1 files changed, 867 insertions, 0 deletions
diff --git a/dom/base/nsDOMMutationObserver.h b/dom/base/nsDOMMutationObserver.h
new file mode 100644
index 0000000000..92ab53d43a
--- /dev/null
+++ b/dom/base/nsDOMMutationObserver.h
@@ -0,0 +1,867 @@
+/* -*- 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 nsDOMMutationObserver_h
+#define nsDOMMutationObserver_h
+
+#include <utility>
+
+#include "mozilla/Attributes.h"
+#include "mozilla/dom/Animation.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/MutationEventBinding.h"
+#include "mozilla/dom/MutationObserverBinding.h"
+#include "mozilla/dom/Nullable.h"
+#include "nsCOMArray.h"
+#include "nsClassHashtable.h"
+#include "nsContentList.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsGlobalWindowInner.h"
+#include "nsIAnimationObserver.h"
+#include "nsPIDOMWindow.h"
+#include "nsStubAnimationObserver.h"
+#include "nsTArray.h"
+#include "nsWrapperCache.h"
+
+class nsIPrincipal;
+
+class nsDOMMutationObserver;
+using mozilla::dom::MutationObservingInfo;
+
+namespace mozilla::dom {
+class Element;
+}
+
+class nsDOMMutationRecord final : public nsISupports, public nsWrapperCache {
+  virtual ~nsDOMMutationRecord() = default;
+
+ public:
+  using AnimationArray = nsTArray<RefPtr<mozilla::dom::Animation>>;
+
+  nsDOMMutationRecord(nsAtom* aType, nsISupports* aOwner)
+      : mType(aType),
+        mAttrNamespace(VoidString()),
+        mPrevValue(VoidString()),
+        mOwner(aOwner) {}
+
+  nsISupports* GetParentObject() const { return mOwner; }
+
+  virtual JSObject* WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) override {
+    return mozilla::dom::MutationRecord_Binding::Wrap(aCx, this, aGivenProto);
+  }
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(nsDOMMutationRecord)
+
+  void GetType(mozilla::dom::DOMString& aRetVal) const {
+    aRetVal.SetKnownLiveAtom(mType, mozilla::dom::DOMString::eNullNotExpected);
+  }
+
+  nsINode* GetTarget() const { return mTarget; }
+
+  nsINodeList* AddedNodes();
+
+  nsINodeList* RemovedNodes();
+
+  nsINode* GetPreviousSibling() const { return mPreviousSibling; }
+
+  nsINode* GetNextSibling() const { return mNextSibling; }
+
+  void GetAttributeName(mozilla::dom::DOMString& aRetVal) const {
+    aRetVal.SetKnownLiveAtom(mAttrName,
+                             mozilla::dom::DOMString::eTreatNullAsNull);
+  }
+
+  void GetAttributeNamespace(mozilla::dom::DOMString& aRetVal) const {
+    aRetVal.SetKnownLiveString(mAttrNamespace);
+  }
+
+  void GetOldValue(mozilla::dom::DOMString& aRetVal) const {
+    aRetVal.SetKnownLiveString(mPrevValue);
+  }
+
+  void GetAddedAnimations(AnimationArray& aRetVal) const {
+    aRetVal = mAddedAnimations.Clone();
+  }
+
+  void GetRemovedAnimations(AnimationArray& aRetVal) const {
+    aRetVal = mRemovedAnimations.Clone();
+  }
+
+  void GetChangedAnimations(AnimationArray& aRetVal) const {
+    aRetVal = mChangedAnimations.Clone();
+  }
+
+  nsCOMPtr<nsINode> mTarget;
+  RefPtr<nsAtom> mType;
+  RefPtr<nsAtom> mAttrName;
+  nsString mAttrNamespace;
+  nsString mPrevValue;
+  RefPtr<nsSimpleContentList> mAddedNodes;
+  RefPtr<nsSimpleContentList> mRemovedNodes;
+  nsCOMPtr<nsINode> mPreviousSibling;
+  nsCOMPtr<nsINode> mNextSibling;
+  AnimationArray mAddedAnimations;
+  AnimationArray mRemovedAnimations;
+  AnimationArray mChangedAnimations;
+
+  RefPtr<nsDOMMutationRecord> mNext;
+  nsCOMPtr<nsISupports> mOwner;
+};
+
+// Base class just prevents direct access to
+// members to make sure we go through getters/setters.
+class nsMutationReceiverBase : public nsStubAnimationObserver {
+ public:
+  virtual ~nsMutationReceiverBase() = default;
+
+  nsDOMMutationObserver* Observer();
+  nsINode* Target() { return mParent ? mParent->Target() : mTarget; }
+  nsINode* RegisterTarget() { return mRegisterTarget; }
+
+  bool Subtree() { return mParent ? mParent->Subtree() : mSubtree; }
+  void SetSubtree(bool aSubtree) {
+    NS_ASSERTION(!mParent, "Shouldn't have parent");
+    mSubtree = aSubtree;
+  }
+
+  bool ChildList() { return mParent ? mParent->ChildList() : mChildList; }
+  void SetChildList(bool aChildList) {
+    NS_ASSERTION(!mParent, "Shouldn't have parent");
+    mChildList = aChildList;
+  }
+
+  bool CharacterData() {
+    return mParent ? mParent->CharacterData() : mCharacterData;
+  }
+  void SetCharacterData(bool aCharacterData) {
+    NS_ASSERTION(!mParent, "Shouldn't have parent");
+    mCharacterData = aCharacterData;
+  }
+
+  bool CharacterDataOldValue() const {
+    return mParent ? mParent->CharacterDataOldValue() : mCharacterDataOldValue;
+  }
+  void SetCharacterDataOldValue(bool aOldValue) {
+    NS_ASSERTION(!mParent, "Shouldn't have parent");
+    mCharacterDataOldValue = aOldValue;
+  }
+
+  bool Attributes() const {
+    return mParent ? mParent->Attributes() : mAttributes;
+  }
+  void SetAttributes(bool aAttributes) {
+    NS_ASSERTION(!mParent, "Shouldn't have parent");
+    mAttributes = aAttributes;
+  }
+
+  bool AllAttributes() const {
+    return mParent ? mParent->AllAttributes() : mAllAttributes;
+  }
+  void SetAllAttributes(bool aAll) {
+    NS_ASSERTION(!mParent, "Shouldn't have parent");
+    mAllAttributes = aAll;
+  }
+
+  bool Animations() const {
+    return mParent ? mParent->Animations() : mAnimations;
+  }
+  void SetAnimations(bool aAnimations) {
+    NS_ASSERTION(!mParent, "Shouldn't have parent");
+    mAnimations = aAnimations;
+  }
+
+  bool AttributeOldValue() const {
+    return mParent ? mParent->AttributeOldValue() : mAttributeOldValue;
+  }
+  void SetAttributeOldValue(bool aOldValue) {
+    NS_ASSERTION(!mParent, "Shouldn't have parent");
+    mAttributeOldValue = aOldValue;
+  }
+
+  bool ChromeOnlyNodes() const {
+    return mParent ? mParent->ChromeOnlyNodes() : mChromeOnlyNodes;
+  }
+
+  void SetChromeOnlyNodes(bool aChromeOnlyNodes) {
+    NS_ASSERTION(!mParent, "Shouldn't have parent");
+    mChromeOnlyNodes = aChromeOnlyNodes;
+  }
+
+  nsTArray<RefPtr<nsAtom>>& AttributeFilter() { return mAttributeFilter; }
+  void SetAttributeFilter(nsTArray<RefPtr<nsAtom>>&& aFilter) {
+    NS_ASSERTION(!mParent, "Shouldn't have parent");
+    mAttributeFilter.Clear();
+    mAttributeFilter = std::move(aFilter);
+  }
+
+  void AddClone(nsMutationReceiverBase* aClone) {
+    mTransientReceivers.AppendObject(aClone);
+  }
+
+  void RemoveClone(nsMutationReceiverBase* aClone) {
+    mTransientReceivers.RemoveObject(aClone);
+  }
+
+ protected:
+  nsMutationReceiverBase(nsINode* aTarget, nsDOMMutationObserver* aObserver)
+      : mTarget(aTarget),
+        mObserver(aObserver),
+        mRegisterTarget(aTarget),
+        mSubtree(false),
+        mChildList(false),
+        mCharacterData(false),
+        mCharacterDataOldValue(false),
+        mAttributes(false),
+        mAllAttributes(false),
+        mAttributeOldValue(false),
+        mAnimations(false) {}
+
+  nsMutationReceiverBase(nsINode* aRegisterTarget,
+                         nsMutationReceiverBase* aParent)
+      : mTarget(nullptr),
+        mObserver(nullptr),
+        mParent(aParent),
+        mRegisterTarget(aRegisterTarget),
+        mKungFuDeathGrip(aParent->Target()),
+        mSubtree(false),
+        mChildList(false),
+        mCharacterData(false),
+        mCharacterDataOldValue(false),
+        mAttributes(false),
+        mAllAttributes(false),
+        mAttributeOldValue(false),
+        mAnimations(false),
+        mChromeOnlyNodes(false) {
+    NS_ASSERTION(mParent->Subtree(), "Should clone a non-subtree observer!");
+  }
+
+  virtual void AddMutationObserver() = 0;
+
+  void AddObserver() {
+    AddMutationObserver();
+    mRegisterTarget->SetMayHaveDOMMutationObserver();
+    mRegisterTarget->OwnerDoc()->SetMayHaveDOMMutationObservers();
+  }
+
+  bool IsObservable(nsIContent* aContent);
+
+  bool ObservesAttr(nsINode* aRegisterTarget, mozilla::dom::Element* aElement,
+                    int32_t aNameSpaceID, nsAtom* aAttr);
+
+  // The target for the MutationObserver.observe() method.
+  nsINode* mTarget;
+  nsDOMMutationObserver* mObserver;
+  RefPtr<nsMutationReceiverBase> mParent;  // Cleared after microtask.
+  // The node to which Gecko-internal nsIMutationObserver was registered to.
+  // This is different than mTarget when dealing with transient observers.
+  nsINode* mRegisterTarget;
+  nsCOMArray<nsMutationReceiverBase> mTransientReceivers;
+  // While we have transient receivers, keep the original mutation receiver
+  // alive so it doesn't go away and disconnect all its transient receivers.
+  nsCOMPtr<nsINode> mKungFuDeathGrip;
+
+ private:
+  nsTArray<RefPtr<nsAtom>> mAttributeFilter;
+  bool mSubtree : 1;
+  bool mChildList : 1;
+  bool mCharacterData : 1;
+  bool mCharacterDataOldValue : 1;
+  bool mAttributes : 1;
+  bool mAllAttributes : 1;
+  bool mAttributeOldValue : 1;
+  bool mAnimations : 1;
+  bool mChromeOnlyNodes : 1;
+};
+
+class nsMutationReceiver : public nsMutationReceiverBase {
+ protected:
+  virtual ~nsMutationReceiver() { Disconnect(false); }
+
+ public:
+  static nsMutationReceiver* Create(nsINode* aTarget,
+                                    nsDOMMutationObserver* aObserver) {
+    nsMutationReceiver* r = new nsMutationReceiver(aTarget, aObserver);
+    r->AddObserver();
+    return r;
+  }
+
+  static nsMutationReceiver* Create(nsINode* aRegisterTarget,
+                                    nsMutationReceiverBase* aParent) {
+    nsMutationReceiver* r = new nsMutationReceiver(aRegisterTarget, aParent);
+    aParent->AddClone(r);
+    r->AddObserver();
+    return r;
+  }
+
+  nsMutationReceiver* GetParent() {
+    return static_cast<nsMutationReceiver*>(mParent.get());
+  }
+
+  void RemoveClones() {
+    for (int32_t i = 0; i < mTransientReceivers.Count(); ++i) {
+      nsMutationReceiver* r =
+          static_cast<nsMutationReceiver*>(mTransientReceivers[i]);
+      r->DisconnectTransientReceiver();
+    }
+    mTransientReceivers.Clear();
+  }
+
+  void DisconnectTransientReceiver() {
+    if (mRegisterTarget) {
+      mRegisterTarget->RemoveMutationObserver(this);
+      mRegisterTarget = nullptr;
+    }
+
+    mParent = nullptr;
+    NS_ASSERTION(!mTarget, "Should not have mTarget");
+    NS_ASSERTION(!mObserver, "Should not have mObserver");
+  }
+
+  void Disconnect(bool aRemoveFromObserver);
+
+  NS_DECL_ISUPPORTS
+
+  NS_DECL_NSIMUTATIONOBSERVER_ATTRIBUTEWILLCHANGE
+  NS_DECL_NSIMUTATIONOBSERVER_CHARACTERDATAWILLCHANGE
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTAPPENDED
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTINSERTED
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTREMOVED
+  NS_DECL_NSIMUTATIONOBSERVER_NODEWILLBEDESTROYED
+
+  virtual void AttributeSetToCurrentValue(mozilla::dom::Element* aElement,
+                                          int32_t aNameSpaceID,
+                                          nsAtom* aAttribute) override {
+    // We can reuse AttributeWillChange implementation.
+    AttributeWillChange(aElement, aNameSpaceID, aAttribute,
+                        mozilla::dom::MutationEvent_Binding::MODIFICATION);
+  }
+
+ protected:
+  nsMutationReceiver(nsINode* aTarget, nsDOMMutationObserver* aObserver);
+
+  nsMutationReceiver(nsINode* aRegisterTarget, nsMutationReceiverBase* aParent)
+      : nsMutationReceiverBase(aRegisterTarget, aParent) {
+    NS_ASSERTION(!static_cast<nsMutationReceiver*>(aParent)->GetParent(),
+                 "Shouldn't create deep observer hierarchies!");
+  }
+
+  virtual void AddMutationObserver() override {
+    mRegisterTarget->AddMutationObserver(this);
+  }
+};
+
+class nsAnimationReceiver : public nsMutationReceiver {
+ public:
+  static nsAnimationReceiver* Create(nsINode* aTarget,
+                                     nsDOMMutationObserver* aObserver) {
+    nsAnimationReceiver* r = new nsAnimationReceiver(aTarget, aObserver);
+    r->AddObserver();
+    return r;
+  }
+
+  static nsAnimationReceiver* Create(nsINode* aRegisterTarget,
+                                     nsMutationReceiverBase* aParent) {
+    nsAnimationReceiver* r = new nsAnimationReceiver(aRegisterTarget, aParent);
+    aParent->AddClone(r);
+    r->AddObserver();
+    return r;
+  }
+
+  NS_DECL_ISUPPORTS_INHERITED
+
+  NS_DECL_NSIANIMATIONOBSERVER_ANIMATIONADDED
+  NS_DECL_NSIANIMATIONOBSERVER_ANIMATIONCHANGED
+  NS_DECL_NSIANIMATIONOBSERVER_ANIMATIONREMOVED
+
+ protected:
+  virtual ~nsAnimationReceiver() = default;
+
+  nsAnimationReceiver(nsINode* aTarget, nsDOMMutationObserver* aObserver)
+      : nsMutationReceiver(aTarget, aObserver) {}
+
+  nsAnimationReceiver(nsINode* aRegisterTarget, nsMutationReceiverBase* aParent)
+      : nsMutationReceiver(aRegisterTarget, aParent) {}
+
+  virtual void AddMutationObserver() override {
+    mRegisterTarget->AddAnimationObserver(this);
+  }
+
+ private:
+  enum AnimationMutation {
+    eAnimationMutation_Added,
+    eAnimationMutation_Changed,
+    eAnimationMutation_Removed
+  };
+
+  void RecordAnimationMutation(mozilla::dom::Animation* aAnimation,
+                               AnimationMutation aMutationType);
+};
+
+#define NS_DOM_MUTATION_OBSERVER_IID                 \
+  {                                                  \
+    0x0c3b91f8, 0xcc3b, 0x4b08, {                    \
+      0x9e, 0xab, 0x07, 0x47, 0xa9, 0xe4, 0x65, 0xb4 \
+    }                                                \
+  }
+
+class nsDOMMutationObserver final : public nsISupports, public nsWrapperCache {
+ public:
+  nsDOMMutationObserver(nsCOMPtr<nsPIDOMWindowInner>&& aOwner,
+                        mozilla::dom::MutationCallback& aCb)
+      : mOwner(std::move(aOwner)),
+        mLastPendingMutation(nullptr),
+        mPendingMutationCount(0),
+        mCallback(&aCb),
+        mWaitingForRun(false),
+        mMergeAttributeRecords(false),
+        mId(++sCount) {}
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(nsDOMMutationObserver)
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_DOM_MUTATION_OBSERVER_IID)
+
+  static already_AddRefed<nsDOMMutationObserver> Constructor(
+      const mozilla::dom::GlobalObject&, mozilla::dom::MutationCallback&,
+      mozilla::ErrorResult&);
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override {
+    return mozilla::dom::MutationObserver_Binding::Wrap(aCx, this, aGivenProto);
+  }
+
+  nsISupports* GetParentObject() const { return mOwner; }
+
+  void Observe(nsINode& aTarget,
+               const mozilla::dom::MutationObserverInit& aOptions,
+               nsIPrincipal& aSubjectPrincipal, mozilla::ErrorResult& aRv);
+
+  void Disconnect();
+
+  void TakeRecords(nsTArray<RefPtr<nsDOMMutationRecord>>& aRetVal);
+
+  MOZ_CAN_RUN_SCRIPT void HandleMutation();
+
+  void GetObservingInfo(
+      nsTArray<mozilla::dom::Nullable<MutationObservingInfo>>& aResult,
+      mozilla::ErrorResult& aRv);
+
+  mozilla::dom::MutationCallback* MutationCallback() { return mCallback; }
+
+  bool MergeAttributeRecords() { return mMergeAttributeRecords; }
+
+  void SetMergeAttributeRecords(bool aVal) { mMergeAttributeRecords = aVal; }
+
+  // If both records are for 'attributes' type and for the same target and
+  // attribute name and namespace are the same, we can skip the newer record.
+  // aOldRecord->mPrevValue holds the original value, if observed.
+  bool MergeableAttributeRecord(nsDOMMutationRecord* aOldRecord,
+                                nsDOMMutationRecord* aRecord);
+
+  void AppendMutationRecord(already_AddRefed<nsDOMMutationRecord> aRecord) {
+    RefPtr<nsDOMMutationRecord> record = aRecord;
+    MOZ_ASSERT(record);
+    if (!mLastPendingMutation) {
+      MOZ_ASSERT(!mFirstPendingMutation);
+      mFirstPendingMutation = std::move(record);
+      mLastPendingMutation = mFirstPendingMutation;
+    } else {
+      MOZ_ASSERT(mFirstPendingMutation);
+      mLastPendingMutation->mNext = std::move(record);
+      mLastPendingMutation = mLastPendingMutation->mNext;
+    }
+    ++mPendingMutationCount;
+  }
+
+  void ClearPendingRecords() {
+    // Break down the pending mutation record list so that cycle collector
+    // can delete the objects sooner.
+    RefPtr<nsDOMMutationRecord> current = std::move(mFirstPendingMutation);
+    mLastPendingMutation = nullptr;
+    mPendingMutationCount = 0;
+    while (current) {
+      current = std::move(current->mNext);
+    }
+  }
+
+  // static methods
+  static void QueueMutationObserverMicroTask();
+
+  MOZ_CAN_RUN_SCRIPT
+  static void HandleMutations(mozilla::AutoSlowOperation& aAso);
+
+  static bool AllScheduledMutationObserversAreSuppressed() {
+    if (sScheduledMutationObservers) {
+      uint32_t len = sScheduledMutationObservers->Length();
+      if (len > 0) {
+        for (uint32_t i = 0; i < len; ++i) {
+          if (!(*sScheduledMutationObservers)[i]->Suppressed()) {
+            return false;
+          }
+        }
+        return true;
+      }
+    }
+    return false;
+  }
+
+  static void EnterMutationHandling();
+  static void LeaveMutationHandling();
+
+  static void Shutdown();
+
+ protected:
+  virtual ~nsDOMMutationObserver();
+
+  friend class nsMutationReceiver;
+  friend class nsAnimationReceiver;
+  friend class nsAutoMutationBatch;
+  friend class nsAutoAnimationMutationBatch;
+  nsMutationReceiver* GetReceiverFor(nsINode* aNode, bool aMayCreate,
+                                     bool aWantsAnimations);
+  void RemoveReceiver(nsMutationReceiver* aReceiver);
+
+  void GetAllSubtreeObserversFor(nsINode* aNode,
+                                 nsTArray<nsMutationReceiver*>& aObservers);
+  void ScheduleForRun();
+  void RescheduleForRun();
+
+  nsDOMMutationRecord* CurrentRecord(nsAtom* aType);
+  bool HasCurrentRecord(const nsAString& aType);
+
+  bool Suppressed() {
+    return mOwner && nsGlobalWindowInner::Cast(mOwner)->IsInSyncOperation();
+  }
+
+  MOZ_CAN_RUN_SCRIPT
+  static void HandleMutationsInternal(mozilla::AutoSlowOperation& aAso);
+
+  static void AddCurrentlyHandlingObserver(nsDOMMutationObserver* aObserver,
+                                           uint32_t aMutationLevel);
+
+  nsCOMPtr<nsPIDOMWindowInner> mOwner;
+
+  nsCOMArray<nsMutationReceiver> mReceivers;
+  nsClassHashtable<nsISupportsHashKey, nsCOMArray<nsMutationReceiver>>
+      mTransientReceivers;
+  // MutationRecords which are being constructed.
+  AutoTArray<nsDOMMutationRecord*, 4> mCurrentMutations;
+  // MutationRecords which will be handed to the callback at the end of
+  // the microtask.
+  RefPtr<nsDOMMutationRecord> mFirstPendingMutation;
+  nsDOMMutationRecord* mLastPendingMutation;
+  uint32_t mPendingMutationCount;
+
+  RefPtr<mozilla::dom::MutationCallback> mCallback;
+
+  bool mWaitingForRun;
+  bool mMergeAttributeRecords;
+
+  uint64_t mId;
+
+  static uint64_t sCount;
+  static AutoTArray<RefPtr<nsDOMMutationObserver>, 4>*
+      sScheduledMutationObservers;
+
+  static uint32_t sMutationLevel;
+  static AutoTArray<AutoTArray<RefPtr<nsDOMMutationObserver>, 4>, 4>*
+      sCurrentlyHandlingObservers;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsDOMMutationObserver,
+                              NS_DOM_MUTATION_OBSERVER_IID)
+
+class nsAutoMutationBatch {
+ public:
+  nsAutoMutationBatch()
+      : mPreviousBatch(nullptr),
+        mBatchTarget(nullptr),
+        mRemovalDone(false),
+        mFromFirstToLast(false),
+        mAllowNestedBatches(false) {}
+
+  nsAutoMutationBatch(nsINode* aTarget, bool aFromFirstToLast,
+                      bool aAllowNestedBatches)
+      : mPreviousBatch(nullptr),
+        mBatchTarget(nullptr),
+        mRemovalDone(false),
+        mFromFirstToLast(false),
+        mAllowNestedBatches(false) {
+    Init(aTarget, aFromFirstToLast, aAllowNestedBatches);
+  }
+
+  void Init(nsINode* aTarget, bool aFromFirstToLast, bool aAllowNestedBatches) {
+    if (aTarget && aTarget->OwnerDoc()->MayHaveDOMMutationObservers()) {
+      if (sCurrentBatch && !sCurrentBatch->mAllowNestedBatches) {
+        return;
+      }
+      mBatchTarget = aTarget;
+      mFromFirstToLast = aFromFirstToLast;
+      mAllowNestedBatches = aAllowNestedBatches;
+      mPreviousBatch = sCurrentBatch;
+      sCurrentBatch = this;
+      nsDOMMutationObserver::EnterMutationHandling();
+    }
+  }
+
+  void RemovalDone() { mRemovalDone = true; }
+  static bool IsRemovalDone() { return sCurrentBatch->mRemovalDone; }
+
+  void SetPrevSibling(nsINode* aNode) { mPrevSibling = aNode; }
+  void SetNextSibling(nsINode* aNode) { mNextSibling = aNode; }
+
+  void Done();
+
+  ~nsAutoMutationBatch() { NodesAdded(); }
+
+  static bool IsBatching() { return !!sCurrentBatch; }
+
+  static nsAutoMutationBatch* GetCurrentBatch() { return sCurrentBatch; }
+
+  static void UpdateObserver(nsDOMMutationObserver* aObserver,
+                             bool aWantsChildList) {
+    uint32_t l = sCurrentBatch->mObservers.Length();
+    for (uint32_t i = 0; i < l; ++i) {
+      if (sCurrentBatch->mObservers[i].mObserver == aObserver) {
+        if (aWantsChildList) {
+          sCurrentBatch->mObservers[i].mWantsChildList = aWantsChildList;
+        }
+        return;
+      }
+    }
+    BatchObserver* bo = sCurrentBatch->mObservers.AppendElement();
+    bo->mObserver = aObserver;
+    bo->mWantsChildList = aWantsChildList;
+  }
+
+  static nsINode* GetBatchTarget() { return sCurrentBatch->mBatchTarget; }
+
+  // Mutation receivers notify the batch about removed child nodes.
+  static void NodeRemoved(nsIContent* aChild) {
+    if (IsBatching() && !sCurrentBatch->mRemovalDone) {
+      uint32_t len = sCurrentBatch->mRemovedNodes.Length();
+      if (!len || sCurrentBatch->mRemovedNodes[len - 1] != aChild) {
+        sCurrentBatch->mRemovedNodes.AppendElement(aChild);
+      }
+    }
+  }
+
+  // Called after new child nodes have been added to the batch target.
+  void NodesAdded() {
+    if (sCurrentBatch != this) {
+      return;
+    }
+
+    nsIContent* c = mPrevSibling ? mPrevSibling->GetNextSibling()
+                                 : mBatchTarget->GetFirstChild();
+    for (; c != mNextSibling; c = c->GetNextSibling()) {
+      mAddedNodes.AppendElement(c);
+    }
+    Done();
+  }
+
+ private:
+  struct BatchObserver {
+    nsDOMMutationObserver* mObserver;
+    bool mWantsChildList;
+  };
+
+  static nsAutoMutationBatch* sCurrentBatch;
+  nsAutoMutationBatch* mPreviousBatch;
+  AutoTArray<BatchObserver, 2> mObservers;
+  nsTArray<nsCOMPtr<nsIContent>> mRemovedNodes;
+  nsTArray<nsCOMPtr<nsIContent>> mAddedNodes;
+  nsINode* mBatchTarget;
+  bool mRemovalDone;
+  bool mFromFirstToLast;
+  bool mAllowNestedBatches;
+  nsCOMPtr<nsINode> mPrevSibling;
+  nsCOMPtr<nsINode> mNextSibling;
+};
+
+class nsAutoAnimationMutationBatch {
+  struct Entry;
+
+ public:
+  explicit nsAutoAnimationMutationBatch(mozilla::dom::Document* aDocument) {
+    Init(aDocument);
+  }
+
+  void Init(mozilla::dom::Document* aDocument) {
+    if (!aDocument || !aDocument->MayHaveDOMMutationObservers() ||
+        sCurrentBatch) {
+      return;
+    }
+
+    sCurrentBatch = this;
+    nsDOMMutationObserver::EnterMutationHandling();
+  }
+
+  ~nsAutoAnimationMutationBatch() { Done(); }
+
+  void Done();
+
+  static bool IsBatching() { return !!sCurrentBatch; }
+
+  static nsAutoAnimationMutationBatch* GetCurrentBatch() {
+    return sCurrentBatch;
+  }
+
+  static void AddObserver(nsDOMMutationObserver* aObserver) {
+    if (sCurrentBatch->mObservers.Contains(aObserver)) {
+      return;
+    }
+    sCurrentBatch->mObservers.AppendElement(aObserver);
+  }
+
+  static void AnimationAdded(mozilla::dom::Animation* aAnimation,
+                             nsINode* aTarget) {
+    if (!IsBatching()) {
+      return;
+    }
+
+    Entry* entry = sCurrentBatch->FindEntry(aAnimation, aTarget);
+    if (entry) {
+      switch (entry->mState) {
+        case eState_RemainedAbsent:
+          entry->mState = eState_Added;
+          break;
+        case eState_Removed:
+          entry->mState = eState_RemainedPresent;
+          break;
+        case eState_Added:
+          // FIXME bug 1189015
+          NS_ERROR("shouldn't have observed an animation being added twice");
+          break;
+        case eState_RemainedPresent:
+          MOZ_ASSERT_UNREACHABLE(
+              "shouldn't have observed an animation "
+              "remaining present");
+          break;
+      }
+    } else {
+      entry = sCurrentBatch->AddEntry(aAnimation, aTarget);
+      entry->mState = eState_Added;
+      entry->mChanged = false;
+    }
+  }
+
+  static void AnimationChanged(mozilla::dom::Animation* aAnimation,
+                               nsINode* aTarget) {
+    Entry* entry = sCurrentBatch->FindEntry(aAnimation, aTarget);
+    if (entry) {
+      NS_ASSERTION(entry->mState == eState_RemainedPresent ||
+                       entry->mState == eState_Added,
+                   "shouldn't have observed an animation being changed after "
+                   "being removed");
+      entry->mChanged = true;
+    } else {
+      entry = sCurrentBatch->AddEntry(aAnimation, aTarget);
+      entry->mState = eState_RemainedPresent;
+      entry->mChanged = true;
+    }
+  }
+
+  static void AnimationRemoved(mozilla::dom::Animation* aAnimation,
+                               nsINode* aTarget) {
+    Entry* entry = sCurrentBatch->FindEntry(aAnimation, aTarget);
+    if (entry) {
+      switch (entry->mState) {
+        case eState_RemainedPresent:
+          entry->mState = eState_Removed;
+          break;
+        case eState_Added:
+          entry->mState = eState_RemainedAbsent;
+          break;
+        case eState_RemainedAbsent:
+          MOZ_ASSERT_UNREACHABLE(
+              "shouldn't have observed an animation "
+              "remaining absent");
+          break;
+        case eState_Removed:
+          // FIXME bug 1189015
+          NS_ERROR("shouldn't have observed an animation being removed twice");
+          break;
+      }
+    } else {
+      entry = sCurrentBatch->AddEntry(aAnimation, aTarget);
+      entry->mState = eState_Removed;
+      entry->mChanged = false;
+    }
+  }
+
+ private:
+  Entry* FindEntry(mozilla::dom::Animation* aAnimation, nsINode* aTarget) {
+    EntryArray* entries = mEntryTable.Get(aTarget);
+    if (!entries) {
+      return nullptr;
+    }
+
+    for (Entry& e : *entries) {
+      if (e.mAnimation == aAnimation) {
+        return &e;
+      }
+    }
+    return nullptr;
+  }
+
+  Entry* AddEntry(mozilla::dom::Animation* aAnimation, nsINode* aTarget) {
+    EntryArray* entries = sCurrentBatch->mEntryTable.GetOrInsertNew(aTarget);
+    if (entries->IsEmpty()) {
+      sCurrentBatch->mBatchTargets.AppendElement(aTarget);
+    }
+    Entry* entry = entries->AppendElement();
+    entry->mAnimation = aAnimation;
+    return entry;
+  }
+
+  enum State {
+    eState_RemainedPresent,
+    eState_RemainedAbsent,
+    eState_Added,
+    eState_Removed
+  };
+
+  struct Entry {
+    RefPtr<mozilla::dom::Animation> mAnimation;
+    State mState;
+    bool mChanged;
+  };
+
+  static nsAutoAnimationMutationBatch* sCurrentBatch;
+  AutoTArray<nsDOMMutationObserver*, 2> mObservers;
+  using EntryArray = nsTArray<Entry>;
+  nsClassHashtable<nsPtrHashKey<nsINode>, EntryArray> mEntryTable;
+  // List of nodes referred to by mEntryTable so we can sort them
+  // For a specific pseudo element, we use its parent element as the
+  // batch target, so they will be put in the same EntryArray.
+  nsTArray<nsINode*> mBatchTargets;
+};
+
+inline nsDOMMutationObserver* nsMutationReceiverBase::Observer() {
+  return mParent ? mParent->Observer()
+                 : static_cast<nsDOMMutationObserver*>(mObserver);
+}
+
+class MOZ_RAII nsDOMMutationEnterLeave {
+ public:
+  explicit nsDOMMutationEnterLeave(mozilla::dom::Document* aDoc)
+      : mNeeded(aDoc->MayHaveDOMMutationObservers()) {
+    if (mNeeded) {
+      nsDOMMutationObserver::EnterMutationHandling();
+    }
+  }
+  ~nsDOMMutationEnterLeave() {
+    if (mNeeded) {
+      nsDOMMutationObserver::LeaveMutationHandling();
+    }
+  }
+
+ private:
+  const bool mNeeded;
+};
+
+#endif