1 files changed, 655 insertions, 0 deletions
diff --git a/dom/base/nsContentList.h b/dom/base/nsContentList.h
new file mode 100644
index 0000000000..a70c5281b2
--- /dev/null
+++ b/dom/base/nsContentList.h
@@ -0,0 +1,655 @@
+/* -*- 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/. */
+
+/*
+ * nsBaseContentList is a basic list of content nodes; nsContentList
+ * is a commonly used NodeList implementation (used for
+ * getElementsByTagName, some properties on HTMLDocument/Document, etc).
+ */
+
+#ifndef nsContentList_h___
+#define nsContentList_h___
+
+#include "mozilla/Attributes.h"
+#include "nsContentListDeclarations.h"
+#include "nsISupports.h"
+#include "nsTArray.h"
+#include "nsString.h"
+#include "nsIHTMLCollection.h"
+#include "nsINodeList.h"
+#include "nsStubMutationObserver.h"
+#include "nsAtomHashKeys.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsNameSpaceManager.h"
+#include "nsWrapperCache.h"
+#include "nsHashKeys.h"
+#include "mozilla/HashFunctions.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/dom/NameSpaceConstants.h"
+
+// XXX Avoid including this here by moving function bodies to the cpp file.
+#include "nsIContent.h"
+
+namespace mozilla::dom {
+class Element;
+}  // namespace mozilla::dom
+
+class nsBaseContentList : public nsINodeList {
+ protected:
+  using Element = mozilla::dom::Element;
+
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+
+  // nsINodeList
+  int32_t IndexOf(nsIContent* aContent) override;
+  nsIContent* Item(uint32_t aIndex) override;
+
+  uint32_t Length() override { return mElements.Length(); }
+
+  NS_DECL_CYCLE_COLLECTION_SKIPPABLE_WRAPPERCACHE_CLASS(nsBaseContentList)
+
+  void AppendElement(nsIContent* aContent) {
+    MOZ_ASSERT(aContent);
+    mElements.AppendElement(aContent);
+  }
+  void MaybeAppendElement(nsIContent* aContent) {
+    if (aContent) {
+      AppendElement(aContent);
+    }
+  }
+
+  /**
+   * Insert the element at a given index, shifting the objects at
+   * the given index and later to make space.
+   * @param aContent Element to insert, must not be null
+   * @param aIndex Index to insert the element at.
+   */
+  void InsertElementAt(nsIContent* aContent, int32_t aIndex) {
+    NS_ASSERTION(aContent, "Element to insert must not be null");
+    mElements.InsertElementAt(aIndex, aContent);
+  }
+
+  void RemoveElement(nsIContent* aContent) {
+    mElements.RemoveElement(aContent);
+  }
+
+  void Reset() { mElements.Clear(); }
+
+  virtual int32_t IndexOf(nsIContent* aContent, bool aDoFlush);
+
+  JSObject* WrapObject(JSContext* cx,
+                       JS::Handle<JSObject*> aGivenProto) override = 0;
+
+  void SetCapacity(uint32_t aCapacity) { mElements.SetCapacity(aCapacity); }
+
+  virtual void LastRelease() {}
+
+  // Memory reporting.  For now, subclasses of nsBaseContentList don't really
+  // need to report any members that are not part of the object itself, so we
+  // don't need to make this virtual.
+  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+
+ protected:
+  virtual ~nsBaseContentList();
+
+  /**
+   * To be called from non-destructor locations (e.g. unlink) that want to
+   * remove from caches.  Cacheable subclasses should override.
+   */
+  virtual void RemoveFromCaches() {}
+
+  AutoTArray<nsCOMPtr<nsIContent>, 10> mElements;
+};
+
+class nsSimpleContentList : public nsBaseContentList {
+ public:
+  explicit nsSimpleContentList(nsINode* aRoot)
+      : nsBaseContentList(), mRoot(aRoot) {}
+
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(nsSimpleContentList,
+                                           nsBaseContentList)
+
+  nsINode* GetParentObject() override { return mRoot; }
+  JSObject* WrapObject(JSContext* cx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+ protected:
+  virtual ~nsSimpleContentList() = default;
+
+ private:
+  // This has to be a strong reference, the root might go away before the list.
+  nsCOMPtr<nsINode> mRoot;
+};
+
+// Used for returning lists that will always be empty, such as the applets list
+// in HTML Documents
+class nsEmptyContentList final : public nsBaseContentList,
+                                 public nsIHTMLCollection {
+ public:
+  explicit nsEmptyContentList(nsINode* aRoot)
+      : nsBaseContentList(), mRoot(aRoot) {}
+
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(nsEmptyContentList,
+                                           nsBaseContentList)
+
+  nsINode* GetParentObject() override { return mRoot; }
+
+  JSObject* WrapObject(JSContext* cx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  JSObject* GetWrapperPreserveColorInternal() override {
+    return nsWrapperCache::GetWrapperPreserveColor();
+  }
+  void PreserveWrapperInternal(nsISupports* aScriptObjectHolder) override {
+    nsWrapperCache::PreserveWrapper(aScriptObjectHolder);
+  }
+
+  uint32_t Length() final { return 0; }
+  nsIContent* Item(uint32_t aIndex) override;
+  Element* GetElementAt(uint32_t index) override;
+  Element* GetFirstNamedElement(const nsAString& aName, bool& aFound) override;
+  void GetSupportedNames(nsTArray<nsString>& aNames) override;
+
+ protected:
+  virtual ~nsEmptyContentList() = default;
+
+ private:
+  // This has to be a strong reference, the root might go away before the list.
+  nsCOMPtr<nsINode> mRoot;
+};
+
+/**
+ * Class that's used as the key to hash nsContentList implementations
+ * for fast retrieval
+ */
+struct nsContentListKey {
+  // We have to take an aIsHTMLDocument arg for two reasons:
+  // 1) We don't want to include Document.h in this header.
+  // 2) We need to do that to make nsContentList::RemoveFromHashtable
+  //    work, because by the time it's called the document of the
+  //    list's root node might have changed.
+  nsContentListKey(nsINode* aRootNode, int32_t aMatchNameSpaceId,
+                   const nsAString& aTagname, bool aIsHTMLDocument)
+      : mRootNode(aRootNode),
+        mMatchNameSpaceId(aMatchNameSpaceId),
+        mTagname(aTagname),
+        mIsHTMLDocument(aIsHTMLDocument),
+        mHash(mozilla::AddToHash(mozilla::HashString(aTagname), mRootNode,
+                                 mMatchNameSpaceId, mIsHTMLDocument)) {}
+
+  nsContentListKey(const nsContentListKey& aContentListKey) = default;
+
+  inline uint32_t GetHash(void) const { return mHash; }
+
+  nsINode* const mRootNode;  // Weak ref
+  const int32_t mMatchNameSpaceId;
+  const nsAString& mTagname;
+  bool mIsHTMLDocument;
+  const uint32_t mHash;
+};
+
+/**
+ * Class that implements a possibly live NodeList that matches Elements
+ * in the tree based on some criterion.
+ */
+class nsContentList : public nsBaseContentList,
+                      public nsIHTMLCollection,
+                      public nsStubMutationObserver {
+ protected:
+  enum class State : uint8_t {
+    // The list is up to date and need not do any walking to be able to answer
+    // any questions anyone may have.
+    UpToDate = 0,
+    // The list contains no useful information and if anyone asks it anything it
+    // will have to populate itself before answering.
+    Dirty,
+    // The list has populated itself to a certain extent and that that part of
+    // the list is still valid.  Requests for things outside that part of the
+    // list will require walking the tree some more.  When a list is in this
+    // state, the last thing in mElements is the last node in the tree that the
+    // list looked at.
+    Lazy,
+  };
+
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+
+  /**
+   * @param aRootNode The node under which to limit our search.
+   * @param aMatchAtom An atom whose meaning depends on aMatchNameSpaceId.
+   *                   The special value "*" always matches whatever aMatchAtom
+   *                   is matched against.
+   * @param aMatchNameSpaceId If kNameSpaceID_Unknown, then aMatchAtom is the
+   *                          tagName to match.
+   *                          If kNameSpaceID_Wildcard, then aMatchAtom is the
+   *                          localName to match.
+   *                          Otherwise we match nodes whose namespace is
+   *                          aMatchNameSpaceId and localName matches
+   *                          aMatchAtom.
+   * @param aDeep If false, then look only at children of the root, nothing
+   *              deeper.  If true, then look at the whole subtree rooted at
+   *              our root.
+   * @param aLiveList Whether the created list should be a live list observing
+   *                  mutations to the DOM tree.
+   */
+  nsContentList(nsINode* aRootNode, int32_t aMatchNameSpaceId,
+                nsAtom* aHTMLMatchAtom, nsAtom* aXMLMatchAtom,
+                bool aDeep = true, bool aLiveList = true);
+
+  /**
+   * @param aRootNode The node under which to limit our search.
+   * @param aFunc the function to be called to determine whether we match.
+   *              This function MUST NOT ever cause mutation of the DOM.
+   *              The nsContentList implementation guarantees that everything
+   *              passed to the function will be IsElement().
+   * @param aDestroyFunc the function that will be called to destroy aData
+   * @param aData closure data that will need to be passed back to aFunc
+   * @param aDeep If false, then look only at children of the root, nothing
+   *              deeper.  If true, then look at the whole subtree rooted at
+   *              our root.
+   * @param aMatchAtom an atom to be passed back to aFunc
+   * @param aMatchNameSpaceId a namespace id to be passed back to aFunc
+   * @param aFuncMayDependOnAttr a boolean that indicates whether this list is
+   *                             sensitive to attribute changes.
+   * @param aLiveList Whether the created list should be a live list observing
+   *                  mutations to the DOM tree.
+   */
+  nsContentList(nsINode* aRootNode, nsContentListMatchFunc aFunc,
+                nsContentListDestroyFunc aDestroyFunc, void* aData,
+                bool aDeep = true, nsAtom* aMatchAtom = nullptr,
+                int32_t aMatchNameSpaceId = kNameSpaceID_None,
+                bool aFuncMayDependOnAttr = true, bool aLiveList = true);
+
+  // nsWrapperCache
+  using nsWrapperCache::GetWrapperPreserveColor;
+  using nsWrapperCache::PreserveWrapper;
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+ protected:
+  virtual ~nsContentList();
+
+  JSObject* GetWrapperPreserveColorInternal() override {
+    return nsWrapperCache::GetWrapperPreserveColor();
+  }
+  void PreserveWrapperInternal(nsISupports* aScriptObjectHolder) override {
+    nsWrapperCache::PreserveWrapper(aScriptObjectHolder);
+  }
+
+ public:
+  // nsBaseContentList overrides
+  int32_t IndexOf(nsIContent* aContent, bool aDoFlush) override;
+  int32_t IndexOf(nsIContent* aContent) override;
+  nsINode* GetParentObject() override { return mRootNode; }
+
+  uint32_t Length() final { return Length(true); }
+  nsIContent* Item(uint32_t aIndex) final;
+  Element* GetElementAt(uint32_t index) override;
+  Element* GetFirstNamedElement(const nsAString& aName, bool& aFound) override {
+    Element* item = NamedItem(aName, true);
+    aFound = !!item;
+    return item;
+  }
+  void GetSupportedNames(nsTArray<nsString>& aNames) override;
+
+  // nsContentList public methods
+  uint32_t Length(bool aDoFlush);
+  nsIContent* Item(uint32_t aIndex, bool aDoFlush);
+  Element* NamedItem(const nsAString& aName, bool aDoFlush);
+
+  // nsIMutationObserver
+  NS_DECL_NSIMUTATIONOBSERVER_ATTRIBUTECHANGED
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTAPPENDED
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTINSERTED
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTREMOVED
+  NS_DECL_NSIMUTATIONOBSERVER_NODEWILLBEDESTROYED
+
+  static nsContentList* FromSupports(nsISupports* aSupports) {
+    nsINodeList* list = static_cast<nsINodeList*>(aSupports);
+#ifdef DEBUG
+    {
+      nsCOMPtr<nsINodeList> list_qi = do_QueryInterface(aSupports);
+
+      // If this assertion fires the QI implementation for the object in
+      // question doesn't use the nsINodeList pointer as the nsISupports
+      // pointer. That must be fixed, or we'll crash...
+      NS_ASSERTION(list_qi == list, "Uh, fix QI!");
+    }
+#endif
+    return static_cast<nsContentList*>(list);
+  }
+
+  bool MatchesKey(const nsContentListKey& aKey) const {
+    // The root node is most commonly the same: the document.  And the
+    // most common namespace id is kNameSpaceID_Unknown.  So check the
+    // string first.  Cases in which whether our root's ownerDocument
+    // is HTML changes are extremely rare, so check those last.
+    MOZ_ASSERT(mXMLMatchAtom,
+               "How did we get here with a null match atom on our list?");
+    return mXMLMatchAtom->Equals(aKey.mTagname) &&
+           mRootNode == aKey.mRootNode &&
+           mMatchNameSpaceId == aKey.mMatchNameSpaceId &&
+           mIsHTMLDocument == aKey.mIsHTMLDocument;
+  }
+
+  /**
+   * Sets the state to LIST_DIRTY and clears mElements array.
+   * @note This is the only acceptable way to set state to LIST_DIRTY.
+   */
+  void SetDirty() {
+    mState = State::Dirty;
+    InvalidateNamedItemsCache();
+    Reset();
+    SetEnabledCallbacks(nsIMutationObserver::kNodeWillBeDestroyed);
+  }
+
+  void LastRelease() override;
+
+  class HashEntry;
+
+ protected:
+  // A cache from name to the first named item in mElements. Only possibly
+  // non-null when mState is State::UpToDate. Elements are kept alive by our
+  // mElements array.
+  using NamedItemsCache = nsTHashMap<nsAtomHashKey, Element*>;
+
+  void InvalidateNamedItemsCache() {
+    mNamedItemsCache = nullptr;
+    mNamedItemsCacheValid = false;
+  }
+
+  inline void InsertElementInNamedItemsCache(nsIContent&);
+  inline void InvalidateNamedItemsCacheForAttributeChange(int32_t aNameSpaceID,
+                                                          nsAtom* aAttribute);
+  inline void InvalidateNamedItemsCacheForInsertion(Element&);
+  inline void InvalidateNamedItemsCacheForDeletion(Element&);
+
+  void EnsureNamedItemsCacheValid(bool aDoFlush);
+
+  /**
+   * Returns whether the element matches our criterion
+   *
+   * @param  aElement the element to attempt to match
+   * @return whether we match
+   */
+  bool Match(Element* aElement);
+  /**
+   * See if anything in the subtree rooted at aContent, including
+   * aContent itself, matches our criterion.
+   *
+   * @param  aContent the root of the subtree to match against
+   * @return whether we match something in the tree rooted at aContent
+   */
+  bool MatchSelf(nsIContent* aContent);
+
+  /**
+   * Populate our list.  Stop once we have at least aNeededLength
+   * elements.  At the end of PopulateSelf running, either the last
+   * node we examined is the last node in our array or we have
+   * traversed the whole document (or both).
+   *
+   * @param aNeededLength the length the list should have when we are
+   *        done (unless it exhausts the document)
+   * @param aExpectedElementsIfDirty is for debugging only to
+   *        assert that mElements has expected number of entries.
+   */
+  virtual void PopulateSelf(uint32_t aNeededLength,
+                            uint32_t aExpectedElementsIfDirty = 0);
+
+  /**
+   * @param  aContainer a content node which must be a descendant of
+   *         mRootNode
+   * @return true if children or descendants of aContainer could match our
+   *                 criterion.
+   *         false otherwise.
+   */
+  bool MayContainRelevantNodes(nsINode* aContainer) {
+    return mDeep || aContainer == mRootNode;
+  }
+
+  /**
+   * Remove ourselves from the hashtable that caches commonly accessed
+   * content lists.  Generally done on destruction.
+   */
+  void RemoveFromHashtable();
+  /**
+   * If state is not LIST_UP_TO_DATE, fully populate ourselves with
+   * all the nodes we can find.
+   */
+  inline void BringSelfUpToDate(bool aDoFlush);
+
+  /**
+   * To be called from non-destructor locations that want to remove from caches.
+   * Needed because if subclasses want to have cache behavior they can't just
+   * override RemoveFromHashtable(), since we call that in our destructor.
+   */
+  void RemoveFromCaches() override { RemoveFromHashtable(); }
+
+  void MaybeMarkDirty() {
+    if (mState != State::Dirty && ++mMissedUpdates > 128) {
+      mMissedUpdates = 0;
+      SetDirty();
+    }
+  }
+
+  nsINode* mRootNode;  // Weak ref
+  int32_t mMatchNameSpaceId;
+  RefPtr<nsAtom> mHTMLMatchAtom;
+  RefPtr<nsAtom> mXMLMatchAtom;
+
+  /**
+   * Function to use to determine whether a piece of content matches
+   * our criterion
+   */
+  nsContentListMatchFunc mFunc = nullptr;
+  /**
+   * Cleanup closure data with this.
+   */
+  nsContentListDestroyFunc mDestroyFunc = nullptr;
+  /**
+   * Closure data to pass to mFunc when we call it
+   */
+  void* mData = nullptr;
+
+  mozilla::UniquePtr<NamedItemsCache> mNamedItemsCache;
+
+  uint8_t mMissedUpdates = 0;
+
+  // The current state of the list.
+  State mState;
+
+  /**
+   * True if we are looking for elements named "*"
+   */
+  bool mMatchAll : 1;
+  /**
+   * Whether to actually descend the tree.  If this is false, we won't
+   * consider grandkids of mRootNode.
+   */
+  bool mDeep : 1;
+  /**
+   * Whether the return value of mFunc could depend on the values of
+   * attributes.
+   */
+  bool mFuncMayDependOnAttr : 1;
+  /**
+   * Whether we actually need to flush to get our state correct.
+   */
+  bool mFlushesNeeded : 1;
+  /**
+   * Whether the ownerDocument of our root node at list creation time was an
+   * HTML document.  Only needed when we're doing a namespace/atom match, not
+   * when doing function matching, always false otherwise.
+   */
+  bool mIsHTMLDocument : 1;
+  /**
+   * True mNamedItemsCache is valid. Note mNamedItemsCache might still be null
+   * if there's no named items at all.
+   */
+  bool mNamedItemsCacheValid : 1;
+  /**
+   * Whether the list observes mutations to the DOM tree.
+   */
+  const bool mIsLiveList : 1;
+  /*
+   * True if this content list is cached in a hash table.
+   * For nsContentList (but not its subclasses), the hash table is
+   * gContentListHashTable.
+   * For nsCacheableFuncStringContentList, the hash table is
+   * gFuncStringContentListHashTable.
+   * Other subclasses of nsContentList can't be in hash tables.
+   */
+  bool mInHashtable : 1;
+
+#ifdef DEBUG_CONTENT_LIST
+  void AssertInSync();
+#endif
+};
+
+/**
+ * A class of cacheable content list; cached on the combination of aRootNode +
+ * aFunc + aDataString
+ */
+class nsCacheableFuncStringContentList;
+
+class MOZ_STACK_CLASS nsFuncStringCacheKey {
+ public:
+  nsFuncStringCacheKey(nsINode* aRootNode, nsContentListMatchFunc aFunc,
+                       const nsAString& aString)
+      : mRootNode(aRootNode), mFunc(aFunc), mString(aString) {}
+
+  uint32_t GetHash(void) const {
+    uint32_t hash = mozilla::HashString(mString);
+    return mozilla::AddToHash(hash, mRootNode, mFunc);
+  }
+
+ private:
+  friend class nsCacheableFuncStringContentList;
+
+  nsINode* const mRootNode;
+  const nsContentListMatchFunc mFunc;
+  const nsAString& mString;
+};
+
+// aDestroyFunc is allowed to be null
+// aDataAllocator must always return a non-null pointer
+class nsCacheableFuncStringContentList : public nsContentList {
+ public:
+  virtual ~nsCacheableFuncStringContentList();
+
+  bool Equals(const nsFuncStringCacheKey* aKey) {
+    return mRootNode == aKey->mRootNode && mFunc == aKey->mFunc &&
+           mString == aKey->mString;
+  }
+
+  enum ContentListType { eNodeList, eHTMLCollection };
+#ifdef DEBUG
+  ContentListType mType;
+#endif
+
+  class HashEntry;
+
+ protected:
+  nsCacheableFuncStringContentList(
+      nsINode* aRootNode, nsContentListMatchFunc aFunc,
+      nsContentListDestroyFunc aDestroyFunc,
+      nsFuncStringContentListDataAllocator aDataAllocator,
+      const nsAString& aString, mozilla::DebugOnly<ContentListType> aType)
+      : nsContentList(aRootNode, aFunc, aDestroyFunc, nullptr),
+#ifdef DEBUG
+        mType(aType),
+#endif
+        mString(aString) {
+    mData = (*aDataAllocator)(aRootNode, &mString);
+    MOZ_ASSERT(mData);
+  }
+
+  void RemoveFromCaches() override { RemoveFromFuncStringHashtable(); }
+  void RemoveFromFuncStringHashtable();
+
+  nsString mString;
+};
+
+class nsCachableElementsByNameNodeList
+    : public nsCacheableFuncStringContentList {
+ public:
+  nsCachableElementsByNameNodeList(
+      nsINode* aRootNode, nsContentListMatchFunc aFunc,
+      nsContentListDestroyFunc aDestroyFunc,
+      nsFuncStringContentListDataAllocator aDataAllocator,
+      const nsAString& aString)
+      : nsCacheableFuncStringContentList(aRootNode, aFunc, aDestroyFunc,
+                                         aDataAllocator, aString, eNodeList) {}
+
+  NS_DECL_NSIMUTATIONOBSERVER_ATTRIBUTECHANGED
+
+  JSObject* WrapObject(JSContext* cx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+#ifdef DEBUG
+  static const ContentListType sType;
+#endif
+};
+
+class nsCacheableFuncStringHTMLCollection
+    : public nsCacheableFuncStringContentList {
+ public:
+  nsCacheableFuncStringHTMLCollection(
+      nsINode* aRootNode, nsContentListMatchFunc aFunc,
+      nsContentListDestroyFunc aDestroyFunc,
+      nsFuncStringContentListDataAllocator aDataAllocator,
+      const nsAString& aString)
+      : nsCacheableFuncStringContentList(aRootNode, aFunc, aDestroyFunc,
+                                         aDataAllocator, aString,
+                                         eHTMLCollection) {}
+
+  JSObject* WrapObject(JSContext* cx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+#ifdef DEBUG
+  static const ContentListType sType;
+#endif
+};
+
+class nsLabelsNodeList final : public nsContentList {
+ public:
+  nsLabelsNodeList(nsINode* aRootNode, nsContentListMatchFunc aFunc,
+                   nsContentListDestroyFunc aDestroyFunc, void* aData)
+      : nsContentList(aRootNode, aFunc, aDestroyFunc, aData) {}
+
+  NS_DECL_NSIMUTATIONOBSERVER_ATTRIBUTECHANGED
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTAPPENDED
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTINSERTED
+  NS_DECL_NSIMUTATIONOBSERVER_CONTENTREMOVED
+
+  JSObject* WrapObject(JSContext* cx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  /**
+   * Reset root, mutation observer, and clear content list
+   * if the root has been changed.
+   *
+   * @param aRootNode The node under which to limit our search.
+   */
+  void MaybeResetRoot(nsINode* aRootNode);
+
+ private:
+  /**
+   * Start searching at the last one if we already have nodes, otherwise
+   * start searching at the root.
+   *
+   * @param aNeededLength The list of length should have when we are
+   *                      done (unless it exhausts the document).
+   * @param aExpectedElementsIfDirty is for debugging only to
+   *        assert that mElements has expected number of entries.
+   */
+  void PopulateSelf(uint32_t aNeededLength,
+                    uint32_t aExpectedElementsIfDirty = 0) override;
+};
+#endif  // nsContentList_h___