerboardReport {
+    uint32_t mSeverity;  // if 0, this report is empty
+    int64_t mTimestamp;  // microseconds since epoch, as from JS_Now()
+    std::string mLog;
+
+    CheckerboardReport() : mSeverity(0), mTimestamp(0) {}
+
+    CheckerboardReport(uint32_t aSeverity, int64_t aTimestamp,
+                       const std::string& aLog)
+        : mSeverity(aSeverity), mTimestamp(aTimestamp), mLog(aLog) {}
+  };
+
+  // The first 5 (indices 0-4) are the most severe ones in decreasing order
+  // of severity; the next 5 (indices 5-9) are the most recent ones that are
+  // not already in the "severe" list.
+  static const int SEVERITY_MAX_INDEX = 5;
+  static const int RECENT_MAX_INDEX = 10;
+  CheckerboardReport mCheckerboardReports[RECENT_MAX_INDEX];
+};
+
+}  // namespace layers
+
+namespace dom {
+
+class GlobalObject;
+
+/**
+ * CheckerboardReportService is a wrapper object that allows access to the
+ * stuff in CheckerboardEventStorage (above). We need this wrapper for proper
+ * garbage/cycle collection, since this can be accessed from JS.
+ */
+class CheckerboardReportService : public nsWrapperCache {
+ public:
+  /**
+   * Check if the given page is allowed to access this object via the WebIDL
+   * bindings. It only returns true if the page is about:checkerboard.
+   */
+  static bool IsEnabled(JSContext* aCtx, JSObject* aGlobal);
+
+  /*
+   * Other standard WebIDL binding glue.
+   */
+
+  static already_AddRefed<CheckerboardReportService> Constructor(
+      const dom::GlobalObject& aGlobal);
+
+  explicit CheckerboardReportService(nsISupports* aSupports);
+
+  JSObject* WrapObject(JSContext* aCtx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  nsISupports* GetParentObject();
+
+  NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(CheckerboardReportService)
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_NATIVE_CLASS(CheckerboardReportService)
+
+ public:
+  /*
+   * The methods exposed via the webidl.
+   */
+  void GetReports(nsTArray<dom::CheckerboardReport>& aOutReports);
+  bool IsRecordingEnabled() const;
+  void SetRecordingEnabled(bool aEnabled);
+  void FlushActiveReports();
+
+ private:
+  virtual ~CheckerboardReportService() = default;
+
+  nsCOMPtr<nsISupports> mParent;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif /* mozilla_layers_CheckerboardReportService_h */
diff --git a/gfx/layers/apz/util/ChromeProcessController.cpp b/gfx/layers/apz/util/ChromeProcessController.cpp
new file mode 100644
index 0000000000..0f907f8049
--- /dev/null
+++ b/gfx/layers/apz/util/ChromeProcessController.cpp
@@ -0,0 +1,335 @@
+/* -*- 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 "ChromeProcessController.h"
+
+#include "MainThreadUtils.h"  // for NS_IsMainThread()
+#include "base/task.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/layers/CompositorBridgeParent.h"
+#include "mozilla/layers/APZCCallbackHelper.h"
+#include "mozilla/layers/APZEventState.h"
+#include "mozilla/layers/APZThreadUtils.h"
+#include "mozilla/layers/IAPZCTreeManager.h"
+#include "mozilla/layers/InputAPZContext.h"
+#include "mozilla/layers/DoubleTapToZoom.h"
+#include "mozilla/layers/RepaintRequest.h"
+#include "mozilla/dom/Document.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsLayoutUtils.h"
+#include "nsView.h"
+
+static mozilla::LazyLogModule sApzChromeLog("apz.cc.chrome");
+
+using namespace mozilla;
+using namespace mozilla::layers;
+using namespace mozilla::widget;
+
+ChromeProcessController::ChromeProcessController(
+    nsIWidget* aWidget, APZEventState* aAPZEventState,
+    IAPZCTreeManager* aAPZCTreeManager)
+    : mWidget(aWidget),
+      mAPZEventState(aAPZEventState),
+      mAPZCTreeManager(aAPZCTreeManager),
+      mUIThread(NS_GetCurrentThread()) {
+  // Otherwise we're initializing mUIThread incorrectly.
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aAPZEventState);
+  MOZ_ASSERT(aAPZCTreeManager);
+
+  mUIThread->Dispatch(
+      NewRunnableMethod("layers::ChromeProcessController::InitializeRoot", this,
+                        &ChromeProcessController::InitializeRoot));
+}
+
+ChromeProcessController::~ChromeProcessController() = default;
+
+void ChromeProcessController::InitializeRoot() {
+  APZCCallbackHelper::InitializeRootDisplayport(GetPresShell());
+}
+
+void ChromeProcessController::NotifyLayerTransforms(
+    nsTArray<MatrixMessage>&& aTransforms) {
+  if (!mUIThread->IsOnCurrentThread()) {
+    mUIThread->Dispatch(
+        NewRunnableMethod<StoreCopyPassByRRef<nsTArray<MatrixMessage>>>(
+            "layers::ChromeProcessController::NotifyLayerTransforms", this,
+            &ChromeProcessController::NotifyLayerTransforms,
+            std::move(aTransforms)));
+    return;
+  }
+
+  APZCCallbackHelper::NotifyLayerTransforms(aTransforms);
+}
+
+void ChromeProcessController::RequestContentRepaint(
+    const RepaintRequest& aRequest) {
+  MOZ_ASSERT(IsRepaintThread());
+
+  if (aRequest.IsRootContent()) {
+    APZCCallbackHelper::UpdateRootFrame(aRequest);
+  } else {
+    APZCCallbackHelper::UpdateSubFrame(aRequest);
+  }
+}
+
+bool ChromeProcessController::IsRepaintThread() { return NS_IsMainThread(); }
+
+void ChromeProcessController::DispatchToRepaintThread(
+    already_AddRefed<Runnable> aTask) {
+  NS_DispatchToMainThread(std::move(aTask));
+}
+
+void ChromeProcessController::Destroy() {
+  if (!mUIThread->IsOnCurrentThread()) {
+    mUIThread->Dispatch(
+        NewRunnableMethod("layers::ChromeProcessController::Destroy", this,
+                          &ChromeProcessController::Destroy));
+    return;
+  }
+
+  MOZ_ASSERT(mUIThread->IsOnCurrentThread());
+  mWidget = nullptr;
+  mAPZEventState = nullptr;
+}
+
+PresShell* ChromeProcessController::GetPresShell() const {
+  if (!mWidget) {
+    return nullptr;
+  }
+  if (nsView* view = nsView::GetViewFor(mWidget)) {
+    return view->GetPresShell();
+  }
+  return nullptr;
+}
+
+dom::Document* ChromeProcessController::GetRootDocument() const {
+  if (PresShell* presShell = GetPresShell()) {
+    return presShell->GetDocument();
+  }
+  return nullptr;
+}
+
+dom::Document* ChromeProcessController::GetRootContentDocument(
+    const ScrollableLayerGuid::ViewID& aScrollId) const {
+  nsIContent* content = nsLayoutUtils::FindContentFor(aScrollId);
+  if (!content) {
+    return nullptr;
+  }
+  if (PresShell* presShell =
+          APZCCallbackHelper::GetRootContentDocumentPresShellForContent(
+              content)) {
+    return presShell->GetDocument();
+  }
+  return nullptr;
+}
+
+void ChromeProcessController::HandleDoubleTap(
+    const mozilla::CSSPoint& aPoint, Modifiers aModifiers,
+    const ScrollableLayerGuid& aGuid) {
+  MOZ_ASSERT(mUIThread->IsOnCurrentThread());
+
+  RefPtr<dom::Document> document = GetRootContentDocument(aGuid.mScrollId);
+  if (!document.get()) {
+    return;
+  }
+
+  CSSRect zoomToRect = CalculateRectToZoomTo(document, aPoint);
+
+  uint32_t presShellId;
+  ScrollableLayerGuid::ViewID viewId;
+  if (APZCCallbackHelper::GetOrCreateScrollIdentifiers(
+          document->GetDocumentElement(), &presShellId, &viewId)) {
+    APZThreadUtils::RunOnControllerThread(
+        NewRunnableMethod<ScrollableLayerGuid, CSSRect, uint32_t>(
+            "IAPZCTreeManager::ZoomToRect", mAPZCTreeManager,
+            &IAPZCTreeManager::ZoomToRect,
+            ScrollableLayerGuid(aGuid.mLayersId, presShellId, viewId),
+            zoomToRect, ZoomToRectBehavior::DEFAULT_BEHAVIOR));
+  }
+}
+
+void ChromeProcessController::HandleTap(
+    TapType aType, const mozilla::LayoutDevicePoint& aPoint,
+    Modifiers aModifiers, const ScrollableLayerGuid& aGuid,
+    uint64_t aInputBlockId) {
+  MOZ_LOG(sApzChromeLog, LogLevel::Debug,
+          ("HandleTap called with %d\n", (int)aType));
+  if (!mUIThread->IsOnCurrentThread()) {
+    MOZ_LOG(sApzChromeLog, LogLevel::Debug, ("HandleTap redispatching\n"));
+    mUIThread->Dispatch(
+        NewRunnableMethod<TapType, mozilla::LayoutDevicePoint, Modifiers,
+                          ScrollableLayerGuid, uint64_t>(
+            "layers::ChromeProcessController::HandleTap", this,
+            &ChromeProcessController::HandleTap, aType, aPoint, aModifiers,
+            aGuid, aInputBlockId));
+    return;
+  }
+
+  if (!mAPZEventState) {
+    return;
+  }
+
+  RefPtr<PresShell> presShell = GetPresShell();
+  if (!presShell) {
+    return;
+  }
+  if (!presShell->GetPresContext()) {
+    return;
+  }
+  CSSToLayoutDeviceScale scale(
+      presShell->GetPresContext()->CSSToDevPixelScale());
+
+  CSSPoint point = aPoint / scale;
+
+  // Stash the guid in InputAPZContext so that when the visual-to-layout
+  // transform is applied to the event's coordinates, we use the right transform
+  // based on the scroll frame being targeted.
+  // The other values don't really matter.
+  InputAPZContext context(aGuid, aInputBlockId, nsEventStatus_eSentinel);
+
+  switch (aType) {
+    case TapType::eSingleTap:
+      mAPZEventState->ProcessSingleTap(point, scale, aModifiers, 1);
+      break;
+    case TapType::eDoubleTap:
+      HandleDoubleTap(point, aModifiers, aGuid);
+      break;
+    case TapType::eSecondTap:
+      mAPZEventState->ProcessSingleTap(point, scale, aModifiers, 2);
+      break;
+    case TapType::eLongTap: {
+      RefPtr<APZEventState> eventState(mAPZEventState);
+      eventState->ProcessLongTap(presShell, point, scale, aModifiers,
+                                 aInputBlockId);
+      break;
+    }
+    case TapType::eLongTapUp: {
+      RefPtr<APZEventState> eventState(mAPZEventState);
+      eventState->ProcessLongTapUp(presShell, point, scale, aModifiers);
+      break;
+    }
+  }
+}
+
+void ChromeProcessController::NotifyPinchGesture(
+    PinchGestureInput::PinchGestureType aType, const ScrollableLayerGuid& aGuid,
+    const LayoutDevicePoint& aFocusPoint, LayoutDeviceCoord aSpanChange,
+    Modifiers aModifiers) {
+  if (!mUIThread->IsOnCurrentThread()) {
+    mUIThread->Dispatch(
+        NewRunnableMethod<PinchGestureInput::PinchGestureType,
+                          ScrollableLayerGuid, LayoutDevicePoint,
+                          LayoutDeviceCoord, Modifiers>(
+            "layers::ChromeProcessController::NotifyPinchGesture", this,
+            &ChromeProcessController::NotifyPinchGesture, aType, aGuid,
+            aFocusPoint, aSpanChange, aModifiers));
+    return;
+  }
+
+  if (mWidget) {
+    // Dispatch the call to APZCCallbackHelper::NotifyPinchGesture to the main
+    // thread so that it runs asynchronously from the current call. This is
+    // because the call can run arbitrary JS code, which can also spin the event
+    // loop and cause undesirable re-entrancy in APZ.
+    mUIThread->Dispatch(NewRunnableFunction(
+        "layers::ChromeProcessController::NotifyPinchGestureAsync",
+        &APZCCallbackHelper::NotifyPinchGesture, aType, aFocusPoint,
+        aSpanChange, aModifiers, mWidget));
+  }
+}
+
+void ChromeProcessController::NotifyAPZStateChange(
+    const ScrollableLayerGuid& aGuid, APZStateChange aChange, int aArg) {
+  if (!mUIThread->IsOnCurrentThread()) {
+    mUIThread->Dispatch(
+        NewRunnableMethod<ScrollableLayerGuid, APZStateChange, int>(
+            "layers::ChromeProcessController::NotifyAPZStateChange", this,
+            &ChromeProcessController::NotifyAPZStateChange, aGuid, aChange,
+            aArg));
+    return;
+  }
+
+  if (!mAPZEventState) {
+    return;
+  }
+
+  mAPZEventState->ProcessAPZStateChange(aGuid.mScrollId, aChange, aArg);
+}
+
+void ChromeProcessController::NotifyMozMouseScrollEvent(
+    const ScrollableLayerGuid::ViewID& aScrollId, const nsString& aEvent) {
+  if (!mUIThread->IsOnCurrentThread()) {
+    mUIThread->Dispatch(
+        NewRunnableMethod<ScrollableLayerGuid::ViewID, nsString>(
+            "layers::ChromeProcessController::NotifyMozMouseScrollEvent", this,
+            &ChromeProcessController::NotifyMozMouseScrollEvent, aScrollId,
+            aEvent));
+    return;
+  }
+
+  APZCCallbackHelper::NotifyMozMouseScrollEvent(aScrollId, aEvent);
+}
+
+void ChromeProcessController::NotifyFlushComplete() {
+  MOZ_ASSERT(IsRepaintThread());
+
+  APZCCallbackHelper::NotifyFlushComplete(GetPresShell());
+}
+
+void ChromeProcessController::NotifyAsyncScrollbarDragInitiated(
+    uint64_t aDragBlockId, const ScrollableLayerGuid::ViewID& aScrollId,
+    ScrollDirection aDirection) {
+  if (!mUIThread->IsOnCurrentThread()) {
+    mUIThread->Dispatch(NewRunnableMethod<uint64_t, ScrollableLayerGuid::ViewID,
+                                          ScrollDirection>(
+        "layers::ChromeProcessController::NotifyAsyncScrollbarDragInitiated",
+        this, &ChromeProcessController::NotifyAsyncScrollbarDragInitiated,
+        aDragBlockId, aScrollId, aDirection));
+    return;
+  }
+
+  APZCCallbackHelper::NotifyAsyncScrollbarDragInitiated(aDragBlockId, aScrollId,
+                                                        aDirection);
+}
+
+void ChromeProcessController::NotifyAsyncScrollbarDragRejected(
+    const ScrollableLayerGuid::ViewID& aScrollId) {
+  if (!mUIThread->IsOnCurrentThread()) {
+    mUIThread->Dispatch(NewRunnableMethod<ScrollableLayerGuid::ViewID>(
+        "layers::ChromeProcessController::NotifyAsyncScrollbarDragRejected",
+        this, &ChromeProcessController::NotifyAsyncScrollbarDragRejected,
+        aScrollId));
+    return;
+  }
+
+  APZCCallbackHelper::NotifyAsyncScrollbarDragRejected(aScrollId);
+}
+
+void ChromeProcessController::NotifyAsyncAutoscrollRejected(
+    const ScrollableLayerGuid::ViewID& aScrollId) {
+  if (!mUIThread->IsOnCurrentThread()) {
+    mUIThread->Dispatch(NewRunnableMethod<ScrollableLayerGuid::ViewID>(
+        "layers::ChromeProcessController::NotifyAsyncAutoscrollRejected", this,
+        &ChromeProcessController::NotifyAsyncAutoscrollRejected, aScrollId));
+    return;
+  }
+
+  APZCCallbackHelper::NotifyAsyncAutoscrollRejected(aScrollId);
+}
+
+void ChromeProcessController::CancelAutoscroll(
+    const ScrollableLayerGuid& aGuid) {
+  if (!mUIThread->IsOnCurrentThread()) {
+    mUIThread->Dispatch(NewRunnableMethod<ScrollableLayerGuid>(
+        "layers::ChromeProcessController::CancelAutoscroll", this,
+        &ChromeProcessController::CancelAutoscroll, aGuid));
+    return;
+  }
+
+  APZCCallbackHelper::CancelAutoscroll(aGuid.mScrollId);
+}
diff --git a/gfx/layers/apz/util/ChromeProcessController.h b/gfx/layers/apz/util/ChromeProcessController.h
new file mode 100644
index 0000000000..158a0d6eba
--- /dev/null
+++ b/gfx/layers/apz/util/ChromeProcessController.h
@@ -0,0 +1,97 @@
+/* -*- 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 mozilla_layers_ChromeProcessController_h
+#define mozilla_layers_ChromeProcessController_h
+
+#include "mozilla/layers/GeckoContentController.h"
+#include "nsCOMPtr.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/layers/MatrixMessage.h"
+
+class nsIDOMWindowUtils;
+class nsISerialEventTarget;
+class nsIWidget;
+
+namespace mozilla {
+class PresShell;
+namespace dom {
+class Document;
+}
+
+namespace layers {
+
+class IAPZCTreeManager;
+class APZEventState;
+
+/**
+ * ChromeProcessController is a GeckoContentController attached to the root of
+ * a compositor's layer tree. It's used directly by APZ by default, and remoted
+ * using PAPZ if there is a gpu process.
+ *
+ * If ChromeProcessController needs to implement a new method on
+ * GeckoContentController PAPZ, APZChild, and RemoteContentController must be
+ * updated to handle it.
+ */
+class ChromeProcessController : public mozilla::layers::GeckoContentController {
+ protected:
+  typedef mozilla::layers::FrameMetrics FrameMetrics;
+  typedef mozilla::layers::ScrollableLayerGuid ScrollableLayerGuid;
+
+ public:
+  explicit ChromeProcessController(nsIWidget* aWidget,
+                                   APZEventState* aAPZEventState,
+                                   IAPZCTreeManager* aAPZCTreeManager);
+  virtual ~ChromeProcessController();
+  void Destroy() override;
+
+  // GeckoContentController interface
+  void NotifyLayerTransforms(nsTArray<MatrixMessage>&& aTransforms) override;
+  void RequestContentRepaint(const RepaintRequest& aRequest) override;
+  bool IsRepaintThread() override;
+  void DispatchToRepaintThread(already_AddRefed<Runnable> aTask) override;
+  MOZ_CAN_RUN_SCRIPT
+  void HandleTap(TapType aType, const mozilla::LayoutDevicePoint& aPoint,
+                 Modifiers aModifiers, const ScrollableLayerGuid& aGuid,
+                 uint64_t aInputBlockId) override;
+  void NotifyPinchGesture(PinchGestureInput::PinchGestureType aType,
+                          const ScrollableLayerGuid& aGuid,
+                          const LayoutDevicePoint& aFocusPoint,
+                          LayoutDeviceCoord aSpanChange,
+                          Modifiers aModifiers) override;
+  void NotifyAPZStateChange(const ScrollableLayerGuid& aGuid,
+                            APZStateChange aChange, int aArg) override;
+  void NotifyMozMouseScrollEvent(const ScrollableLayerGuid::ViewID& aScrollId,
+                                 const nsString& aEvent) override;
+  void NotifyFlushComplete() override;
+  void NotifyAsyncScrollbarDragInitiated(
+      uint64_t aDragBlockId, const ScrollableLayerGuid::ViewID& aScrollId,
+      ScrollDirection aDirection) override;
+  void NotifyAsyncScrollbarDragRejected(
+      const ScrollableLayerGuid::ViewID& aScrollId) override;
+  void NotifyAsyncAutoscrollRejected(
+      const ScrollableLayerGuid::ViewID& aScrollId) override;
+  void CancelAutoscroll(const ScrollableLayerGuid& aGuid) override;
+
+ private:
+  nsCOMPtr<nsIWidget> mWidget;
+  RefPtr<APZEventState> mAPZEventState;
+  RefPtr<IAPZCTreeManager> mAPZCTreeManager;
+  nsCOMPtr<nsISerialEventTarget> mUIThread;
+
+  void InitializeRoot();
+  PresShell* GetPresShell() const;
+  dom::Document* GetRootDocument() const;
+  dom::Document* GetRootContentDocument(
+      const ScrollableLayerGuid::ViewID& aScrollId) const;
+  void HandleDoubleTap(const mozilla::CSSPoint& aPoint, Modifiers aModifiers,
+                       const ScrollableLayerGuid& aGuid);
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /* mozilla_layers_ChromeProcessController_h */
diff --git a/gfx/layers/apz/util/ContentProcessController.cpp b/gfx/layers/apz/util/ContentProcessController.cpp
new file mode 100644
index 0000000000..0c52890631
--- /dev/null
+++ b/gfx/layers/apz/util/ContentProcessController.cpp
@@ -0,0 +1,108 @@
+/* -*- 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 "ContentProcessController.h"
+
+#include "mozilla/PresShell.h"
+#include "mozilla/dom/BrowserChild.h"
+#include "mozilla/layers/APZCCallbackHelper.h"
+#include "mozilla/layers/APZChild.h"
+#include "nsIContentInlines.h"
+
+#include "InputData.h"  // for InputData
+
+namespace mozilla {
+namespace layers {
+
+ContentProcessController::ContentProcessController(
+    const RefPtr<dom::BrowserChild>& aBrowser)
+    : mBrowser(aBrowser) {
+  MOZ_ASSERT(mBrowser);
+}
+
+void ContentProcessController::NotifyLayerTransforms(
+    nsTArray<MatrixMessage>&& aTransforms) {
+  // This should never get called
+  MOZ_ASSERT(false);
+}
+
+void ContentProcessController::RequestContentRepaint(
+    const RepaintRequest& aRequest) {
+  if (mBrowser) {
+    mBrowser->UpdateFrame(aRequest);
+  }
+}
+
+void ContentProcessController::HandleTap(TapType aType,
+                                         const LayoutDevicePoint& aPoint,
+                                         Modifiers aModifiers,
+                                         const ScrollableLayerGuid& aGuid,
+                                         uint64_t aInputBlockId) {
+  // This should never get called
+  MOZ_ASSERT(false);
+}
+
+void ContentProcessController::NotifyPinchGesture(
+    PinchGestureInput::PinchGestureType aType, const ScrollableLayerGuid& aGuid,
+    const LayoutDevicePoint& aFocusPoint, LayoutDeviceCoord aSpanChange,
+    Modifiers aModifiers) {
+  // This should never get called
+  MOZ_ASSERT_UNREACHABLE("Unexpected message to content process");
+}
+
+void ContentProcessController::NotifyAPZStateChange(
+    const ScrollableLayerGuid& aGuid, APZStateChange aChange, int aArg) {
+  if (mBrowser) {
+    mBrowser->NotifyAPZStateChange(aGuid.mScrollId, aChange, aArg);
+  }
+}
+
+void ContentProcessController::NotifyMozMouseScrollEvent(
+    const ScrollableLayerGuid::ViewID& aScrollId, const nsString& aEvent) {
+  if (mBrowser) {
+    APZCCallbackHelper::NotifyMozMouseScrollEvent(aScrollId, aEvent);
+  }
+}
+
+void ContentProcessController::NotifyFlushComplete() {
+  if (mBrowser) {
+    RefPtr<PresShell> presShell = mBrowser->GetTopLevelPresShell();
+    APZCCallbackHelper::NotifyFlushComplete(presShell);
+  }
+}
+
+void ContentProcessController::NotifyAsyncScrollbarDragInitiated(
+    uint64_t aDragBlockId, const ScrollableLayerGuid::ViewID& aScrollId,
+    ScrollDirection aDirection) {
+  APZCCallbackHelper::NotifyAsyncScrollbarDragInitiated(aDragBlockId, aScrollId,
+                                                        aDirection);
+}
+
+void ContentProcessController::NotifyAsyncScrollbarDragRejected(
+    const ScrollableLayerGuid::ViewID& aScrollId) {
+  APZCCallbackHelper::NotifyAsyncScrollbarDragRejected(aScrollId);
+}
+
+void ContentProcessController::NotifyAsyncAutoscrollRejected(
+    const ScrollableLayerGuid::ViewID& aScrollId) {
+  APZCCallbackHelper::NotifyAsyncAutoscrollRejected(aScrollId);
+}
+
+void ContentProcessController::CancelAutoscroll(
+    const ScrollableLayerGuid& aGuid) {
+  // This should never get called
+  MOZ_ASSERT_UNREACHABLE("Unexpected message to content process");
+}
+
+bool ContentProcessController::IsRepaintThread() { return NS_IsMainThread(); }
+
+void ContentProcessController::DispatchToRepaintThread(
+    already_AddRefed<Runnable> aTask) {
+  NS_DispatchToMainThread(std::move(aTask));
+}
+
+}  // namespace layers
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/ContentProcessController.h b/gfx/layers/apz/util/ContentProcessController.h
new file mode 100644
index 0000000000..ab5522cd44
--- /dev/null
+++ b/gfx/layers/apz/util/ContentProcessController.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 mozilla_layers_ContentProcessController_h
+#define mozilla_layers_ContentProcessController_h
+
+#include "mozilla/layers/GeckoContentController.h"
+
+class nsIObserver;
+
+namespace mozilla {
+
+namespace dom {
+class BrowserChild;
+}  // namespace dom
+
+namespace layers {
+
+class APZChild;
+
+/**
+ * ContentProcessController is a GeckoContentController for a BrowserChild, and
+ * is always remoted using PAPZ/APZChild.
+ *
+ * ContentProcessController is created in ContentChild when a layer tree id has
+ * been allocated for a PBrowser that lives in that content process, and is
+ * destroyed when the Destroy message is received, or when the tab dies.
+ *
+ * If ContentProcessController needs to implement a new method on
+ * GeckoContentController PAPZ, APZChild, and RemoteContentController must be
+ * updated to handle it.
+ */
+class ContentProcessController final : public GeckoContentController {
+ public:
+  explicit ContentProcessController(const RefPtr<dom::BrowserChild>& aBrowser);
+
+  // GeckoContentController
+
+  void NotifyLayerTransforms(nsTArray<MatrixMessage>&& aTransforms) override;
+
+  void RequestContentRepaint(const RepaintRequest& aRequest) override;
+
+  void HandleTap(TapType aType, const LayoutDevicePoint& aPoint,
+                 Modifiers aModifiers, const ScrollableLayerGuid& aGuid,
+                 uint64_t aInputBlockId) override;
+
+  void NotifyPinchGesture(PinchGestureInput::PinchGestureType aType,
+                          const ScrollableLayerGuid& aGuid,
+                          const LayoutDevicePoint& aFocusPoint,
+                          LayoutDeviceCoord aSpanChange,
+                          Modifiers aModifiers) override;
+
+  void NotifyAPZStateChange(const ScrollableLayerGuid& aGuid,
+                            APZStateChange aChange, int aArg) override;
+
+  void NotifyMozMouseScrollEvent(const ScrollableLayerGuid::ViewID& aScrollId,
+                                 const nsString& aEvent) override;
+
+  void NotifyFlushComplete() override;
+
+  void NotifyAsyncScrollbarDragInitiated(
+      uint64_t aDragBlockId, const ScrollableLayerGuid::ViewID& aScrollId,
+      ScrollDirection aDirection) override;
+  void NotifyAsyncScrollbarDragRejected(
+      const ScrollableLayerGuid::ViewID& aScrollId) override;
+
+  void NotifyAsyncAutoscrollRejected(
+      const ScrollableLayerGuid::ViewID& aScrollId) override;
+
+  void CancelAutoscroll(const ScrollableLayerGuid& aGuid) override;
+
+  bool IsRepaintThread() override;
+
+  void DispatchToRepaintThread(already_AddRefed<Runnable> aTask) override;
+
+ private:
+  RefPtr<dom::BrowserChild> mBrowser;
+};
+
+}  // namespace layers
+
+}  // namespace mozilla
+
+#endif  // mozilla_layers_ContentProcessController_h
diff --git a/gfx/layers/apz/util/DoubleTapToZoom.cpp b/gfx/layers/apz/util/DoubleTapToZoom.cpp
new file mode 100644
index 0000000000..6d4d3d7f0c
--- /dev/null
+++ b/gfx/layers/apz/util/DoubleTapToZoom.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 "DoubleTapToZoom.h"
+
+#include <algorithm>  // for std::min, std::max
+
+#include "mozilla/PresShell.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/dom/Element.h"
+#include "nsCOMPtr.h"
+#include "nsIContent.h"
+#include "mozilla/dom/Document.h"
+#include "nsIFrame.h"
+#include "nsIFrameInlines.h"
+#include "nsIScrollableFrame.h"
+#include "nsLayoutUtils.h"
+#include "nsStyleConsts.h"
+
+namespace mozilla {
+namespace layers {
+
+namespace {
+
+using FrameForPointOption = nsLayoutUtils::FrameForPointOption;
+
+// Returns the DOM element found at |aPoint|, interpreted as being relative to
+// the root frame of |aPresShell| in visual coordinates. If the point is inside
+// a subdocument, returns an element inside the subdocument, rather than the
+// subdocument element (and does so recursively). The implementation was adapted
+// from DocumentOrShadowRoot::ElementFromPoint(), with the notable exception
+// that we don't pass nsLayoutUtils::IGNORE_CROSS_DOC to GetFrameForPoint(), so
+// as to get the behaviour described above in the presence of subdocuments.
+static already_AddRefed<dom::Element> ElementFromPoint(
+    const RefPtr<PresShell>& aPresShell, const CSSPoint& aPoint) {
+  nsIFrame* rootFrame = aPresShell->GetRootFrame();
+  if (!rootFrame) {
+    return nullptr;
+  }
+  nsIFrame* frame = nsLayoutUtils::GetFrameForPoint(
+      RelativeTo{rootFrame, ViewportType::Visual}, CSSPoint::ToAppUnits(aPoint),
+      {{FrameForPointOption::IgnorePaintSuppression}});
+  while (frame && (!frame->GetContent() ||
+                   frame->GetContent()->IsInNativeAnonymousSubtree())) {
+    frame = nsLayoutUtils::GetParentOrPlaceholderFor(frame);
+  }
+  if (!frame) {
+    return nullptr;
+  }
+  // FIXME(emilio): This should probably use the flattened tree, GetParent() is
+  // not guaranteed to be an element in presence of shadow DOM.
+  nsIContent* content = frame->GetContent();
+  if (!content) {
+    return nullptr;
+  }
+  if (dom::Element* element = content->GetAsElementOrParentElement()) {
+    return do_AddRef(element);
+  }
+  return nullptr;
+}
+
+static bool ShouldZoomToElement(const nsCOMPtr<dom::Element>& aElement) {
+  if (nsIFrame* frame = aElement->GetPrimaryFrame()) {
+    if (frame->StyleDisplay()->IsInlineFlow()) {
+      return false;
+    }
+  }
+  if (aElement->IsAnyOfHTMLElements(nsGkAtoms::li, nsGkAtoms::q)) {
+    return false;
+  }
+  return true;
+}
+
+static bool IsRectZoomedIn(const CSSRect& aRect,
+                           const CSSRect& aCompositedArea) {
+  // This functions checks to see if the area of the rect visible in the
+  // composition bounds (i.e. the overlapArea variable below) is approximately
+  // the max area of the rect we can show.
+  CSSRect overlap = aCompositedArea.Intersect(aRect);
+  float overlapArea = overlap.Width() * overlap.Height();
+  float availHeight = std::min(
+      aRect.Width() * aCompositedArea.Height() / aCompositedArea.Width(),
+      aRect.Height());
+  float showing = overlapArea / (aRect.Width() * availHeight);
+  float ratioW = aRect.Width() / aCompositedArea.Width();
+  float ratioH = aRect.Height() / aCompositedArea.Height();
+
+  return showing > 0.9 && (ratioW > 0.9 || ratioH > 0.9);
+}
+
+}  // namespace
+
+CSSRect CalculateRectToZoomTo(const RefPtr<dom::Document>& aRootContentDocument,
+                              const CSSPoint& aPoint) {
+  // Ensure the layout information we get is up-to-date.
+  aRootContentDocument->FlushPendingNotifications(FlushType::Layout);
+
+  // An empty rect as return value is interpreted as "zoom out".
+  const CSSRect zoomOut;
+
+  RefPtr<PresShell> presShell = aRootContentDocument->GetPresShell();
+  if (!presShell) {
+    return zoomOut;
+  }
+
+  nsIScrollableFrame* rootScrollFrame =
+      presShell->GetRootScrollFrameAsScrollable();
+  if (!rootScrollFrame) {
+    return zoomOut;
+  }
+
+  nsCOMPtr<dom::Element> element = ElementFromPoint(presShell, aPoint);
+  if (!element) {
+    return zoomOut;
+  }
+
+  while (element && !ShouldZoomToElement(element)) {
+    element = element->GetParentElement();
+  }
+
+  if (!element) {
+    return zoomOut;
+  }
+
+  FrameMetrics metrics =
+      nsLayoutUtils::CalculateBasicFrameMetrics(rootScrollFrame);
+  CSSPoint visualScrollOffset = metrics.GetVisualScrollOffset();
+  CSSRect compositedArea(visualScrollOffset,
+                         metrics.CalculateCompositedSizeInCssPixels());
+  const CSSCoord margin = 15;
+  CSSRect rect =
+      nsLayoutUtils::GetBoundingContentRect(element, rootScrollFrame);
+
+  // If the element is taller than the visible area of the page scale
+  // the height of the |rect| so that it has the same aspect ratio as
+  // the root frame.  The clipped |rect| is centered on the y value of
+  // the touch point. This allows tall narrow elements to be zoomed.
+  if (!rect.IsEmpty() && compositedArea.Width() > 0.0f) {
+    const float widthRatio = rect.Width() / compositedArea.Width();
+    float targetHeight = compositedArea.Height() * widthRatio;
+    if (widthRatio < 0.9 && targetHeight < rect.Height()) {
+      const CSSPoint scrollPoint =
+          CSSPoint::FromAppUnits(rootScrollFrame->GetScrollPosition());
+      float newY = aPoint.y + scrollPoint.y - (targetHeight * 0.5f);
+      if ((newY + targetHeight) > rect.YMost()) {
+        rect.MoveByY(rect.Height() - targetHeight);
+      } else if (newY > rect.Y()) {
+        rect.MoveToY(newY);
+      }
+      rect.SetHeight(targetHeight);
+    }
+  }
+
+  rect = CSSRect(std::max(metrics.GetScrollableRect().X(), rect.X() - margin),
+                 rect.Y(), rect.Width() + 2 * margin, rect.Height());
+  // Constrict the rect to the screen's right edge
+  rect.SetWidth(
+      std::min(rect.Width(), metrics.GetScrollableRect().XMost() - rect.X()));
+
+  // If the rect is already taking up most of the visible area and is
+  // stretching the width of the page, then we want to zoom out instead.
+  if (IsRectZoomedIn(rect, compositedArea)) {
+    return zoomOut;
+  }
+
+  CSSRect rounded(rect);
+  rounded.Round();
+
+  // If the block we're zooming to is really tall, and the user double-tapped
+  // more than a screenful of height from the top of it, then adjust the
+  // y-coordinate so that we center the actual point the user double-tapped
+  // upon. This prevents flying to the top of the page when double-tapping
+  // to zoom in (bug 761721). The 1.2 multiplier is just a little fuzz to
+  // compensate for 'rect' including horizontal margins but not vertical ones.
+  CSSCoord cssTapY = visualScrollOffset.y + aPoint.y;
+  if ((rect.Height() > rounded.Height()) &&
+      (cssTapY > rounded.Y() + (rounded.Height() * 1.2))) {
+    rounded.MoveToY(cssTapY - (rounded.Height() / 2));
+  }
+
+  return rounded;
+}
+
+}  // namespace layers
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/DoubleTapToZoom.h b/gfx/layers/apz/util/DoubleTapToZoom.h
new file mode 100644
index 0000000000..163481fe03
--- /dev/null
+++ b/gfx/layers/apz/util/DoubleTapToZoom.h
@@ -0,0 +1,35 @@
+/* -*- 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 mozilla_layers_DoubleTapToZoom_h
+#define mozilla_layers_DoubleTapToZoom_h
+
+#include "Units.h"
+
+template <class T>
+class RefPtr;
+
+namespace mozilla {
+namespace dom {
+class Document;
+}
+
+namespace layers {
+
+/**
+ * For a double tap at |aPoint|, return the rect to which the browser
+ * should zoom in response, or an empty rect if the browser should zoom out.
+ * |aDocument| should be the root content document for the content that was
+ * tapped.
+ */
+CSSRect CalculateRectToZoomTo(
+    const RefPtr<mozilla::dom::Document>& aRootContentDocument,
+    const CSSPoint& aPoint);
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /* mozilla_layers_DoubleTapToZoom_h */
diff --git a/gfx/layers/apz/util/InputAPZContext.cpp b/gfx/layers/apz/util/InputAPZContext.cpp
new file mode 100644
index 0000000000..77573221ff
--- /dev/null
+++ b/gfx/layers/apz/util/InputAPZContext.cpp
@@ -0,0 +1,65 @@
+/* -*- 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 "InputAPZContext.h"
+
+namespace mozilla {
+namespace layers {
+
+ScrollableLayerGuid InputAPZContext::sGuid;
+uint64_t InputAPZContext::sBlockId = 0;
+nsEventStatus InputAPZContext::sApzResponse = nsEventStatus_eSentinel;
+bool InputAPZContext::sPendingLayerization = false;
+bool InputAPZContext::sRoutedToChildProcess = false;
+
+/*static*/
+ScrollableLayerGuid InputAPZContext::GetTargetLayerGuid() { return sGuid; }
+
+/*static*/
+uint64_t InputAPZContext::GetInputBlockId() { return sBlockId; }
+
+/*static*/
+nsEventStatus InputAPZContext::GetApzResponse() { return sApzResponse; }
+
+/*static*/
+bool InputAPZContext::HavePendingLayerization() { return sPendingLayerization; }
+
+/*static*/
+bool InputAPZContext::WasRoutedToChildProcess() {
+  return sRoutedToChildProcess;
+}
+
+InputAPZContext::InputAPZContext(const ScrollableLayerGuid& aGuid,
+                                 const uint64_t& aBlockId,
+                                 const nsEventStatus& aApzResponse,
+                                 bool aPendingLayerization)
+    : mOldGuid(sGuid),
+      mOldBlockId(sBlockId),
+      mOldApzResponse(sApzResponse),
+      mOldPendingLayerization(sPendingLayerization),
+      mOldRoutedToChildProcess(sRoutedToChildProcess) {
+  sGuid = aGuid;
+  sBlockId = aBlockId;
+  sApzResponse = aApzResponse;
+  sPendingLayerization = aPendingLayerization;
+  sRoutedToChildProcess = false;
+}
+
+InputAPZContext::~InputAPZContext() {
+  sGuid = mOldGuid;
+  sBlockId = mOldBlockId;
+  sApzResponse = mOldApzResponse;
+  sPendingLayerization = mOldPendingLayerization;
+  sRoutedToChildProcess = mOldRoutedToChildProcess;
+}
+
+/*static*/
+void InputAPZContext::SetRoutedToChildProcess() {
+  sRoutedToChildProcess = true;
+}
+
+}  // namespace layers
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/InputAPZContext.h b/gfx/layers/apz/util/InputAPZContext.h
new file mode 100644
index 0000000000..928359ab1d
--- /dev/null
+++ b/gfx/layers/apz/util/InputAPZContext.h
@@ -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/. */
+
+#ifndef mozilla_layers_InputAPZContext_h
+#define mozilla_layers_InputAPZContext_h
+
+#include "mozilla/EventForwards.h"
+#include "mozilla/layers/ScrollableLayerGuid.h"
+
+namespace mozilla {
+namespace layers {
+
+// InputAPZContext is used to communicate various pieces of information
+// around the codebase without having to plumb it through lots of functions
+// and codepaths. Conceptually it is attached to a WidgetInputEvent that is
+// relevant to APZ.
+//
+// There are two types of information bits propagated using this class. One
+// type is propagated "downwards" (from a process entry point like nsBaseWidget
+// or BrowserChild) into deeper code that is run during complicated operations
+// like event dispatch. The other type is information that is propagated
+// "upwards", from the deeper code back to the entry point.
+class MOZ_STACK_CLASS InputAPZContext {
+ private:
+  // State that is propagated downwards from InputAPZContext creation into
+  // "deeper" code.
+  static ScrollableLayerGuid sGuid;
+  static uint64_t sBlockId;
+  static nsEventStatus sApzResponse;
+  static bool sPendingLayerization;
+
+  // State that is set in deeper code and propagated upwards.
+  static bool sRoutedToChildProcess;
+
+ public:
+  // Functions to access downwards-propagated data
+  static ScrollableLayerGuid GetTargetLayerGuid();
+  static uint64_t GetInputBlockId();
+  static nsEventStatus GetApzResponse();
+  static bool HavePendingLayerization();
+
+  // Functions to access upwards-propagated data
+  static bool WasRoutedToChildProcess();
+
+  // Constructor sets the data to be propagated downwards
+  InputAPZContext(const ScrollableLayerGuid& aGuid, const uint64_t& aBlockId,
+                  const nsEventStatus& aApzResponse,
+                  bool aPendingLayerization = false);
+  ~InputAPZContext();
+
+  // Functions to set data to be propagated upwards
+  static void SetRoutedToChildProcess();
+
+ private:
+  ScrollableLayerGuid mOldGuid;
+  uint64_t mOldBlockId;
+  nsEventStatus mOldApzResponse;
+  bool mOldPendingLayerization;
+
+  bool mOldRoutedToChildProcess;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /* mozilla_layers_InputAPZContext_h */
diff --git a/gfx/layers/apz/util/ScrollInputMethods.h b/gfx/layers/apz/util/ScrollInputMethods.h
new file mode 100644
index 0000000000..999f2c6abf
--- /dev/null
+++ b/gfx/layers/apz/util/ScrollInputMethods.h
@@ -0,0 +1,78 @@
+/* -*- 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 mozilla_layers_ScrollInputMethods_h
+#define mozilla_layers_ScrollInputMethods_h
+
+namespace mozilla {
+namespace layers {
+
+/**
+ * An enumeration that lists various input methods used to trigger scrolling.
+ * Used as the values for the SCROLL_INPUT_METHODS telemetry histogram.
+ */
+enum class ScrollInputMethod {
+
+  // === Driven by APZ ===
+
+  ApzTouch,          // touch events
+  ApzWheelPixel,     // wheel events, pixel scrolling mode
+  ApzWheelLine,      // wheel events, line scrolling mode
+  ApzWheelPage,      // wheel events, page scrolling mode
+  ApzPanGesture,     // pan gesture events (generally triggered by trackpad)
+  ApzScrollbarDrag,  // dragging the scrollbar
+
+  // === Driven by the main thread ===
+
+  // Keyboard
+  MainThreadScrollLine,       // line scrolling
+                              // (generally triggered by up/down arrow keys)
+  MainThreadScrollCharacter,  // character scrolling
+                              // (generally triggered by left/right arrow keys)
+  MainThreadScrollPage,       // page scrolling
+                              // (generally triggered by PageUp/PageDown keys)
+  MainThreadCompleteScroll,   // scrolling to the end of the scroll range
+                              // (generally triggered by Home/End keys)
+  MainThreadScrollCaretIntoView,  // scrolling to bring the caret into view
+                                  // after moving the caret via the keyboard
+
+  // Touch
+  MainThreadTouch,  // touch events
+
+  // Scrollbar
+  MainThreadScrollbarDrag,         // dragging the scrollbar
+  MainThreadScrollbarButtonClick,  // clicking the buttons at the ends of the
+                                   // scrollback track
+  MainThreadScrollbarTrackClick,   // clicking the scrollbar track above or
+                                   // below the thumb
+
+  // Autoscrolling
+  MainThreadAutoscrolling,  // autoscrolling
+
+  // === Additional input methods implemented in APZ ===
+
+  // Async Keyboard
+  ApzScrollLine,       // line scrolling
+                       // (generally triggered by up/down arrow keys)
+  ApzScrollCharacter,  // character scrolling
+                       // (generally triggered by left/right arrow keys)
+  ApzScrollPage,       // page scrolling
+                       // (generally triggered by PageUp/PageDown keys)
+  ApzCompleteScroll,   // scrolling to the end of the scroll range
+                       // (generally triggered by Home/End keys)
+
+  // Autoscrolling
+  ApzAutoscrolling,
+
+  // New input methods can be added at the end, up to a maximum of 64.
+  // They should only be added at the end, to preserve the numerical values
+  // of the existing enumerators.
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /* mozilla_layers_ScrollInputMethods_h */
diff --git a/gfx/layers/apz/util/ScrollLinkedEffectDetector.cpp b/gfx/layers/apz/util/ScrollLinkedEffectDetector.cpp
new file mode 100644
index 0000000000..6ef8749a9c
--- /dev/null
+++ b/gfx/layers/apz/util/ScrollLinkedEffectDetector.cpp
@@ -0,0 +1,47 @@
+/* -*- 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 "ScrollLinkedEffectDetector.h"
+
+#include "mozilla/dom/Document.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla {
+namespace layers {
+
+uint32_t ScrollLinkedEffectDetector::sDepth = 0;
+bool ScrollLinkedEffectDetector::sFoundScrollLinkedEffect = false;
+
+/* static */
+void ScrollLinkedEffectDetector::PositioningPropertyMutated() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (sDepth > 0) {
+    // We are inside a scroll event dispatch
+    sFoundScrollLinkedEffect = true;
+  }
+}
+
+ScrollLinkedEffectDetector::ScrollLinkedEffectDetector(dom::Document* aDoc)
+    : mDocument(aDoc) {
+  MOZ_ASSERT(NS_IsMainThread());
+  sDepth++;
+}
+
+ScrollLinkedEffectDetector::~ScrollLinkedEffectDetector() {
+  sDepth--;
+  if (sDepth == 0) {
+    // We have exited all (possibly-nested) scroll event dispatches,
+    // record whether or not we found an effect, and reset state
+    if (sFoundScrollLinkedEffect) {
+      mDocument->ReportHasScrollLinkedEffect();
+      sFoundScrollLinkedEffect = false;
+    }
+  }
+}
+
+}  // namespace layers
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/ScrollLinkedEffectDetector.h b/gfx/layers/apz/util/ScrollLinkedEffectDetector.h
new file mode 100644
index 0000000000..81044ed614
--- /dev/null
+++ b/gfx/layers/apz/util/ScrollLinkedEffectDetector.h
@@ -0,0 +1,46 @@
+/* -*- 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 mozilla_layers_ScrollLinkedEffectDetector_h
+#define mozilla_layers_ScrollLinkedEffectDetector_h
+
+#include "mozilla/RefPtr.h"
+
+namespace mozilla {
+
+namespace dom {
+class Document;
+}
+
+namespace layers {
+
+// ScrollLinkedEffectDetector is used to detect the existence of a scroll-linked
+// effect on a webpage. Generally speaking, a scroll-linked effect is something
+// on the page that animates or changes with respect to the scroll position.
+// Content authors usually rely on running some JS in response to the scroll
+// event in order to implement such effects, and therefore it tends to be laggy
+// or work improperly with APZ enabled. This class helps us detect such an
+// effect so that we can warn the author and/or take other preventative
+// measures.
+class MOZ_STACK_CLASS ScrollLinkedEffectDetector final {
+ private:
+  static uint32_t sDepth;
+  static bool sFoundScrollLinkedEffect;
+
+ public:
+  static void PositioningPropertyMutated();
+
+  explicit ScrollLinkedEffectDetector(dom::Document*);
+  ~ScrollLinkedEffectDetector();
+
+ private:
+  RefPtr<dom::Document> mDocument;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /* mozilla_layers_ScrollLinkedEffectDetector_h */
diff --git a/gfx/layers/apz/util/TouchActionHelper.cpp b/gfx/layers/apz/util/TouchActionHelper.cpp
new file mode 100644
index 0000000000..1cac71467f
--- /dev/null
+++ b/gfx/layers/apz/util/TouchActionHelper.cpp
@@ -0,0 +1,106 @@
+/* -*- 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 "TouchActionHelper.h"
+
+#include "mozilla/layers/IAPZCTreeManager.h"
+#include "nsContainerFrame.h"
+#include "nsIFrameInlines.h"
+#include "nsIScrollableFrame.h"
+#include "nsLayoutUtils.h"
+
+namespace mozilla {
+namespace layers {
+
+static void UpdateAllowedBehavior(StyleTouchAction aTouchActionValue,
+                                  bool aConsiderPanning,
+                                  TouchBehaviorFlags& aOutBehavior) {
+  if (aTouchActionValue != StyleTouchAction::AUTO) {
+    // Double-tap-zooming need property value AUTO
+    aOutBehavior &= ~AllowedTouchBehavior::DOUBLE_TAP_ZOOM;
+    if (aTouchActionValue != StyleTouchAction::MANIPULATION &&
+        !(aTouchActionValue & StyleTouchAction::PINCH_ZOOM)) {
+      // Pinch-zooming needs value AUTO or MANIPULATION, or the PINCH_ZOOM bit
+      // set
+      aOutBehavior &= ~AllowedTouchBehavior::PINCH_ZOOM;
+    }
+  }
+
+  if (aConsiderPanning) {
+    if (aTouchActionValue == StyleTouchAction::NONE) {
+      aOutBehavior &= ~AllowedTouchBehavior::VERTICAL_PAN;
+      aOutBehavior &= ~AllowedTouchBehavior::HORIZONTAL_PAN;
+    }
+
+    // Values pan-x and pan-y set at the same time to the same element do not
+    // affect panning constraints. Therefore we need to check whether pan-x is
+    // set without pan-y and the same for pan-y.
+    if ((aTouchActionValue & StyleTouchAction::PAN_X) &&
+        !(aTouchActionValue & StyleTouchAction::PAN_Y)) {
+      aOutBehavior &= ~AllowedTouchBehavior::VERTICAL_PAN;
+    } else if ((aTouchActionValue & StyleTouchAction::PAN_Y) &&
+               !(aTouchActionValue & StyleTouchAction::PAN_X)) {
+      aOutBehavior &= ~AllowedTouchBehavior::HORIZONTAL_PAN;
+    }
+  }
+}
+
+TouchBehaviorFlags TouchActionHelper::GetAllowedTouchBehavior(
+    nsIWidget* aWidget, RelativeTo aRootFrame,
+    const LayoutDeviceIntPoint& aPoint) {
+  TouchBehaviorFlags behavior = AllowedTouchBehavior::VERTICAL_PAN |
+                                AllowedTouchBehavior::HORIZONTAL_PAN |
+                                AllowedTouchBehavior::PINCH_ZOOM |
+                                AllowedTouchBehavior::DOUBLE_TAP_ZOOM;
+
+  nsPoint relativePoint =
+      nsLayoutUtils::GetEventCoordinatesRelativeTo(aWidget, aPoint, aRootFrame);
+
+  nsIFrame* target = nsLayoutUtils::GetFrameForPoint(aRootFrame, relativePoint);
+  if (!target) {
+    return behavior;
+  }
+  nsIScrollableFrame* nearestScrollableParent =
+      nsLayoutUtils::GetNearestScrollableFrame(target, 0);
+  nsIFrame* nearestScrollableFrame = do_QueryFrame(nearestScrollableParent);
+
+  // We're walking up the DOM tree until we meet the element with touch behavior
+  // and accumulating touch-action restrictions of all elements in this chain.
+  // The exact quote from the spec, that clarifies more:
+  // To determine the effect of a touch, find the nearest ancestor (starting
+  // from the element itself) that has a default touch behavior. Then examine
+  // the touch-action property of each element between the hit tested element
+  // and the element with the default touch behavior (including both the hit
+  // tested element and the element with the default touch behavior). If the
+  // touch-action property of any of those elements disallows the default touch
+  // behavior, do nothing. Otherwise allow the element to start considering the
+  // touch for the purposes of executing a default touch behavior.
+
+  // Currently we support only two touch behaviors: panning and zooming.
+  // For panning we walk up until we meet the first scrollable element (the
+  // element that supports panning) or root element. For zooming we walk up
+  // until the root element since Firefox currently supports only zooming of the
+  // root frame but not the subframes.
+
+  bool considerPanning = true;
+
+  for (nsIFrame* frame = target; frame && frame->GetContent() && behavior;
+       frame = frame->GetInFlowParent()) {
+    UpdateAllowedBehavior(nsLayoutUtils::GetTouchActionFromFrame(frame),
+                          considerPanning, behavior);
+
+    if (frame == nearestScrollableFrame) {
+      // We met the scrollable element, after it we shouldn't consider
+      // touch-action values for the purpose of panning but only for zooming.
+      considerPanning = false;
+    }
+  }
+
+  return behavior;
+}
+
+}  // namespace layers
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/TouchActionHelper.h b/gfx/layers/apz/util/TouchActionHelper.h
new file mode 100644
index 0000000000..723b276997
--- /dev/null
+++ b/gfx/layers/apz/util/TouchActionHelper.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 __mozilla_layers_TouchActionHelper_h__
+#define __mozilla_layers_TouchActionHelper_h__
+
+#include "mozilla/layers/LayersTypes.h"  // for TouchBehaviorFlags
+#include "RelativeTo.h"                  // for RelativeTo
+
+class nsIFrame;
+class nsIWidget;
+
+namespace mozilla {
+namespace layers {
+
+/*
+ * Helper class to figure out the allowed touch behavior for frames, as per
+ * the touch-action spec.
+ */
+class TouchActionHelper {
+ public:
+  /*
+   * Performs hit testing on content, finds frame that corresponds to the aPoint
+   * and retrieves touch-action css property value from it according the rules
+   * specified in the spec:
+   * http://www.w3.org/TR/pointerevents/#the-touch-action-css-property.
+   */
+  static TouchBehaviorFlags GetAllowedTouchBehavior(
+      nsIWidget* aWidget, RelativeTo aRootFrame,
+      const LayoutDeviceIntPoint& aPoint);
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /*__mozilla_layers_TouchActionHelper_h__ */
diff --git a/gfx/layers/apz/util/TouchCounter.cpp b/gfx/layers/apz/util/TouchCounter.cpp
new file mode 100644
index 0000000000..9e4d6f1ba6
--- /dev/null
+++ b/gfx/layers/apz/util/TouchCounter.cpp
@@ -0,0 +1,74 @@
+/* -*- 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 "TouchCounter.h"
+
+#include "InputData.h"
+#include "mozilla/TouchEvents.h"
+
+namespace mozilla {
+namespace layers {
+
+TouchCounter::TouchCounter() : mActiveTouchCount(0) {}
+
+void TouchCounter::Update(const MultiTouchInput& aInput) {
+  switch (aInput.mType) {
+    case MultiTouchInput::MULTITOUCH_START:
+      // touch-start event contains all active touches of the current session
+      mActiveTouchCount = aInput.mTouches.Length();
+      break;
+    case MultiTouchInput::MULTITOUCH_END:
+      if (mActiveTouchCount >= aInput.mTouches.Length()) {
+        // touch-end event contains only released touches
+        mActiveTouchCount -= aInput.mTouches.Length();
+      } else {
+        NS_WARNING("Got an unexpected touchend");
+        mActiveTouchCount = 0;
+      }
+      break;
+    case MultiTouchInput::MULTITOUCH_CANCEL:
+      mActiveTouchCount = 0;
+      break;
+    case MultiTouchInput::MULTITOUCH_MOVE:
+      break;
+  }
+}
+
+void TouchCounter::Update(const WidgetTouchEvent& aEvent) {
+  switch (aEvent.mMessage) {
+    case eTouchStart:
+      // touch-start event contains all active touches of the current session
+      mActiveTouchCount = aEvent.mTouches.Length();
+      break;
+    case eTouchEnd: {
+      // touch-end contains all touches, but ones being lifted are marked as
+      // changed
+      uint32_t liftedTouches = 0;
+      for (const auto& touch : aEvent.mTouches) {
+        if (touch->mChanged) {
+          liftedTouches++;
+        }
+      }
+      if (mActiveTouchCount >= liftedTouches) {
+        mActiveTouchCount -= liftedTouches;
+      } else {
+        NS_WARNING("Got an unexpected touchend");
+        mActiveTouchCount = 0;
+      }
+      break;
+    }
+    case eTouchCancel:
+      mActiveTouchCount = 0;
+      break;
+    default:
+      break;
+  }
+}
+
+uint32_t TouchCounter::GetActiveTouchCount() const { return mActiveTouchCount; }
+
+}  // namespace layers
+}  // namespace mozilla
diff --git a/gfx/layers/apz/util/TouchCounter.h b/gfx/layers/apz/util/TouchCounter.h
new file mode 100644
index 0000000000..c13f475355
--- /dev/null
+++ b/gfx/layers/apz/util/TouchCounter.h
@@ -0,0 +1,36 @@
+/* -*- 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 mozilla_layers_TouchCounter_h
+#define mozilla_layers_TouchCounter_h
+
+#include "mozilla/EventForwards.h"
+
+namespace mozilla {
+
+class MultiTouchInput;
+
+namespace layers {
+
+// TouchCounter simply tracks the number of active touch points. Feed it
+// your input events to update the internal state. Generally you should
+// only be calling one of the Update functions, depending on which type
+// of touch inputs you have access to.
+class TouchCounter {
+ public:
+  TouchCounter();
+  void Update(const MultiTouchInput& aInput);
+  void Update(const WidgetTouchEvent& aEvent);
+  uint32_t GetActiveTouchCount() const;
+
+ private:
+  uint32_t mActiveTouchCount;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif /* mozilla_layers_TouchCounter_h */