Adding upstream version 124.0.1.upstream/124.0.1

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

1 files changed, 2544 insertions, 0 deletions

diff --git a/dom/base/nsINode.h b/dom/base/nsINode.h
new file mode 100644
index 0000000000..ce9fbd55be
--- /dev/null
+++ b/dom/base/nsINode.h
@@ -0,0 +1,2544 @@
+/* -*- 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 nsINode_h___
+#define nsINode_h___
+
+#include "mozilla/DoublyLinkedList.h"
+#include "mozilla/Likely.h"
+#include "mozilla/UniquePtr.h"
+#include "nsCOMPtr.h"              // for member, local
+#include "nsGkAtoms.h"             // for nsGkAtoms::baseURIProperty
+#include "mozilla/dom/NodeInfo.h"  // member (in nsCOMPtr)
+#include "nsIWeakReference.h"
+#include "nsIMutationObserver.h"
+#include "nsNodeInfoManager.h"  // for use in NodePrincipal()
+#include "nsPropertyTable.h"    // for typedefs
+#include "mozilla/ErrorResult.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/dom/EventTarget.h"  // for base class
+#include "js/TypeDecls.h"             // for Handle, Value, JSObject, JSContext
+#include "mozilla/dom/DOMString.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/NodeBinding.h"
+#include "nsTHashtable.h"
+#include <iosfwd>
+
+// Including 'windows.h' will #define GetClassInfo to something else.
+#ifdef XP_WIN
+#  ifdef GetClassInfo
+#    undef GetClassInfo
+#  endif
+#endif
+
+class AttrArray;
+class nsAttrChildContentList;
+template <typename T>
+class nsCOMArray;
+class nsDOMAttributeMap;
+class nsGenericHTMLElement;
+class nsIAnimationObserver;
+class nsIContent;
+class nsIContentSecurityPolicy;
+class nsIFrame;
+class nsIHTMLCollection;
+class nsMultiMutationObserver;
+class nsINode;
+class nsINodeList;
+class nsIPrincipal;
+class nsIURI;
+class nsNodeSupportsWeakRefTearoff;
+class nsDOMMutationObserver;
+class nsRange;
+class nsWindowSizes;
+
+namespace mozilla {
+class EventListenerManager;
+struct StyleSelectorList;
+template <typename T>
+class Maybe;
+class PresShell;
+class TextEditor;
+namespace dom {
+/**
+ * @return true if aChar is what the WHATWG defines as a 'ascii whitespace'.
+ * https://infra.spec.whatwg.org/#ascii-whitespace
+ */
+inline bool IsSpaceCharacter(char16_t aChar) {
+  return aChar == ' ' || aChar == '\t' || aChar == '\n' || aChar == '\r' ||
+         aChar == '\f';
+}
+inline bool IsSpaceCharacter(char aChar) {
+  return aChar == ' ' || aChar == '\t' || aChar == '\n' || aChar == '\r' ||
+         aChar == '\f';
+}
+class AbstractRange;
+class AccessibleNode;
+template <typename T>
+class AncestorsOfTypeIterator;
+struct BoxQuadOptions;
+struct ConvertCoordinateOptions;
+class DocGroup;
+class Document;
+class DocumentFragment;
+class DocumentOrShadowRoot;
+class DOMPoint;
+class DOMQuad;
+class DOMRectReadOnly;
+class Element;
+class EventHandlerNonNull;
+template <typename T>
+class FlatTreeAncestorsOfTypeIterator;
+template <typename T>
+class InclusiveAncestorsOfTypeIterator;
+template <typename T>
+class InclusiveFlatTreeAncestorsOfTypeIterator;
+class LinkStyle;
+class MutationObservers;
+template <typename T>
+class Optional;
+class OwningNodeOrString;
+template <typename>
+class Sequence;
+class ShadowRoot;
+class SVGUseElement;
+class Text;
+class TextOrElementOrDocument;
+struct DOMPointInit;
+struct GetRootNodeOptions;
+enum class CallerType : uint32_t;
+}  // namespace dom
+}  // namespace mozilla
+
+#define NODE_FLAG_BIT(n_) \
+  (nsWrapperCache::FlagsType(1U) << (WRAPPER_CACHE_FLAGS_BITS_USED + (n_)))
+
+enum : uint32_t {
+  // This bit will be set if the node has a listener manager.
+  NODE_HAS_LISTENERMANAGER = NODE_FLAG_BIT(0),
+
+  // Whether this node has had any properties set on it
+  NODE_HAS_PROPERTIES = NODE_FLAG_BIT(1),
+
+  // Whether the node has some ancestor, possibly itself, that is native
+  // anonymous.  This includes ancestors crossing XBL scopes, in cases when an
+  // XBL binding is attached to an element which has a native anonymous
+  // ancestor.  This flag is set-once: once a node has it, it must not be
+  // removed.
+  // NOTE: Should only be used on nsIContent nodes
+  NODE_IS_IN_NATIVE_ANONYMOUS_SUBTREE = NODE_FLAG_BIT(2),
+
+  // Whether this node is the root of a native anonymous (from the perspective
+  // of its parent) subtree.  This flag is set-once: once a node has it, it
+  // must not be removed.
+  // NOTE: Should only be used on nsIContent nodes
+  NODE_IS_NATIVE_ANONYMOUS_ROOT = NODE_FLAG_BIT(3),
+
+  NODE_IS_EDITABLE = NODE_FLAG_BIT(4),
+
+  // Whether the node participates in a shadow tree.
+  NODE_IS_IN_SHADOW_TREE = NODE_FLAG_BIT(5),
+
+  // This node needs to go through frame construction to get a frame (or
+  // undisplayed entry).
+  NODE_NEEDS_FRAME = NODE_FLAG_BIT(6),
+
+  // At least one descendant in the flattened tree has NODE_NEEDS_FRAME set.
+  // This should be set on every node on the flattened tree path between the
+  // node(s) with NODE_NEEDS_FRAME and the root content.
+  NODE_DESCENDANTS_NEED_FRAMES = NODE_FLAG_BIT(7),
+
+  // Set if the node has the accesskey attribute set.
+  NODE_HAS_ACCESSKEY = NODE_FLAG_BIT(8),
+
+  NODE_HAS_BEEN_IN_UA_WIDGET = NODE_FLAG_BIT(9),
+
+  // Set if the node has a nonce value and a header delivered CSP.
+  NODE_HAS_NONCE_AND_HEADER_CSP = NODE_FLAG_BIT(10),
+
+  NODE_KEEPS_DOMARENA = NODE_FLAG_BIT(11),
+
+  NODE_MAY_HAVE_ELEMENT_CHILDREN = NODE_FLAG_BIT(12),
+
+  // Remaining bits are node type specific.
+  NODE_TYPE_SPECIFIC_BITS_OFFSET = 13
+};
+
+// Flags for selectors that persist to the DOM node.
+enum class NodeSelectorFlags : uint32_t {
+  // Node has an :empty or :-moz-only-whitespace selector
+  HasEmptySelector = 1 << 0,
+
+  /// A child of the node has a selector such that any insertion,
+  /// removal, or appending of children requires restyling the parent, if the
+  /// parent is an element. If the parent is the shadow root, the child's
+  /// siblings are restyled.
+  HasSlowSelector = 1 << 1,
+
+  /// A child of the node has a :first-child, :-moz-first-node,
+  /// :only-child, :last-child or :-moz-last-node selector.
+  HasEdgeChildSelector = 1 << 2,
+
+  /// A child of the node has a selector such that any insertion or
+  /// removal of children requires restyling later siblings of that
+  /// element.  Additionally (in this manner it is stronger than
+  /// NODE_HAS_SLOW_SELECTOR), if a child's style changes due to any
+  /// other content tree changes (e.g., the child changes to or from
+  /// matching :empty due to a grandchild insertion or removal), the
+  /// child's later siblings must also be restyled.
+  HasSlowSelectorLaterSiblings = 1 << 3,
+
+  /// HasSlowSelector* was set by the presence of :nth (But not of).
+  HasSlowSelectorNth = 1 << 4,
+
+  /// A child of this node might be matched by :nth-child(.. of <selector>) or
+  /// :nth-last-child(.. of <selector>). If a DOM mutation may have caused the
+  /// selector to either match or no longer match that child, the child's
+  /// siblings are restyled.
+  HasSlowSelectorNthOf = 1 << 5,
+
+  /// All instances of :nth flags.
+  HasSlowSelectorNthAll = HasSlowSelectorNthOf | HasSlowSelectorNth,
+
+  /// Set of selector flags that may trigger a restyle on DOM append, with
+  /// restyle on siblings or a single parent (And perhaps their subtrees).
+  AllSimpleRestyleFlagsForAppend = HasEmptySelector | HasSlowSelector |
+                                   HasEdgeChildSelector | HasSlowSelectorNthAll,
+
+  /// Set of selector flags that may trigger a restyle as a result of any
+  /// DOM mutation.
+  AllSimpleRestyleFlags =
+      AllSimpleRestyleFlagsForAppend | HasSlowSelectorLaterSiblings,
+
+  // This node was evaluated as an anchor for a relative selector.
+  RelativeSelectorAnchor = 1 << 6,
+
+  // This node was evaluated as an anchor for a relative selector, and that
+  // relative selector was not the subject of the overall selector.
+  RelativeSelectorAnchorNonSubject = 1 << 7,
+
+  // This node's sibling(s) performed a relative selector search to this node.
+  RelativeSelectorSearchDirectionSibling = 1 << 8,
+
+  // This node's ancestor(s) performed a relative selector search to this node.
+  RelativeSelectorSearchDirectionAncestor = 1 << 9,
+
+  // This node's sibling(s) and ancestor(s), and/or this node's ancestor's
+  // sibling(s) performed a relative selector search to this node.
+  RelativeSelectorSearchDirectionAncestorSibling =
+      RelativeSelectorSearchDirectionSibling |
+      RelativeSelectorSearchDirectionAncestor,
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(NodeSelectorFlags);
+
+// Make sure we have space for our bits
+#define ASSERT_NODE_FLAGS_SPACE(n)                         \
+  static_assert(WRAPPER_CACHE_FLAGS_BITS_USED + (n) <=     \
+                    sizeof(nsWrapperCache::FlagsType) * 8, \
+                "Not enough space for our bits")
+ASSERT_NODE_FLAGS_SPACE(NODE_TYPE_SPECIFIC_BITS_OFFSET);
+
+/**
+ * Class used to detect unexpected mutations. To use the class create an
+ * nsMutationGuard on the stack before unexpected mutations could occur.
+ * You can then at any time call Mutated to check if any unexpected mutations
+ * have occurred.
+ */
+class nsMutationGuard {
+ public:
+  nsMutationGuard() { mStartingGeneration = sGeneration; }
+
+  /**
+   * Returns true if any unexpected mutations have occurred. You can pass in
+   * an 8-bit ignore count to ignore a number of expected mutations.
+   *
+   * We don't need to care about overflow because subtraction of uint64_t's is
+   * finding the difference between two elements of the group Z < 2^64.  Once
+   * we know the difference between two elements we only need to check that is
+   * less than the given number of mutations to know less than that many
+   * mutations occured.  Assuming constant 1ns mutations it would take 584
+   * years for sGeneration to fully wrap around so we can ignore a guard living
+   * through a full wrap around.
+   */
+  bool Mutated(uint8_t aIgnoreCount) {
+    return (sGeneration - mStartingGeneration) > aIgnoreCount;
+  }
+
+  // This function should be called whenever a mutation that we want to keep
+  // track of happen. For now this is only done when children are added or
+  // removed, but we might do it for attribute changes too in the future.
+  static void DidMutate() { sGeneration++; }
+
+ private:
+  // This is the value sGeneration had when the guard was constructed.
+  uint64_t mStartingGeneration;
+
+  // This value is incremented on every mutation, for the life of the process.
+  static uint64_t sGeneration;
+};
+
+/**
+ * A class that implements nsIWeakReference
+ */
+class nsNodeWeakReference final : public nsIWeakReference {
+ public:
+  explicit nsNodeWeakReference(nsINode* aNode);
+
+  // nsISupports
+  NS_DECL_ISUPPORTS
+
+  // nsIWeakReference
+  NS_DECL_NSIWEAKREFERENCE
+
+  void NoticeNodeDestruction() { mObject = nullptr; }
+
+ private:
+  ~nsNodeWeakReference();
+};
+
+// This should be used for any nsINode sub-class that has fields of its own
+// that it needs to measure; any sub-class that doesn't use it will inherit
+// AddSizeOfExcludingThis from its super-class. AddSizeOfIncludingThis() need
+// not be defined, it is inherited from nsINode.
+#define NS_DECL_ADDSIZEOFEXCLUDINGTHIS                       \
+  virtual void AddSizeOfExcludingThis(nsWindowSizes& aSizes, \
+                                      size_t* aNodeSize) const override;
+
+// IID for the nsINode interface
+// Must be kept in sync with xpcom/rust/xpcom/src/interfaces/nonidl.rs
+#define NS_INODE_IID                                 \
+  {                                                  \
+    0x70ba4547, 0x7699, 0x44fc, {                    \
+      0xb3, 0x20, 0x52, 0xdb, 0xe3, 0xd1, 0xf9, 0x0a \
+    }                                                \
+  }
+
+/**
+ * An internal interface that abstracts some DOMNode-related parts that both
+ * nsIContent and Document share.  An instance of this interface has a list
+ * of nsIContent children and provides access to them.
+ */
+class nsINode : public mozilla::dom::EventTarget {
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  void AssertInvariantsOnNodeInfoChange();
+#endif
+ public:
+  using BoxQuadOptions = mozilla::dom::BoxQuadOptions;
+  using ConvertCoordinateOptions = mozilla::dom::ConvertCoordinateOptions;
+  using DocGroup = mozilla::dom::DocGroup;
+  using Document = mozilla::dom::Document;
+  using DOMPoint = mozilla::dom::DOMPoint;
+  using DOMPointInit = mozilla::dom::DOMPointInit;
+  using DOMQuad = mozilla::dom::DOMQuad;
+  using DOMRectReadOnly = mozilla::dom::DOMRectReadOnly;
+  using OwningNodeOrString = mozilla::dom::OwningNodeOrString;
+  using TextOrElementOrDocument = mozilla::dom::TextOrElementOrDocument;
+  using CallerType = mozilla::dom::CallerType;
+  using ErrorResult = mozilla::ErrorResult;
+
+  // XXXbz Maybe we should codegen a class holding these constants and
+  // inherit from it...
+  static const auto ELEMENT_NODE = mozilla::dom::Node_Binding::ELEMENT_NODE;
+  static const auto ATTRIBUTE_NODE = mozilla::dom::Node_Binding::ATTRIBUTE_NODE;
+  static const auto TEXT_NODE = mozilla::dom::Node_Binding::TEXT_NODE;
+  static const auto CDATA_SECTION_NODE =
+      mozilla::dom::Node_Binding::CDATA_SECTION_NODE;
+  static const auto ENTITY_REFERENCE_NODE =
+      mozilla::dom::Node_Binding::ENTITY_REFERENCE_NODE;
+  static const auto ENTITY_NODE = mozilla::dom::Node_Binding::ENTITY_NODE;
+  static const auto PROCESSING_INSTRUCTION_NODE =
+      mozilla::dom::Node_Binding::PROCESSING_INSTRUCTION_NODE;
+  static const auto COMMENT_NODE = mozilla::dom::Node_Binding::COMMENT_NODE;
+  static const auto DOCUMENT_NODE = mozilla::dom::Node_Binding::DOCUMENT_NODE;
+  static const auto DOCUMENT_TYPE_NODE =
+      mozilla::dom::Node_Binding::DOCUMENT_TYPE_NODE;
+  static const auto DOCUMENT_FRAGMENT_NODE =
+      mozilla::dom::Node_Binding::DOCUMENT_FRAGMENT_NODE;
+  static const auto NOTATION_NODE = mozilla::dom::Node_Binding::NOTATION_NODE;
+  static const auto MAX_NODE_TYPE = NOTATION_NODE;
+
+  void* operator new(size_t aSize, nsNodeInfoManager* aManager);
+  void* operator new(size_t aSize) = delete;
+  void operator delete(void* aPtr);
+
+  template <class T>
+  using Sequence = mozilla::dom::Sequence<T>;
+
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_INODE_IID)
+
+  // The |aNodeSize| outparam on this function is where the actual node size
+  // value is put. It gets added to the appropriate value within |aSizes| by
+  // AddSizeOfNodeTree().
+  //
+  // Among the sub-classes that inherit (directly or indirectly) from nsINode,
+  // measurement of the following members may be added later if DMD finds it is
+  // worthwhile:
+  // - nsGenericHTMLElement:  mForm, mFieldSet
+  // - nsGenericHTMLFrameElement: mFrameLoader (bug 672539)
+  // - HTMLBodyElement:       mContentStyleRule
+  // - HTMLDataListElement:   mOptions
+  // - HTMLFieldSetElement:   mElements, mDependentElements, mFirstLegend
+  // - HTMLFormElement:       many!
+  // - HTMLFrameSetElement:   mRowSpecs, mColSpecs
+  // - HTMLInputElement:      mInputData, mFiles, mFileList, mStaticDocfileList
+  // - nsHTMLMapElement:      mAreas
+  // - HTMLMediaElement:      many!
+  // - nsHTMLOutputElement:   mDefaultValue, mTokenList
+  // - nsHTMLRowElement:      mCells
+  // - nsHTMLSelectElement:   mOptions, mRestoreState
+  // - nsHTMLTableElement:    mTBodies, mRows, mTableInheritedAttributes
+  // - nsHTMLTableSectionElement: mRows
+  // - nsHTMLTextAreaElement: mControllers, mState
+  //
+  // The following members don't need to be measured:
+  // - nsIContent: mPrimaryFrame, because it's non-owning and measured elsewhere
+  //
+  virtual void AddSizeOfExcludingThis(nsWindowSizes& aSizes,
+                                      size_t* aNodeSize) const;
+
+  // SizeOfIncludingThis doesn't need to be overridden by sub-classes because
+  // sub-classes of nsINode are guaranteed to be laid out in memory in such a
+  // way that |this| points to the start of the allocated object, even in
+  // methods of nsINode's sub-classes, so aSizes.mState.mMallocSizeOf(this) is
+  // always safe to call no matter which object it was invoked on.
+  void AddSizeOfIncludingThis(nsWindowSizes& aSizes, size_t* aNodeSize) const;
+
+  friend class nsNodeWeakReference;
+  friend class nsNodeSupportsWeakRefTearoff;
+  friend class AttrArray;
+
+#ifdef MOZILLA_INTERNAL_API
+  explicit nsINode(already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo);
+#endif
+
+  virtual ~nsINode();
+
+  bool IsContainerNode() const {
+    return IsElement() || IsDocument() || IsDocumentFragment();
+  }
+
+  /**
+   * Returns true if the node is a HTMLTemplate element.
+   */
+  bool IsTemplateElement() const { return IsHTMLElement(nsGkAtoms::_template); }
+
+  bool IsSlotable() const { return IsElement() || IsText(); }
+
+  /**
+   * Returns true if this is a document node.
+   */
+  bool IsDocument() const {
+    // One less pointer-chase than checking NodeType().
+    return !GetParentNode() && IsInUncomposedDoc();
+  }
+
+  /**
+   * Return this node as a document. Asserts IsDocument().
+   *
+   * This is defined inline in Document.h.
+   */
+  inline Document* AsDocument();
+  inline const Document* AsDocument() const;
+
+  /**
+   * Returns true if this is a document fragment node.
+   */
+  bool IsDocumentFragment() const {
+    return NodeType() == DOCUMENT_FRAGMENT_NODE;
+  }
+
+  virtual bool IsHTMLFormControlElement() const { return false; }
+
+  /**
+   * https://dom.spec.whatwg.org/#concept-tree-inclusive-descendant
+   *
+   * @param aNode must not be nullptr.
+   */
+  bool IsInclusiveDescendantOf(const nsINode* aNode) const;
+
+  /**
+   * https://dom.spec.whatwg.org/#concept-shadow-including-inclusive-descendant
+   *
+   * @param aNode must not be nullptr.
+   */
+  bool IsShadowIncludingInclusiveDescendantOf(const nsINode* aNode) const;
+
+  /**
+   * Returns true if the given node is this node or one of its descendants
+   * in the "flat tree."
+   *
+   * @param aNode must not be nullptr.
+   */
+  bool IsInclusiveFlatTreeDescendantOf(const nsINode* aNode) const;
+
+  /**
+   * Return this node as a document fragment. Asserts IsDocumentFragment().
+   *
+   * This is defined inline in DocumentFragment.h.
+   */
+  inline mozilla::dom::DocumentFragment* AsDocumentFragment();
+  inline const mozilla::dom::DocumentFragment* AsDocumentFragment() const;
+
+  JSObject* WrapObject(JSContext*, JS::Handle<JSObject*> aGivenProto) final;
+
+  /**
+   * Hook for constructing JS::ubi::Concrete specializations for memory
+   * reporting. Specializations are defined in NodeUbiReporting.h.
+   */
+  virtual void ConstructUbiNode(void* storage) = 0;
+
+  /**
+   * returns true if we are in priviliged code or
+   * layout.css.getBoxQuads.enabled == true.
+   */
+  static bool HasBoxQuadsSupport(JSContext* aCx, JSObject* /* unused */);
+
+ protected:
+  /**
+   * WrapNode is called from WrapObject to actually wrap this node, WrapObject
+   * does some additional checks and fix-up that's common to all nodes. WrapNode
+   * should just call the DOM binding's Wrap function.
+   *
+   * aGivenProto is the prototype to use (or null if the default one should be
+   * used) and should just be passed directly on to the DOM binding's Wrap
+   * function.
+   */
+  virtual JSObject* WrapNode(JSContext* aCx,
+                             JS::Handle<JSObject*> aGivenProto) = 0;
+
+ public:
+  mozilla::dom::ParentObject GetParentObject()
+      const;  // Implemented in Document.h
+
+  /**
+   * Returns the first child of a node or the first child of
+   * a template element's content if the provided node is a
+   * template element.
+   */
+  nsIContent* GetFirstChildOfTemplateOrNode();
+
+  /**
+   * Return the scope chain parent for this node, for use in things
+   * like event handler compilation.  Returning null means to use the
+   * global object as the scope chain parent.
+   */
+  virtual nsINode* GetScopeChainParent() const;
+
+  MOZ_CAN_RUN_SCRIPT mozilla::dom::Element* GetParentFlexElement();
+
+  /**
+   * Returns the nearest inclusive open popover for a given node, see
+   * https://html.spec.whatwg.org/multipage/popover.html#nearest-inclusive-open-popover
+   */
+  mozilla::dom::Element* GetNearestInclusiveOpenPopover() const;
+
+  /**
+   * https://html.spec.whatwg.org/multipage/popover.html#nearest-inclusive-target-popover-for-invoker
+   */
+  mozilla::dom::Element* GetNearestInclusiveTargetPopoverForInvoker() const;
+
+  /**
+   * https://html.spec.whatwg.org/multipage/popover.html#popover-target-element
+   */
+  nsGenericHTMLElement* GetEffectivePopoverTargetElement() const;
+
+  /**
+   * https://html.spec.whatwg.org/multipage/popover.html#topmost-clicked-popover
+   */
+  mozilla::dom::Element* GetTopmostClickedPopover() const;
+
+  bool IsNode() const final { return true; }
+
+  NS_IMPL_FROMEVENTTARGET_HELPER(nsINode, IsNode())
+
+  /**
+   * Return whether the node is an Element node. Faster than using `NodeType()`.
+   */
+  bool IsElement() const { return GetBoolFlag(NodeIsElement); }
+
+  virtual bool IsTextControlElement() const { return false; }
+  virtual bool IsGenericHTMLFormControlElementWithState() const {
+    return false;
+  }
+
+  // Returns non-null if this element subclasses `LinkStyle`.
+  virtual const mozilla::dom::LinkStyle* AsLinkStyle() const { return nullptr; }
+  mozilla::dom::LinkStyle* AsLinkStyle() {
+    return const_cast<mozilla::dom::LinkStyle*>(
+        static_cast<const nsINode*>(this)->AsLinkStyle());
+  }
+
+  /**
+   * Return this node as an Element.  Should only be used for nodes
+   * for which IsElement() is true.  This is defined inline in Element.h.
+   */
+  inline mozilla::dom::Element* AsElement();
+  inline const mozilla::dom::Element* AsElement() const;
+
+  /**
+   * Return whether the node is an nsStyledElement instance or not.
+   */
+  virtual bool IsStyledElement() const { return false; }
+
+  /**
+   * Return this node as nsIContent.  Should only be used for nodes for which
+   * IsContent() is true.
+   *
+   * The assertion in nsIContent's constructor makes this safe.
+   */
+  nsIContent* AsContent() {
+    MOZ_ASSERT(IsContent());
+    return reinterpret_cast<nsIContent*>(this);
+  }
+  const nsIContent* AsContent() const {
+    MOZ_ASSERT(IsContent());
+    return reinterpret_cast<const nsIContent*>(this);
+  }
+
+  /*
+   * Return whether the node is a Text node (which might be an actual
+   * textnode, or might be a CDATA section).
+   */
+  bool IsText() const {
+    uint32_t nodeType = NodeType();
+    return nodeType == TEXT_NODE || nodeType == CDATA_SECTION_NODE;
+  }
+
+  /**
+   * Return this node as Text if it is one, otherwise null.  This is defined
+   * inline in Text.h.
+   */
+  inline mozilla::dom::Text* GetAsText();
+  inline const mozilla::dom::Text* GetAsText() const;
+
+  /**
+   * Return this node as Text.  Asserts IsText().  This is defined inline in
+   * Text.h.
+   */
+  inline mozilla::dom::Text* AsText();
+  inline const mozilla::dom::Text* AsText() const;
+
+  /*
+   * Return whether the node is a ProcessingInstruction node.
+   */
+  bool IsProcessingInstruction() const {
+    return NodeType() == PROCESSING_INSTRUCTION_NODE;
+  }
+
+  /*
+   * Return whether the node is a CharacterData node (text, cdata,
+   * comment, processing instruction)
+   */
+  bool IsCharacterData() const {
+    uint32_t nodeType = NodeType();
+    return nodeType == TEXT_NODE || nodeType == CDATA_SECTION_NODE ||
+           nodeType == PROCESSING_INSTRUCTION_NODE || nodeType == COMMENT_NODE;
+  }
+
+  /**
+   * Return whether the node is a Comment node.
+   */
+  bool IsComment() const { return NodeType() == COMMENT_NODE; }
+
+  /**
+   * Return whether the node is an Attr node.
+   */
+  bool IsAttr() const { return NodeType() == ATTRIBUTE_NODE; }
+
+  /**
+   * Return if this node has any children.
+   */
+  bool HasChildren() const { return !!mFirstChild; }
+
+  /**
+   * Get the number of children
+   * @return the number of children
+   */
+  uint32_t GetChildCount() const { return mChildCount; }
+
+  /**
+   * NOTE: this function is going to be removed soon (hopefully!) Don't use it
+   * in new code.
+   *
+   * Get a child by index
+   * @param aIndex the index of the child to get
+   * @return the child, or null if index out of bounds
+   */
+  nsIContent* GetChildAt_Deprecated(uint32_t aIndex) const;
+
+  /**
+   * Get the index of a child within this content.
+   *
+   * @param aPossibleChild the child to get the index of.
+   * @return the index of the child, or Nothing if not a child. Be aware that
+   *         anonymous children (e.g. a <div> child of an <input> element) will
+   *         result in Nothing.
+   *
+   * If the return value is Some, then calling GetChildAt_Deprecated() with
+   * that value will return aPossibleChild.
+   */
+  mozilla::Maybe<uint32_t> ComputeIndexOf(const nsINode* aPossibleChild) const;
+
+  /**
+   * Get the index of a child within this content's flat tree children.
+   *
+   * @param aPossibleChild the child to get the index of.
+   * @return the index of the child, or Nothing if not a child. Be aware that
+   *         anonymous children (e.g. a <div> child of an <input> element) will
+   *         result in Nothing.
+   */
+  mozilla::Maybe<uint32_t> ComputeFlatTreeIndexOf(
+      const nsINode* aPossibleChild) const;
+
+  /**
+   * Get the index of this within parent node (ComputeIndexInParentNode) or
+   * parent content (nsIContent) node (ComputeIndexInParentContent).
+   *
+   * @return the index of this node in the parent, or Nothing there is no
+   *         parent (content) node or the parent does not have this node anymore
+   *         (e.g., being removed from the parent). Be aware that anonymous
+   *         children (e.g. a <div> child of an <input> element) will result in
+   *         Nothing.
+   *
+   * If the return value is Some, then calling GetChildAt_Deprecated() with
+   * that value will return this.
+   */
+  mozilla::Maybe<uint32_t> ComputeIndexInParentNode() const;
+  mozilla::Maybe<uint32_t> ComputeIndexInParentContent() const;
+
+  /**
+   * Get the index of a child within this content.
+   *
+   * @param aPossibleChild the child to get the index of.
+   * @return the index of the child, or -1 if not a child. Be aware that
+   *         anonymous children (e.g. a <div> child of an <input> element) will
+   *         result in -1.
+   *
+   * If the return value is not -1, then calling GetChildAt_Deprecated() with
+   * that value will return aPossibleChild.
+   */
+  int32_t ComputeIndexOf_Deprecated(const nsINode* aPossibleChild) const;
+
+  /**
+   * Returns the "node document" of this node.
+   *
+   * https://dom.spec.whatwg.org/#concept-node-document
+   *
+   * Note that in the case that this node is a document node this method
+   * will return |this|.  That is different to the Node.ownerDocument DOM
+   * attribute (implemented by nsINode::GetOwnerDocument) which is specified to
+   * be null in that case:
+   *
+   * https://dom.spec.whatwg.org/#dom-node-ownerdocument
+   *
+   * For all other cases OwnerDoc and GetOwnerDocument behave identically.
+   */
+  Document* OwnerDoc() const MOZ_NONNULL_RETURN {
+    return mNodeInfo->GetDocument();
+  }
+
+  /**
+   * Return the "owner document" of this node as an nsINode*.  Implemented
+   * in Document.h.
+   */
+  inline nsINode* OwnerDocAsNode() const MOZ_NONNULL_RETURN;
+
+  /**
+   * Returns true if the content has an ancestor that is a document.
+   *
+   * @return whether this content is in a document tree
+   */
+  bool IsInUncomposedDoc() const { return GetBoolFlag(IsInDocument); }
+
+  /**
+   * Get the document that this content is currently in, if any. This will be
+   * null if the content has no ancestor that is a document.
+   *
+   * @return the current document
+   */
+
+  Document* GetUncomposedDoc() const {
+    return IsInUncomposedDoc() ? OwnerDoc() : nullptr;
+  }
+
+  /**
+   * Returns true if we're connected, and thus GetComposedDoc() would return a
+   * non-null value.
+   */
+  bool IsInComposedDoc() const { return GetBoolFlag(IsConnected); }
+
+  /**
+   * This method returns the owner document if the node is connected to it
+   * (as defined in the DOM spec), otherwise it returns null.
+   * In other words, returns non-null even in the case the node is in
+   * Shadow DOM, if there is a possibly shadow boundary crossing path from
+   * the node to its owner document.
+   */
+  Document* GetComposedDoc() const {
+    return IsInComposedDoc() ? OwnerDoc() : nullptr;
+  }
+
+  /**
+   * Returns OwnerDoc() if the node is in uncomposed document and ShadowRoot if
+   * the node is in Shadow DOM.
+   */
+  mozilla::dom::DocumentOrShadowRoot* GetContainingDocumentOrShadowRoot() const;
+
+  /**
+   * Returns OwnerDoc() if the node is in uncomposed document and ShadowRoot if
+   * the node is in Shadow DOM and is in composed document.
+   */
+  mozilla::dom::DocumentOrShadowRoot* GetUncomposedDocOrConnectedShadowRoot()
+      const;
+
+  /**
+   * To be called when reference count of the node drops to zero.
+   */
+  void LastRelease();
+
+  /**
+   * The values returned by this function are the ones defined for
+   * Node.nodeType
+   */
+  uint16_t NodeType() const { return mNodeInfo->NodeType(); }
+  const nsString& NodeName() const { return mNodeInfo->NodeName(); }
+  const nsString& LocalName() const { return mNodeInfo->LocalName(); }
+
+  /**
+   * Get the NodeInfo for this element
+   * @return the nodes node info
+   */
+  inline mozilla::dom::NodeInfo* NodeInfo() const { return mNodeInfo; }
+
+  /**
+   * Called when we have been adopted, and the information of the
+   * node has been changed.
+   *
+   * The new document can be reached via OwnerDoc().
+   *
+   * If you override this method,
+   * please call up to the parent NodeInfoChanged.
+   *
+   * If you change this, change also the similar method in Link.
+   */
+  virtual void NodeInfoChanged(Document* aOldDoc) {
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+    AssertInvariantsOnNodeInfoChange();
+#endif
+  }
+
+  inline bool IsInNamespace(int32_t aNamespace) const {
+    return mNodeInfo->NamespaceID() == aNamespace;
+  }
+
+  /**
+   * Returns the DocGroup of the "node document" of this node.
+   */
+  DocGroup* GetDocGroup() const;
+
+  /**
+   * Print a debugger friendly descriptor of this element. This will describe
+   * the position of this element in the document.
+   */
+  friend std::ostream& operator<<(std::ostream& aStream, const nsINode& aNode);
+
+ protected:
+  // These 2 methods are useful for the recursive templates IsHTMLElement,
+  // IsSVGElement, etc.
+  inline bool IsNodeInternal() const { return false; }
+
+  template <typename First, typename... Args>
+  inline bool IsNodeInternal(First aFirst, Args... aArgs) const {
+    return mNodeInfo->Equals(aFirst) || IsNodeInternal(aArgs...);
+  }
+
+ public:
+  inline bool IsHTMLElement() const {
+    return IsElement() && IsInNamespace(kNameSpaceID_XHTML);
+  }
+
+  inline bool IsHTMLElement(const nsAtom* aTag) const {
+    return IsElement() && mNodeInfo->Equals(aTag, kNameSpaceID_XHTML);
+  }
+
+  template <typename First, typename... Args>
+  inline bool IsAnyOfHTMLElements(First aFirst, Args... aArgs) const {
+    return IsHTMLElement() && IsNodeInternal(aFirst, aArgs...);
+  }
+
+  inline bool IsSVGElement() const {
+    return IsElement() && IsInNamespace(kNameSpaceID_SVG);
+  }
+
+  inline bool IsSVGElement(const nsAtom* aTag) const {
+    return IsElement() && mNodeInfo->Equals(aTag, kNameSpaceID_SVG);
+  }
+
+  template <typename First, typename... Args>
+  inline bool IsAnyOfSVGElements(First aFirst, Args... aArgs) const {
+    return IsSVGElement() && IsNodeInternal(aFirst, aArgs...);
+  }
+
+  virtual bool IsSVGAnimationElement() const { return false; }
+  virtual bool IsSVGComponentTransferFunctionElement() const { return false; }
+  virtual bool IsSVGFilterPrimitiveElement() const { return false; }
+  virtual bool IsSVGFilterPrimitiveChildElement() const { return false; }
+  virtual bool IsSVGGeometryElement() const { return false; }
+  virtual bool IsSVGGraphicsElement() const { return false; }
+
+  inline bool IsXULElement() const {
+    return IsElement() && IsInNamespace(kNameSpaceID_XUL);
+  }
+
+  inline bool IsXULElement(const nsAtom* aTag) const {
+    return IsElement() && mNodeInfo->Equals(aTag, kNameSpaceID_XUL);
+  }
+
+  template <typename First, typename... Args>
+  inline bool IsAnyOfXULElements(First aFirst, Args... aArgs) const {
+    return IsXULElement() && IsNodeInternal(aFirst, aArgs...);
+  }
+
+  inline bool IsMathMLElement() const {
+    return IsElement() && IsInNamespace(kNameSpaceID_MathML);
+  }
+
+  inline bool IsMathMLElement(const nsAtom* aTag) const {
+    return IsElement() && mNodeInfo->Equals(aTag, kNameSpaceID_MathML);
+  }
+
+  template <typename First, typename... Args>
+  inline bool IsAnyOfMathMLElements(First aFirst, Args... aArgs) const {
+    return IsMathMLElement() && IsNodeInternal(aFirst, aArgs...);
+  }
+
+  bool IsShadowRoot() const {
+    const bool isShadowRoot = IsInShadowTree() && !GetParentNode();
+    MOZ_ASSERT_IF(isShadowRoot, IsDocumentFragment());
+    return isShadowRoot;
+  }
+
+  bool IsHTMLHeadingElement() const {
+    return IsAnyOfHTMLElements(nsGkAtoms::h1, nsGkAtoms::h2, nsGkAtoms::h3,
+                               nsGkAtoms::h4, nsGkAtoms::h5, nsGkAtoms::h6);
+  }
+
+  /**
+   * Check whether the conditional processing attributes other than
+   * systemLanguage "return true" if they apply to and are specified
+   * on the given SVG element. Returns true if this element should be
+   * rendered, false if it should not.
+   */
+  virtual bool PassesConditionalProcessingTests() const { return true; }
+
+  /**
+   * Insert a content node before another or at the end.
+   * This method handles calling BindToTree on the child appropriately.
+   *
+   * @param aKid the content to insert
+   * @param aBeforeThis an existing node. Use nullptr if you want to
+   *        add aKid at the end.
+   * @param aNotify whether to notify the document (current document for
+   *        nsIContent, and |this| for Document) that the insert has occurred
+   * @param aRv The error, if any.
+   *        Throw NS_ERROR_DOM_HIERARCHY_REQUEST_ERR if one attempts to have
+   *        more than one element node as a child of a document.  Doing this
+   *        will also assert -- you shouldn't be doing it!  Check with
+   *        Document::GetRootElement() first if you're not sure.  Apart from
+   *        this one constraint, this doesn't do any checking on whether aKid is
+   *        a valid child of |this|.
+   *        Throw NS_ERROR_OUT_OF_MEMORY in some cases (from BindToTree).
+   */
+  virtual void InsertChildBefore(nsIContent* aKid, nsIContent* aBeforeThis,
+                                 bool aNotify, mozilla::ErrorResult& aRv);
+
+  /**
+   * Append a content node to the end of the child list.  This method handles
+   * calling BindToTree on the child appropriately.
+   *
+   * @param aKid the content to append
+   * @param aNotify whether to notify the document (current document for
+   *        nsIContent, and |this| for Document) that the append has occurred
+   * @param aRv The error, if any.
+   *        Throw NS_ERROR_DOM_HIERARCHY_REQUEST_ERR if one attempts to have
+   *        more than one element node as a child of a document.  Doing this
+   *        will also assert -- you shouldn't be doing it!  Check with
+   *        Document::GetRootElement() first if you're not sure.  Apart from
+   *        this one constraint, this doesn't do any checking on whether aKid is
+   *        a valid child of |this|.
+   *        Throw NS_ERROR_OUT_OF_MEMORY in some cases (from BindToTree).
+   */
+  void AppendChildTo(nsIContent* aKid, bool aNotify,
+                     mozilla::ErrorResult& aRv) {
+    InsertChildBefore(aKid, nullptr, aNotify, aRv);
+  }
+
+  /**
+   * Remove a child from this node.  This method handles calling UnbindFromTree
+   * on the child appropriately.
+   *
+   * @param aKid the content to remove
+   * @param aNotify whether to notify the document (current document for
+   *        nsIContent, and |this| for Document) that the remove has occurred
+   */
+  virtual void RemoveChildNode(nsIContent* aKid, bool aNotify);
+
+  /**
+   * Get a property associated with this node.
+   *
+   * @param aPropertyName  name of property to get.
+   * @param aStatus        out parameter for storing resulting status.
+   *                       Set to NS_PROPTABLE_PROP_NOT_THERE if the property
+   *                       is not set.
+   * @return               the property. Null if the property is not set
+   *                       (though a null return value does not imply the
+   *                       property was not set, i.e. it can be set to null).
+   */
+  void* GetProperty(const nsAtom* aPropertyName,
+                    nsresult* aStatus = nullptr) const;
+
+  /**
+   * Set a property to be associated with this node. This will overwrite an
+   * existing value if one exists. The existing value is destroyed using the
+   * destructor function given when that value was set.
+   *
+   * @param aPropertyName  name of property to set.
+   * @param aValue         new value of property.
+   * @param aDtor          destructor function to be used when this property
+   *                       is destroyed.
+   * @param aTransfer      if true the property will not be deleted when the
+   *                       ownerDocument of the node changes, if false it
+   *                       will be deleted.
+   *
+   * @return NS_PROPTABLE_PROP_OVERWRITTEN (success value) if the property
+   *                                       was already set
+   * @throws NS_ERROR_OUT_OF_MEMORY if that occurs
+   */
+  nsresult SetProperty(nsAtom* aPropertyName, void* aValue,
+                       NSPropertyDtorFunc aDtor = nullptr,
+                       bool aTransfer = false);
+
+  /**
+   * A generic destructor for property values allocated with new.
+   */
+  template <class T>
+  static void DeleteProperty(void*, nsAtom*, void* aPropertyValue, void*) {
+    delete static_cast<T*>(aPropertyValue);
+  }
+
+  /**
+   * Removes a property associated with this node. The value is destroyed using
+   * the destruction function given when that value was set.
+   *
+   * @param aPropertyName  name of property to destroy.
+   */
+  void RemoveProperty(const nsAtom* aPropertyName);
+
+  /**
+   * Take a property associated with this node. The value will not be destroyed
+   * but rather returned. It is the caller's responsibility to destroy the value
+   * after that point.
+   *
+   * @param aPropertyName  name of property to unset.
+   * @param aStatus        out parameter for storing resulting status.
+   *                       Set to NS_PROPTABLE_PROP_NOT_THERE if the property
+   *                       is not set.
+   * @return               the property. Null if the property is not set
+   *                       (though a null return value does not imply the
+   *                       property was not set, i.e. it can be set to null).
+   */
+  void* TakeProperty(const nsAtom* aPropertyName, nsresult* aStatus = nullptr);
+
+  bool HasProperties() const { return HasFlag(NODE_HAS_PROPERTIES); }
+
+  /**
+   * Return the principal of this node.  This is guaranteed to never be a null
+   * pointer.
+   */
+  nsIPrincipal* NodePrincipal() const {
+    return mNodeInfo->NodeInfoManager()->DocumentPrincipal();
+  }
+
+  /**
+   * Return the CSP of this node's document, if any.
+   */
+  nsIContentSecurityPolicy* GetCsp() const;
+
+  /**
+   * Get the parent nsIContent for this node.
+   * @return the parent, or null if no parent or the parent is not an nsIContent
+   */
+  nsIContent* GetParent() const {
+    return MOZ_LIKELY(GetBoolFlag(ParentIsContent)) ? mParent->AsContent()
+                                                    : nullptr;
+  }
+
+  /**
+   * Get the parent nsINode for this node. This can be either an nsIContent, a
+   * Document or an Attr.
+   * @return the parent node
+   */
+  nsINode* GetParentNode() const { return mParent; }
+
+ private:
+  nsIContent* DoGetShadowHost() const;
+
+ public:
+  nsINode* GetParentOrShadowHostNode() const {
+    if (MOZ_LIKELY(mParent)) {
+      return mParent;
+    }
+    // We could put this in nsIContentInlines.h or such to avoid this
+    // reinterpret_cast, but it doesn't seem worth it.
+    return IsInShadowTree() ? reinterpret_cast<nsINode*>(DoGetShadowHost())
+                            : nullptr;
+  }
+
+  enum FlattenedParentType { eNotForStyle, eForStyle };
+
+  /**
+   * Returns the node that is the parent of this node in the flattened
+   * tree. This differs from the normal parent if the node is filtered
+   * into an insertion point, or if the node is a direct child of a
+   * shadow root.
+   *
+   * @return the flattened tree parent
+   */
+  inline nsINode* GetFlattenedTreeParentNode() const;
+
+  nsINode* GetFlattenedTreeParentNodeNonInline() const;
+
+  /**
+   * Like GetFlattenedTreeParentNode, but returns the document for any native
+   * anonymous content that was generated for ancestor frames of the document
+   * element's primary frame, such as scrollbar elements created by the root
+   * scroll frame.
+   */
+  inline nsINode* GetFlattenedTreeParentNodeForStyle() const;
+
+  inline mozilla::dom::Element* GetFlattenedTreeParentElement() const;
+  inline mozilla::dom::Element* GetFlattenedTreeParentElementForStyle() const;
+
+  /**
+   * Get the parent nsINode for this node if it is an Element.
+   *
+   * Defined inline in Element.h
+   *
+   * @return the parent node
+   */
+  inline mozilla::dom::Element* GetParentElement() const;
+
+  /**
+   * Get the parent Element of this node, traversing over a ShadowRoot
+   * to its host if necessary.
+   */
+  mozilla::dom::Element* GetParentElementCrossingShadowRoot() const;
+
+  /**
+   * Get closest element node for the node.  Meaning that if the node is an
+   * element node, returns itself.  Otherwise, returns parent element or null.
+   */
+  inline mozilla::dom::Element* GetAsElementOrParentElement() const;
+
+  /**
+   * Get the root of the subtree this node belongs to.  This never returns
+   * null.  It may return 'this' (e.g. for document nodes, and nodes that
+   * are the roots of disconnected subtrees).
+   */
+  nsINode* SubtreeRoot() const;
+
+  /*
+   * Get context object's shadow-including root if options's composed is true,
+   * and context object's root otherwise.
+   */
+  nsINode* GetRootNode(const mozilla::dom::GetRootNodeOptions& aOptions);
+
+  virtual mozilla::EventListenerManager* GetExistingListenerManager()
+      const override;
+  virtual mozilla::EventListenerManager* GetOrCreateListenerManager() override;
+
+  mozilla::Maybe<mozilla::dom::EventCallbackDebuggerNotificationType>
+  GetDebuggerNotificationType() const override;
+
+  bool ComputeDefaultWantsUntrusted(mozilla::ErrorResult& aRv) final;
+
+  virtual bool IsApzAware() const override;
+
+  virtual nsPIDOMWindowOuter* GetOwnerGlobalForBindingsInternal() override;
+  virtual nsIGlobalObject* GetOwnerGlobal() const override;
+
+  using mozilla::dom::EventTarget::DispatchEvent;
+  // TODO: Convert this to MOZ_CAN_RUN_SCRIPT (bug 1415230)
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY bool DispatchEvent(
+      mozilla::dom::Event& aEvent, mozilla::dom::CallerType aCallerType,
+      mozilla::ErrorResult& aRv) override;
+
+  MOZ_CAN_RUN_SCRIPT
+  nsresult PostHandleEvent(mozilla::EventChainPostVisitor& aVisitor) override;
+
+  /**
+   * Adds a mutation observer to be notified when this node, or any of its
+   * descendants, are modified. The node will hold a weak reference to the
+   * observer, which means that it is the responsibility of the observer to
+   * remove itself in case it dies before the node.  If an observer is added
+   * while observers are being notified, it may also be notified.  In general,
+   * adding observers while inside a notification is not a good idea.  An
+   * observer that is already observing the node must not be added without
+   * being removed first.
+   *
+   * For mutation observers that implement nsIAnimationObserver, use
+   * AddAnimationObserver instead.
+   */
+  void AddMutationObserver(nsIMutationObserver* aMutationObserver) {
+    nsSlots* s = Slots();
+    if (aMutationObserver) {
+      NS_ASSERTION(!s->mMutationObservers.contains(aMutationObserver),
+                   "Observer already in the list");
+
+      s->mMutationObservers.pushBack(aMutationObserver);
+    }
+  }
+
+  void AddMutationObserver(nsMultiMutationObserver* aMultiMutationObserver);
+
+  /**
+   * Same as above, but only adds the observer if its not observing
+   * the node already.
+   *
+   * For mutation observers that implement nsIAnimationObserver, use
+   * AddAnimationObserverUnlessExists instead.
+   */
+  void AddMutationObserverUnlessExists(nsIMutationObserver* aMutationObserver) {
+    nsSlots* s = Slots();
+    if (aMutationObserver &&
+        !s->mMutationObservers.contains(aMutationObserver)) {
+      s->mMutationObservers.pushBack(aMutationObserver);
+    }
+  }
+
+  void AddMutationObserverUnlessExists(
+      nsMultiMutationObserver* aMultiMutationObserver);
+  /**
+   * Same as AddMutationObserver, but for nsIAnimationObservers.  This
+   * additionally records on the document that animation observers have
+   * been registered, which is used to determine whether notifications
+   * must be fired when animations are added, removed or changed.
+   */
+  void AddAnimationObserver(nsIAnimationObserver* aAnimationObserver);
+
+  /**
+   * Same as above, but only adds the observer if its not observing
+   * the node already.
+   */
+  void AddAnimationObserverUnlessExists(
+      nsIAnimationObserver* aAnimationObserver);
+
+  /**
+   * Removes a mutation observer.
+   */
+  void RemoveMutationObserver(nsIMutationObserver* aMutationObserver) {
+    nsSlots* s = GetExistingSlots();
+    if (s) {
+      s->mMutationObservers.remove(aMutationObserver);
+    }
+  }
+
+  void RemoveMutationObserver(nsMultiMutationObserver* aMultiMutationObserver);
+
+  mozilla::SafeDoublyLinkedList<nsIMutationObserver>* GetMutationObservers();
+
+  /**
+   * Helper methods to access ancestor node(s) of type T.
+   * The implementations of the methods are in mozilla/dom/AncestorIterator.h.
+   */
+  template <typename T>
+  inline mozilla::dom::AncestorsOfTypeIterator<T> AncestorsOfType() const;
+
+  template <typename T>
+  inline mozilla::dom::InclusiveAncestorsOfTypeIterator<T>
+  InclusiveAncestorsOfType() const;
+
+  template <typename T>
+  inline mozilla::dom::FlatTreeAncestorsOfTypeIterator<T>
+  FlatTreeAncestorsOfType() const;
+
+  template <typename T>
+  inline mozilla::dom::InclusiveFlatTreeAncestorsOfTypeIterator<T>
+  InclusiveFlatTreeAncestorsOfType() const;
+
+  template <typename T>
+  T* FirstAncestorOfType() const;
+
+ private:
+  /**
+   * Walks aNode, its attributes and, if aDeep is true, its descendant nodes.
+   * If aClone is true the nodes will be cloned. If aNewNodeInfoManager is
+   * not null, it is used to create new nodeinfos for the nodes. Also reparents
+   * the XPConnect wrappers for the nodes into aReparentScope if non-null.
+   *
+   * @param aNode Node to adopt/clone.
+   * @param aClone If true the node will be cloned and the cloned node will
+   *               be returned.
+   * @param aDeep If true the function will be called recursively on
+   *              descendants of the node
+   * @param aNewNodeInfoManager The nodeinfo manager to use to create new
+   *                            nodeinfos for aNode and its attributes and
+   *                            descendants. May be null if the nodeinfos
+   *                            shouldn't be changed.
+   * @param aReparentScope Scope into which wrappers should be reparented, or
+   *                             null if no reparenting should be done.
+   * @param aParent If aClone is true the cloned node will be appended to
+   *                aParent's children. May be null. If not null then aNode
+   *                must be an nsIContent.
+   * @param aError The error, if any.
+   *
+   * @return If aClone is true then the cloned node will be returned,
+   *          unless an error occurred.  In error conditions, null
+   *          will be returned.
+   */
+  static already_AddRefed<nsINode> CloneAndAdopt(
+      nsINode* aNode, bool aClone, bool aDeep,
+      nsNodeInfoManager* aNewNodeInfoManager,
+      JS::Handle<JSObject*> aReparentScope, nsINode* aParent,
+      mozilla::ErrorResult& aError);
+
+ public:
+  /**
+   * Walks the node, its attributes and descendant nodes. If aNewNodeInfoManager
+   * is not null, it is used to create new nodeinfos for the nodes. Also
+   * reparents the XPConnect wrappers for the nodes into aReparentScope if
+   * non-null.
+   *
+   * @param aNewNodeInfoManager The nodeinfo manager to use to create new
+   *                            nodeinfos for the node and its attributes and
+   *                            descendants. May be null if the nodeinfos
+   *                            shouldn't be changed.
+   * @param aReparentScope New scope for the wrappers, or null if no reparenting
+   *                       should be done.
+   * @param aError The error, if any.
+   */
+  void Adopt(nsNodeInfoManager* aNewNodeInfoManager,
+             JS::Handle<JSObject*> aReparentScope,
+             mozilla::ErrorResult& aError);
+
+  /**
+   * Clones the node, its attributes and, if aDeep is true, its descendant nodes
+   * If aNewNodeInfoManager is not null, it is used to create new nodeinfos for
+   * the clones.
+   *
+   * @param aDeep If true the function will be called recursively on
+   *              descendants of the node
+   * @param aNewNodeInfoManager The nodeinfo manager to use to create new
+   *                            nodeinfos for the node and its attributes and
+   *                            descendants. May be null if the nodeinfos
+   *                            shouldn't be changed.
+   * @param aError The error, if any.
+   *
+   * @return The newly created node.  Null in error conditions.
+   */
+  already_AddRefed<nsINode> Clone(bool aDeep,
+                                  nsNodeInfoManager* aNewNodeInfoManager,
+                                  mozilla::ErrorResult& aError);
+
+  /**
+   * Clones this node. This needs to be overriden by all node classes. aNodeInfo
+   * should be identical to this node's nodeInfo, except for the document which
+   * may be different. When cloning an element, all attributes of the element
+   * will be cloned. The children of the node will not be cloned.
+   *
+   * @param aNodeInfo the nodeinfo to use for the clone
+   * @param aResult the clone
+   */
+  virtual nsresult Clone(mozilla::dom::NodeInfo*, nsINode** aResult) const = 0;
+
+  // This class can be extended by subclasses that wish to store more
+  // information in the slots.
+  class nsSlots {
+   public:
+    nsSlots();
+
+    // If needed we could remove the vtable pointer this dtor causes by
+    // putting a DestroySlots function on nsINode
+    virtual ~nsSlots();
+
+    virtual void Traverse(nsCycleCollectionTraversalCallback&);
+    virtual void Unlink(nsINode&);
+
+    /**
+     * A list of mutation observers
+     */
+    mozilla::SafeDoublyLinkedList<nsIMutationObserver> mMutationObservers;
+
+    /**
+     * An object implementing NodeList for this content (childNodes)
+     * @see NodeList
+     * @see nsGenericHTMLElement::GetChildNodes
+     */
+    RefPtr<nsAttrChildContentList> mChildNodes;
+
+    /**
+     * Weak reference to this node.  This is cleared by the destructor of
+     * nsNodeWeakReference.
+     */
+    nsNodeWeakReference* MOZ_NON_OWNING_REF mWeakReference;
+
+    /**
+     * A set of ranges which are in the selection and which have this node as
+     * their endpoints' closest common inclusive ancestor
+     * (https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor).  This is
+     * a UniquePtr instead of just a LinkedList, because that prevents us from
+     * pushing DOMSlots up to the next allocation bucket size, at the cost of
+     * some complexity.
+     */
+    mozilla::UniquePtr<mozilla::LinkedList<mozilla::dom::AbstractRange>>
+        mClosestCommonInclusiveAncestorRanges;
+  };
+
+  /**
+   * Functions for managing flags and slots
+   */
+#ifdef DEBUG
+  nsSlots* DebugGetSlots() { return Slots(); }
+#endif
+
+  void SetFlags(FlagsType aFlagsToSet) {
+    NS_ASSERTION(
+        !(aFlagsToSet &
+          (NODE_IS_NATIVE_ANONYMOUS_ROOT | NODE_IS_IN_NATIVE_ANONYMOUS_SUBTREE |
+           NODE_DESCENDANTS_NEED_FRAMES | NODE_NEEDS_FRAME |
+           NODE_HAS_BEEN_IN_UA_WIDGET)) ||
+            IsContent(),
+        "Flag only permitted on nsIContent nodes");
+    nsWrapperCache::SetFlags(aFlagsToSet);
+  }
+
+  void UnsetFlags(FlagsType aFlagsToUnset) {
+    NS_ASSERTION(!(aFlagsToUnset & (NODE_HAS_BEEN_IN_UA_WIDGET |
+                                    NODE_IS_NATIVE_ANONYMOUS_ROOT)),
+                 "Trying to unset write-only flags");
+    nsWrapperCache::UnsetFlags(aFlagsToUnset);
+  }
+
+  void SetEditableFlag(bool aEditable) {
+    if (aEditable) {
+      SetFlags(NODE_IS_EDITABLE);
+    } else {
+      UnsetFlags(NODE_IS_EDITABLE);
+    }
+  }
+
+  inline bool IsEditable() const;
+
+  /**
+   * Check if this node is an editing host. For avoiding confusion, this always
+   * returns false if the node is in the design mode document.
+   */
+  inline bool IsEditingHost() const;
+
+  /**
+   * Check if this node is in design mode or not.  When this returns true and:
+   * - if this is a Document node, it's the design mode root.
+   * - if this is a content node, it's connected, it's not in a shadow tree
+   *   (except shadow tree for UI widget and native anonymous subtree) and its
+   *   uncomposed document is in design mode.
+   * Note that returning true does NOT mean the node or its children is
+   * editable.  E.g., when this node is in a shadow tree of a UA widget and its
+   * host is in design mode.
+   */
+  inline bool IsInDesignMode() const;
+
+  /**
+   * Returns true if |this| or any of its ancestors is native anonymous.
+   */
+  bool IsInNativeAnonymousSubtree() const {
+    return HasFlag(NODE_IS_IN_NATIVE_ANONYMOUS_SUBTREE);
+  }
+
+  /**
+   * If |this| or any ancestor is native anonymous, return the root of the
+   * native anonymous subtree. Note that in case of nested native anonymous
+   * content, this returns the innermost root, not the outermost.
+   */
+  nsIContent* GetClosestNativeAnonymousSubtreeRoot() const {
+    if (!IsInNativeAnonymousSubtree()) {
+      MOZ_ASSERT(!HasBeenInUAWidget(), "UA widget implies anonymous");
+      return nullptr;
+    }
+    MOZ_ASSERT(IsContent(), "How did non-content end up in NAC?");
+    if (HasBeenInUAWidget()) {
+      // reinterpret_cast because in this header we don't know ShadowRoot is an
+      // nsIContent. ShadowRoot constructor asserts this is correct.
+      return reinterpret_cast<nsIContent*>(GetContainingShadow());
+    }
+    for (const nsINode* node = this; node; node = node->GetParentNode()) {
+      if (node->IsRootOfNativeAnonymousSubtree()) {
+        return const_cast<nsINode*>(node)->AsContent();
+      }
+    }
+    // FIXME(emilio): This should not happen, usually, but editor removes nodes
+    // in native anonymous subtrees, and we don't clean nodes from the current
+    // event content stack from ContentRemoved, so it can actually happen, see
+    // bug 1510208.
+    NS_WARNING("GetClosestNativeAnonymousSubtreeRoot on disconnected NAC!");
+    return nullptr;
+  }
+
+  /**
+   * If |this| or any ancestor is native anonymous, return the parent of the
+   * native anonymous subtree. Note that in case of nested native anonymous
+   * content, this returns the parent or host of the innermost root, not the
+   * outermost.
+   */
+  nsIContent* GetClosestNativeAnonymousSubtreeRootParentOrHost() const {
+    // We could put this in nsIContentInlines.h or such to avoid this
+    // reinterpret_cast, but it doesn't seem worth it.
+    const auto* root = reinterpret_cast<const nsINode*>(
+        GetClosestNativeAnonymousSubtreeRoot());
+    if (!root) {
+      return nullptr;
+    }
+    if (nsIContent* parent = root->GetParent()) {
+      return parent;
+    }
+    if (MOZ_UNLIKELY(root->IsInShadowTree())) {
+      return root->DoGetShadowHost();
+    }
+    return nullptr;
+  }
+
+  /**
+   * Gets the root of the node tree for this content if it is in a shadow tree.
+   */
+  mozilla::dom::ShadowRoot* GetContainingShadow() const;
+  /**
+   * Gets the shadow host if this content is in a shadow tree. That is, the host
+   * of |GetContainingShadow|, if its not null.
+   *
+   * @return The shadow host, if this is in shadow tree, or null.
+   */
+  mozilla::dom::Element* GetContainingShadowHost() const;
+
+  bool IsInSVGUseShadowTree() const {
+    return !!GetContainingSVGUseShadowHost();
+  }
+
+  mozilla::dom::SVGUseElement* GetContainingSVGUseShadowHost() const {
+    if (!IsInShadowTree()) {
+      return nullptr;
+    }
+    return DoGetContainingSVGUseShadowHost();
+  }
+
+  // Whether this node has ever been part of a UA widget shadow tree.
+  bool HasBeenInUAWidget() const { return HasFlag(NODE_HAS_BEEN_IN_UA_WIDGET); }
+
+  // True for native anonymous content and for content in UA widgets.
+  // Only nsIContent can fulfill this condition.
+  bool ChromeOnlyAccess() const { return IsInNativeAnonymousSubtree(); }
+
+  const nsIContent* GetChromeOnlyAccessSubtreeRootParent() const {
+    return GetClosestNativeAnonymousSubtreeRootParentOrHost();
+  }
+
+  bool IsInShadowTree() const { return HasFlag(NODE_IS_IN_SHADOW_TREE); }
+
+  /**
+   * Get whether this node is C++-generated anonymous content
+   * @see nsIAnonymousContentCreator
+   * @return whether this content is anonymous
+   */
+  bool IsRootOfNativeAnonymousSubtree() const {
+    NS_ASSERTION(
+        !HasFlag(NODE_IS_NATIVE_ANONYMOUS_ROOT) || IsInNativeAnonymousSubtree(),
+        "Some flags seem to be missing!");
+    return HasFlag(NODE_IS_NATIVE_ANONYMOUS_ROOT);
+  }
+
+  // Whether this node is the root of a ChromeOnlyAccess DOM subtree.
+  bool IsRootOfChromeAccessOnlySubtree() const {
+    return IsRootOfNativeAnonymousSubtree();
+  }
+
+  /** Whether this is the container of a ::before pseudo-element. */
+  bool IsGeneratedContentContainerForBefore() const {
+    return IsRootOfNativeAnonymousSubtree() &&
+           mNodeInfo->NameAtom() == nsGkAtoms::mozgeneratedcontentbefore;
+  }
+
+  /** Whether this is the container of an ::after pseudo-element. */
+  bool IsGeneratedContentContainerForAfter() const {
+    return IsRootOfNativeAnonymousSubtree() &&
+           mNodeInfo->NameAtom() == nsGkAtoms::mozgeneratedcontentafter;
+  }
+
+  /** Whether this is the container of a ::marker pseudo-element. */
+  bool IsGeneratedContentContainerForMarker() const {
+    return IsRootOfNativeAnonymousSubtree() &&
+           mNodeInfo->NameAtom() == nsGkAtoms::mozgeneratedcontentmarker;
+  }
+
+  /**
+   * Returns true if |this| node is the closest common inclusive ancestor
+   * (https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor) of the
+   * start/end nodes of a Range in a Selection or a descendant of such a common
+   * ancestor. This node is definitely not selected when |false| is returned,
+   * but it may or may not be selected when |true| is returned.
+   */
+  bool IsMaybeSelected() const {
+    return IsDescendantOfClosestCommonInclusiveAncestorForRangeInSelection() ||
+           IsClosestCommonInclusiveAncestorForRangeInSelection();
+  }
+
+  /**
+   * Return true if any part of (this, aStartOffset) .. (this, aEndOffset)
+   * overlaps any nsRange in
+   * GetClosestCommonInclusiveAncestorForRangeInSelection ranges (i.e.
+   * where this is a descendant of a range's common inclusive ancestor node).
+   * If a nsRange starts in (this, aEndOffset) or if it ends in
+   * (this, aStartOffset) then it is non-overlapping and the result is false
+   * for that nsRange.  Collapsed ranges always counts as non-overlapping.
+   *
+   * @param aStartOffset has to be less or equal to aEndOffset.
+   */
+  bool IsSelected(uint32_t aStartOffset, uint32_t aEndOffset) const;
+
+  /**
+   * Get the root element of the text editor associated with this node or the
+   * root element of the text editor of the ancestor 'TextControlElement' if
+   * this is in its native anonymous subtree.  I.e., this returns anonymous
+   * `<div>` element of a `TextEditor`. Note that this can be used only for
+   * getting root content of `<input>` or `<textarea>`.  I.e., this method
+   * doesn't support HTML editors. Note that this may create a `TextEditor`
+   * instance, and it means that the `TextEditor` may modify its native
+   * anonymous subtree and may run selection listeners.
+   */
+  MOZ_CAN_RUN_SCRIPT mozilla::dom::Element* GetAnonymousRootElementOfTextEditor(
+      mozilla::TextEditor** aTextEditor = nullptr);
+
+  /**
+   * Get the nearest selection root, ie. the node that will be selected if the
+   * user does "Select All" while the focus is in this node. Note that if this
+   * node is not in an editor, the result comes from the nsFrameSelection that
+   * is related to aPresShell, so the result might not be the ancestor of this
+   * node. Be aware that if this node and the computed selection limiter are
+   * not in same subtree, this returns the root content of the closeset subtree.
+   */
+  MOZ_CAN_RUN_SCRIPT nsIContent* GetSelectionRootContent(
+      mozilla::PresShell* aPresShell);
+
+  nsINodeList* ChildNodes();
+
+  nsIContent* GetFirstChild() const { return mFirstChild; }
+
+  nsIContent* GetLastChild() const;
+
+  /**
+   * Implementation is in Document.h, because it needs to cast from
+   * Document* to nsINode*.
+   */
+  Document* GetOwnerDocument() const;
+
+  // TODO: Convert this to MOZ_CAN_RUN_SCRIPT (bug 1415230)
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY void Normalize();
+
+  /**
+   * Get the base URI for any relative URIs within this piece of
+   * content. Generally, this is the document's base URI, but certain
+   * content carries a local base for backward compatibility.
+   *
+   * @return the base URI.  May return null.
+   */
+  virtual nsIURI* GetBaseURI(bool aTryUseXHRDocBaseURI = false) const = 0;
+  nsIURI* GetBaseURIObject() const;
+
+  /**
+   * Return true if the node may be apz aware. There are two cases. One is that
+   * the node is apz aware (such as HTMLInputElement with number type). The
+   * other is that the node has apz aware listeners. This is a non-virtual
+   * function which calls IsNodeApzAwareInternal only when the MayBeApzAware is
+   * set. We check the details in IsNodeApzAwareInternal which may be overriden
+   * by child classes
+   */
+  bool IsNodeApzAware() const {
+    return NodeMayBeApzAware() ? IsNodeApzAwareInternal() : false;
+  }
+
+  /**
+   * Override this function and set the flag MayBeApzAware in case the node has
+   * to let APZC be aware of it. It's used when the node may handle the apz
+   * aware events and may do preventDefault to stop APZC to do default actions.
+   *
+   * For example, instead of scrolling page by APZ, we handle mouse wheel event
+   * in HTMLInputElement with number type as increasing / decreasing its value.
+   */
+  virtual bool IsNodeApzAwareInternal() const;
+
+  void GetTextContent(nsAString& aTextContent, mozilla::OOMReporter& aError) {
+    GetTextContentInternal(aTextContent, aError);
+  }
+  void SetTextContent(const nsAString& aTextContent,
+                      nsIPrincipal* aSubjectPrincipal,
+                      mozilla::ErrorResult& aError) {
+    SetTextContentInternal(aTextContent, aSubjectPrincipal, aError);
+  }
+  void SetTextContent(const nsAString& aTextContent,
+                      mozilla::ErrorResult& aError) {
+    SetTextContentInternal(aTextContent, nullptr, aError);
+  }
+
+  mozilla::dom::Element* QuerySelector(const nsACString& aSelector,
+                                       mozilla::ErrorResult& aResult);
+  already_AddRefed<nsINodeList> QuerySelectorAll(const nsACString& aSelector,
+                                                 mozilla::ErrorResult& aResult);
+
+ protected:
+  // Document and ShadowRoot override this with its own (faster) version.
+  // This should really only be called for elements and document fragments.
+  mozilla::dom::Element* GetElementById(const nsAString& aId);
+
+  void AppendChildToChildList(nsIContent* aKid);
+  void InsertChildToChildList(nsIContent* aKid, nsIContent* aNextSibling);
+  void DisconnectChild(nsIContent* aKid);
+
+ public:
+  void LookupPrefix(const nsAString& aNamespace, nsAString& aResult);
+  bool IsDefaultNamespace(const nsAString& aNamespaceURI) {
+    nsAutoString defaultNamespace;
+    LookupNamespaceURI(u""_ns, defaultNamespace);
+    return aNamespaceURI.Equals(defaultNamespace);
+  }
+  void LookupNamespaceURI(const nsAString& aNamespacePrefix,
+                          nsAString& aNamespaceURI);
+
+  nsIContent* GetNextSibling() const { return mNextSibling; }
+  nsIContent* GetPreviousSibling() const;
+
+  /**
+   * Return true if the node is being removed from the parent, it means that
+   * the node still knows the container which it's disconnected from, but the
+   * node has already been removed from the child node chain of the container.
+   * I.e., Return true between a call of DisconnectChild of the parent and
+   * a call of UnbindFromTree of the node.
+   */
+  bool IsBeingRemoved() const {
+    return mParent && !mNextSibling && !mPreviousOrLastSibling;
+  }
+
+  /**
+   * Get the next node in the pre-order tree traversal of the DOM.  If
+   * aRoot is non-null, then it must be an ancestor of |this|
+   * (possibly equal to |this|) and only nodes that are descendants of
+   * aRoot, not including aRoot itself, will be returned.  Returns
+   * null if there are no more nodes to traverse.
+   */
+  nsIContent* GetNextNode(const nsINode* aRoot = nullptr) const {
+    return GetNextNodeImpl(aRoot, false);
+  }
+
+  /**
+   * Get the next node in the pre-order tree traversal of the DOM but ignoring
+   * the children of this node.  If aRoot is non-null, then it must be an
+   * ancestor of |this| (possibly equal to |this|) and only nodes that are
+   * descendants of aRoot, not including aRoot itself, will be returned.
+   * Returns null if there are no more nodes to traverse.
+   */
+  nsIContent* GetNextNonChildNode(const nsINode* aRoot = nullptr) const {
+    return GetNextNodeImpl(aRoot, true);
+  }
+
+  /**
+   * Returns true if 'this' is either document or element or
+   * document fragment and aOther is a descendant in the same
+   * anonymous tree.
+   */
+  bool Contains(const nsINode* aOther) const;
+
+  bool UnoptimizableCCNode() const;
+
+  /**
+   * Fire a DOMNodeRemoved mutation event for all children of this node
+   * TODO: Convert this to MOZ_CAN_RUN_SCRIPT (bug 1415230)
+   */
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY void FireNodeRemovedForChildren();
+
+  void QueueDevtoolsAnonymousEvent(bool aIsRemove);
+
+ private:
+  mozilla::dom::SVGUseElement* DoGetContainingSVGUseShadowHost() const;
+
+  nsIContent* GetNextNodeImpl(const nsINode* aRoot,
+                              const bool aSkipChildren) const {
+#ifdef DEBUG
+    if (aRoot) {
+      // TODO: perhaps nsINode::IsInclusiveDescendantOf could be used instead.
+      const nsINode* cur = this;
+      for (; cur; cur = cur->GetParentNode())
+        if (cur == aRoot) break;
+      NS_ASSERTION(cur, "aRoot not an ancestor of |this|?");
+    }
+#endif
+    if (!aSkipChildren) {
+      nsIContent* kid = GetFirstChild();
+      if (kid) {
+        return kid;
+      }
+    }
+    if (this == aRoot) {
+      return nullptr;
+    }
+    const nsINode* cur = this;
+    while (1) {
+      nsIContent* next = cur->GetNextSibling();
+      if (next) {
+        return next;
+      }
+      nsINode* parent = cur->GetParentNode();
+      if (parent == aRoot) {
+        return nullptr;
+      }
+      cur = parent;
+    }
+    MOZ_ASSERT_UNREACHABLE("How did we get here?");
+  }
+
+ public:
+  /**
+   * Get the previous nsIContent in the pre-order tree traversal of the DOM.  If
+   * aRoot is non-null, then it must be an ancestor of |this|
+   * (possibly equal to |this|) and only nsIContents that are descendants of
+   * aRoot, including aRoot itself, will be returned.  Returns
+   * null if there are no more nsIContents to traverse.
+   */
+  nsIContent* GetPrevNode(const nsINode* aRoot = nullptr) const {
+#ifdef DEBUG
+    if (aRoot) {
+      // TODO: perhaps nsINode::IsInclusiveDescendantOf could be used instead.
+      const nsINode* cur = this;
+      for (; cur; cur = cur->GetParentNode())
+        if (cur == aRoot) break;
+      NS_ASSERTION(cur, "aRoot not an ancestor of |this|?");
+    }
+#endif
+
+    if (this == aRoot) {
+      return nullptr;
+    }
+    nsIContent* cur = this->GetParent();
+    nsIContent* iter = this->GetPreviousSibling();
+    while (iter) {
+      cur = iter;
+      iter = reinterpret_cast<nsINode*>(iter)->GetLastChild();
+    }
+    return cur;
+  }
+
+  /**
+   * Boolean flags
+   */
+ private:
+  enum BooleanFlag {
+    // Set if we're being used from -moz-element
+    NodeHasRenderingObservers,
+    // Set if our parent chain (including this node itself) terminates
+    // in a document
+    IsInDocument,
+    // Set if we're part of the composed doc.
+    // https://dom.spec.whatwg.org/#connected
+    IsConnected,
+    // Set if mParent is an nsIContent
+    ParentIsContent,
+    // Set if this node is an Element
+    NodeIsElement,
+    // Set if the element has a non-empty id attribute. This can in rare
+    // cases lie for nsXMLElement, such as when the node has been moved between
+    // documents with different id mappings.
+    ElementHasID,
+    // Set if the element might have a class.
+    ElementMayHaveClass,
+    // Set if the element might have inline style.
+    ElementMayHaveStyle,
+    // Set if the element has a name attribute set.
+    ElementHasName,
+    // Set if the element has a part attribute set.
+    ElementHasPart,
+    // Set if the element might have a contenteditable attribute set.
+    ElementMayHaveContentEditableAttr,
+    // Set if the node is the closest common inclusive ancestor of the start/end
+    // nodes of a Range that is in a Selection.
+    NodeIsClosestCommonInclusiveAncestorForRangeInSelection,
+    // Set if the node is a descendant of a node with the above bit set.
+    NodeIsDescendantOfClosestCommonInclusiveAncestorForRangeInSelection,
+    // Set if CanSkipInCC check has been done for this subtree root.
+    NodeIsCCMarkedRoot,
+    // Maybe set if this node is in black subtree.
+    NodeIsCCBlackTree,
+    // Maybe set if the node is a root of a subtree
+    // which needs to be kept in the purple buffer.
+    NodeIsPurpleRoot,
+    // Set if the element has some style states locked
+    ElementHasLockedStyleStates,
+    // Set if element has pointer locked
+    ElementHasPointerLock,
+    // Set if the node may have DOMMutationObserver attached to it.
+    NodeMayHaveDOMMutationObserver,
+    // Set if node is Content
+    NodeIsContent,
+    // Set if the node has animations or transitions
+    ElementHasAnimations,
+    // Set if node has a dir attribute with a valid value (ltr, rtl, or auto).
+    // Note that we cannot compute this from the dir attribute event state
+    // flags, because we can't use those to distinguish
+    // <bdi dir="some-invalid-value"> and <bdi dir="auto">.
+    NodeHasValidDirAttribute,
+    // Set if the node has dir=auto and has a property pointing to the text
+    // node that determines its direction
+    NodeHasDirAutoSet,
+    // Set if the node is a text node descendant of a node with dir=auto
+    // and has a TextNodeDirectionalityMap property listing the elements whose
+    // direction it determines.
+    NodeHasTextNodeDirectionalityMap,
+    // Set if a node in the node's parent chain has dir=auto.
+    NodeAncestorHasDirAuto,
+    // Set if the node is handling a click.
+    NodeHandlingClick,
+    // Set if the element has a parser insertion mode other than "in body",
+    // per the HTML5 "Parse state" section.
+    ElementHasWeirdParserInsertionMode,
+    // Parser sets this flag if it has notified about the node.
+    ParserHasNotified,
+    // Sets if the node is apz aware or we have apz aware listeners.
+    MayBeApzAware,
+    // Set if the element might have any kind of anonymous content children,
+    // which would not be found through the element's children list.
+    ElementMayHaveAnonymousChildren,
+    // Set if element has CustomElementData.
+    ElementHasCustomElementData,
+    // Set if the element was created from prototype cache and
+    // its l10n attributes haven't been changed.
+    ElementCreatedFromPrototypeAndHasUnmodifiedL10n,
+    // Guard value
+    BooleanFlagCount
+  };
+
+  void SetBoolFlag(BooleanFlag name, bool value) {
+    static_assert(BooleanFlagCount <= 8 * sizeof(mBoolFlags),
+                  "Too many boolean flags");
+    mBoolFlags = (mBoolFlags & ~(1 << name)) | (value << name);
+  }
+
+  void SetBoolFlag(BooleanFlag name) {
+    static_assert(BooleanFlagCount <= 8 * sizeof(mBoolFlags),
+                  "Too many boolean flags");
+    mBoolFlags |= (1 << name);
+  }
+
+  void ClearBoolFlag(BooleanFlag name) {
+    static_assert(BooleanFlagCount <= 8 * sizeof(mBoolFlags),
+                  "Too many boolean flags");
+    mBoolFlags &= ~(1 << name);
+  }
+
+  bool GetBoolFlag(BooleanFlag name) const {
+    static_assert(BooleanFlagCount <= 8 * sizeof(mBoolFlags),
+                  "Too many boolean flags");
+    return mBoolFlags & (1 << name);
+  }
+
+ public:
+  bool HasRenderingObservers() const {
+    return GetBoolFlag(NodeHasRenderingObservers);
+  }
+  void SetHasRenderingObservers(bool aValue) {
+    SetBoolFlag(NodeHasRenderingObservers, aValue);
+  }
+  bool IsContent() const { return GetBoolFlag(NodeIsContent); }
+  bool HasID() const { return GetBoolFlag(ElementHasID); }
+  bool MayHaveClass() const { return GetBoolFlag(ElementMayHaveClass); }
+  void SetMayHaveClass() { SetBoolFlag(ElementMayHaveClass); }
+  bool MayHaveStyle() const { return GetBoolFlag(ElementMayHaveStyle); }
+  bool HasName() const { return GetBoolFlag(ElementHasName); }
+  bool HasPartAttribute() const { return GetBoolFlag(ElementHasPart); }
+  bool MayHaveContentEditableAttr() const {
+    return GetBoolFlag(ElementMayHaveContentEditableAttr);
+  }
+  /**
+   * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor
+   */
+  bool IsClosestCommonInclusiveAncestorForRangeInSelection() const {
+    return GetBoolFlag(NodeIsClosestCommonInclusiveAncestorForRangeInSelection);
+  }
+  /**
+   * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor
+   */
+  void SetClosestCommonInclusiveAncestorForRangeInSelection() {
+    SetBoolFlag(NodeIsClosestCommonInclusiveAncestorForRangeInSelection);
+  }
+  /**
+   * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor
+   */
+  void ClearClosestCommonInclusiveAncestorForRangeInSelection() {
+    ClearBoolFlag(NodeIsClosestCommonInclusiveAncestorForRangeInSelection);
+  }
+  /**
+   * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor
+   */
+  bool IsDescendantOfClosestCommonInclusiveAncestorForRangeInSelection() const {
+    return GetBoolFlag(
+        NodeIsDescendantOfClosestCommonInclusiveAncestorForRangeInSelection);
+  }
+  /**
+   * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor
+   */
+  void SetDescendantOfClosestCommonInclusiveAncestorForRangeInSelection() {
+    SetBoolFlag(
+        NodeIsDescendantOfClosestCommonInclusiveAncestorForRangeInSelection);
+  }
+  /**
+   * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor
+   */
+  void ClearDescendantOfClosestCommonInclusiveAncestorForRangeInSelection() {
+    ClearBoolFlag(
+        NodeIsDescendantOfClosestCommonInclusiveAncestorForRangeInSelection);
+  }
+
+  void SetCCMarkedRoot(bool aValue) { SetBoolFlag(NodeIsCCMarkedRoot, aValue); }
+  bool CCMarkedRoot() const { return GetBoolFlag(NodeIsCCMarkedRoot); }
+  void SetInCCBlackTree(bool aValue) { SetBoolFlag(NodeIsCCBlackTree, aValue); }
+  bool InCCBlackTree() const { return GetBoolFlag(NodeIsCCBlackTree); }
+  void SetIsPurpleRoot(bool aValue) { SetBoolFlag(NodeIsPurpleRoot, aValue); }
+  bool IsPurpleRoot() const { return GetBoolFlag(NodeIsPurpleRoot); }
+  bool MayHaveDOMMutationObserver() {
+    return GetBoolFlag(NodeMayHaveDOMMutationObserver);
+  }
+  void SetMayHaveDOMMutationObserver() {
+    SetBoolFlag(NodeMayHaveDOMMutationObserver, true);
+  }
+  bool HasListenerManager() { return HasFlag(NODE_HAS_LISTENERMANAGER); }
+  bool HasPointerLock() const { return GetBoolFlag(ElementHasPointerLock); }
+  void SetPointerLock() { SetBoolFlag(ElementHasPointerLock); }
+  void ClearPointerLock() { ClearBoolFlag(ElementHasPointerLock); }
+  bool MayHaveAnimations() const { return GetBoolFlag(ElementHasAnimations); }
+  void SetMayHaveAnimations() { SetBoolFlag(ElementHasAnimations); }
+  void ClearMayHaveAnimations() { ClearBoolFlag(ElementHasAnimations); }
+  void SetHasValidDir() { SetBoolFlag(NodeHasValidDirAttribute); }
+  void ClearHasValidDir() { ClearBoolFlag(NodeHasValidDirAttribute); }
+  bool HasValidDir() const { return GetBoolFlag(NodeHasValidDirAttribute); }
+  void SetHasDirAutoSet() {
+    MOZ_ASSERT(NodeType() != TEXT_NODE, "SetHasDirAutoSet on text node");
+    SetBoolFlag(NodeHasDirAutoSet);
+  }
+  void ClearHasDirAutoSet() {
+    MOZ_ASSERT(NodeType() != TEXT_NODE, "ClearHasDirAutoSet on text node");
+    ClearBoolFlag(NodeHasDirAutoSet);
+  }
+  bool HasDirAutoSet() const { return GetBoolFlag(NodeHasDirAutoSet); }
+  void SetHasTextNodeDirectionalityMap() {
+    MOZ_ASSERT(NodeType() == TEXT_NODE,
+               "SetHasTextNodeDirectionalityMap on non-text node");
+    SetBoolFlag(NodeHasTextNodeDirectionalityMap);
+  }
+  void ClearHasTextNodeDirectionalityMap() {
+    MOZ_ASSERT(NodeType() == TEXT_NODE,
+               "ClearHasTextNodeDirectionalityMap on non-text node");
+    ClearBoolFlag(NodeHasTextNodeDirectionalityMap);
+  }
+  bool HasTextNodeDirectionalityMap() const {
+    MOZ_ASSERT(NodeType() == TEXT_NODE,
+               "HasTextNodeDirectionalityMap on non-text node");
+    return GetBoolFlag(NodeHasTextNodeDirectionalityMap);
+  }
+
+  void SetAncestorHasDirAuto() { SetBoolFlag(NodeAncestorHasDirAuto); }
+  void ClearAncestorHasDirAuto() { ClearBoolFlag(NodeAncestorHasDirAuto); }
+  bool AncestorHasDirAuto() const {
+    return GetBoolFlag(NodeAncestorHasDirAuto);
+  }
+
+  // Implemented in nsIContentInlines.h.
+  inline bool NodeOrAncestorHasDirAuto() const;
+
+  void SetParserHasNotified() { SetBoolFlag(ParserHasNotified); };
+  bool HasParserNotified() { return GetBoolFlag(ParserHasNotified); }
+
+  void SetMayBeApzAware() { SetBoolFlag(MayBeApzAware); }
+  bool NodeMayBeApzAware() const { return GetBoolFlag(MayBeApzAware); }
+
+  void SetMayHaveAnonymousChildren() {
+    SetBoolFlag(ElementMayHaveAnonymousChildren);
+  }
+  bool MayHaveAnonymousChildren() const {
+    return GetBoolFlag(ElementMayHaveAnonymousChildren);
+  }
+
+  void SetHasCustomElementData() { SetBoolFlag(ElementHasCustomElementData); }
+  bool HasCustomElementData() const {
+    return GetBoolFlag(ElementHasCustomElementData);
+  }
+
+  void SetElementCreatedFromPrototypeAndHasUnmodifiedL10n() {
+    SetBoolFlag(ElementCreatedFromPrototypeAndHasUnmodifiedL10n);
+  }
+  bool HasElementCreatedFromPrototypeAndHasUnmodifiedL10n() {
+    return GetBoolFlag(ElementCreatedFromPrototypeAndHasUnmodifiedL10n);
+  }
+  void ClearElementCreatedFromPrototypeAndHasUnmodifiedL10n() {
+    ClearBoolFlag(ElementCreatedFromPrototypeAndHasUnmodifiedL10n);
+  }
+
+ protected:
+  void SetParentIsContent(bool aValue) { SetBoolFlag(ParentIsContent, aValue); }
+  void SetIsInDocument() { SetBoolFlag(IsInDocument); }
+  void ClearInDocument() { ClearBoolFlag(IsInDocument); }
+  void SetIsConnected(bool aConnected) { SetBoolFlag(IsConnected, aConnected); }
+  void SetNodeIsContent() { SetBoolFlag(NodeIsContent); }
+  void SetIsElement() { SetBoolFlag(NodeIsElement); }
+  void SetHasID() { SetBoolFlag(ElementHasID); }
+  void ClearHasID() { ClearBoolFlag(ElementHasID); }
+  void SetMayHaveStyle() { SetBoolFlag(ElementMayHaveStyle); }
+  void SetHasName() { SetBoolFlag(ElementHasName); }
+  void ClearHasName() { ClearBoolFlag(ElementHasName); }
+  void SetHasPartAttribute(bool aPart) { SetBoolFlag(ElementHasPart, aPart); }
+  void SetMayHaveContentEditableAttr() {
+    SetBoolFlag(ElementMayHaveContentEditableAttr);
+  }
+  void SetHasLockedStyleStates() { SetBoolFlag(ElementHasLockedStyleStates); }
+  void ClearHasLockedStyleStates() {
+    ClearBoolFlag(ElementHasLockedStyleStates);
+  }
+  bool HasLockedStyleStates() const {
+    return GetBoolFlag(ElementHasLockedStyleStates);
+  }
+  void SetHasWeirdParserInsertionMode() {
+    SetBoolFlag(ElementHasWeirdParserInsertionMode);
+  }
+  bool HasWeirdParserInsertionMode() const {
+    return GetBoolFlag(ElementHasWeirdParserInsertionMode);
+  }
+  bool HandlingClick() const { return GetBoolFlag(NodeHandlingClick); }
+  void SetHandlingClick() { SetBoolFlag(NodeHandlingClick); }
+  void ClearHandlingClick() { ClearBoolFlag(NodeHandlingClick); }
+
+  void SetSubtreeRootPointer(nsINode* aSubtreeRoot) {
+    NS_ASSERTION(aSubtreeRoot, "aSubtreeRoot can never be null!");
+    NS_ASSERTION(!(IsContent() && IsInUncomposedDoc()) && !IsInShadowTree(),
+                 "Shouldn't be here!");
+    mSubtreeRoot = aSubtreeRoot;
+  }
+
+  void ClearSubtreeRootPointer() { mSubtreeRoot = nullptr; }
+
+ public:
+  // Makes nsINode object to keep aObject alive.
+  void BindObject(nsISupports* aObject);
+  // After calling UnbindObject nsINode object doesn't keep
+  // aObject alive anymore.
+  void UnbindObject(nsISupports* aObject);
+
+  void GenerateXPath(nsAString& aResult);
+
+  already_AddRefed<mozilla::dom::AccessibleNode> GetAccessibleNode();
+
+  /**
+   * Returns the length of this node, as specified at
+   * <http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-node-length>
+   */
+  uint32_t Length() const;
+
+  void GetNodeName(mozilla::dom::DOMString& aNodeName) {
+    const nsString& nodeName = NodeName();
+    aNodeName.SetKnownLiveString(nodeName);
+  }
+  [[nodiscard]] nsresult GetBaseURI(nsAString& aBaseURI) const;
+  // Return the base URI for the document.
+  // The returned value may differ if the document is loaded via XHR, and
+  // when accessed from chrome privileged script and
+  // from content privileged script for compatibility.
+  void GetBaseURIFromJS(nsAString& aBaseURI, CallerType aCallerType,
+                        ErrorResult& aRv) const;
+  bool HasChildNodes() const { return HasChildren(); }
+
+  // See nsContentUtils::PositionIsBefore for aThisIndex and aOtherIndex usage.
+  uint16_t CompareDocumentPosition(
+      nsINode& aOther, mozilla::Maybe<uint32_t>* aThisIndex = nullptr,
+      mozilla::Maybe<uint32_t>* aOtherIndex = nullptr) const;
+  void GetNodeValue(nsAString& aNodeValue) { GetNodeValueInternal(aNodeValue); }
+  void SetNodeValue(const nsAString& aNodeValue, mozilla::ErrorResult& aError) {
+    SetNodeValueInternal(aNodeValue, aError);
+  }
+  virtual void GetNodeValueInternal(nsAString& aNodeValue);
+  virtual void SetNodeValueInternal(const nsAString& aNodeValue,
+                                    mozilla::ErrorResult& aError) {
+    // The DOM spec says that when nodeValue is defined to be null "setting it
+    // has no effect", so we don't throw an exception.
+  }
+  void EnsurePreInsertionValidity(nsINode& aNewChild, nsINode* aRefChild,
+                                  mozilla::ErrorResult& aError);
+  nsINode* InsertBefore(nsINode& aNode, nsINode* aChild,
+                        mozilla::ErrorResult& aError) {
+    return ReplaceOrInsertBefore(false, &aNode, aChild, aError);
+  }
+
+  /**
+   * See <https://dom.spec.whatwg.org/#dom-node-appendchild>.
+   */
+  nsINode* AppendChild(nsINode& aNode, mozilla::ErrorResult& aError) {
+    return InsertBefore(aNode, nullptr, aError);
+  }
+
+  nsINode* ReplaceChild(nsINode& aNode, nsINode& aChild,
+                        mozilla::ErrorResult& aError) {
+    return ReplaceOrInsertBefore(true, &aNode, &aChild, aError);
+  }
+  // TODO: Convert this to MOZ_CAN_RUN_SCRIPT (bug 1415230)
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY nsINode* RemoveChild(
+      nsINode& aChild, mozilla::ErrorResult& aError);
+  already_AddRefed<nsINode> CloneNode(bool aDeep, mozilla::ErrorResult& aError);
+  bool IsSameNode(nsINode* aNode);
+  bool IsEqualNode(nsINode* aNode);
+  void GetNamespaceURI(nsAString& aNamespaceURI) const {
+    mNodeInfo->GetNamespaceURI(aNamespaceURI);
+  }
+#ifdef MOZILLA_INTERNAL_API
+  void GetPrefix(nsAString& aPrefix) { mNodeInfo->GetPrefix(aPrefix); }
+#endif
+  void GetLocalName(mozilla::dom::DOMString& aLocalName) const {
+    const nsString& localName = LocalName();
+    aLocalName.SetKnownLiveString(localName);
+  }
+
+  nsDOMAttributeMap* GetAttributes();
+
+  // Helper method to remove this node from its parent. This is not exposed
+  // through WebIDL.
+  // Only call this if the node has a parent node.
+  nsresult RemoveFromParent() {
+    nsINode* parent = GetParentNode();
+    mozilla::ErrorResult rv;
+    parent->RemoveChild(*this, rv);
+    return rv.StealNSResult();
+  }
+
+  // ChildNode methods
+  inline mozilla::dom::Element* GetPreviousElementSibling() const;
+  inline mozilla::dom::Element* GetNextElementSibling() const;
+
+  MOZ_CAN_RUN_SCRIPT void Before(const Sequence<OwningNodeOrString>& aNodes,
+                                 ErrorResult& aRv);
+  MOZ_CAN_RUN_SCRIPT void After(const Sequence<OwningNodeOrString>& aNodes,
+                                ErrorResult& aRv);
+  MOZ_CAN_RUN_SCRIPT void ReplaceWith(
+      const Sequence<OwningNodeOrString>& aNodes, ErrorResult& aRv);
+  /**
+   * Remove this node from its parent, if any.
+   */
+  void Remove();
+
+  // ParentNode methods
+  mozilla::dom::Element* GetFirstElementChild() const;
+  mozilla::dom::Element* GetLastElementChild() const;
+
+  already_AddRefed<nsIHTMLCollection> GetElementsByAttribute(
+      const nsAString& aAttribute, const nsAString& aValue);
+  already_AddRefed<nsIHTMLCollection> GetElementsByAttributeNS(
+      const nsAString& aNamespaceURI, const nsAString& aAttribute,
+      const nsAString& aValue, ErrorResult& aRv);
+
+  MOZ_CAN_RUN_SCRIPT void Prepend(const Sequence<OwningNodeOrString>& aNodes,
+                                  ErrorResult& aRv);
+  MOZ_CAN_RUN_SCRIPT void Append(const Sequence<OwningNodeOrString>& aNodes,
+                                 ErrorResult& aRv);
+  MOZ_CAN_RUN_SCRIPT void ReplaceChildren(
+      const Sequence<OwningNodeOrString>& aNodes, ErrorResult& aRv);
+  MOZ_CAN_RUN_SCRIPT void ReplaceChildren(nsINode* aNode, ErrorResult& aRv);
+
+  void GetBoxQuads(const BoxQuadOptions& aOptions,
+                   nsTArray<RefPtr<DOMQuad>>& aResult, CallerType aCallerType,
+                   ErrorResult& aRv);
+
+  void GetBoxQuadsFromWindowOrigin(const BoxQuadOptions& aOptions,
+                                   nsTArray<RefPtr<DOMQuad>>& aResult,
+                                   ErrorResult& aRv);
+
+  already_AddRefed<DOMQuad> ConvertQuadFromNode(
+      DOMQuad& aQuad, const TextOrElementOrDocument& aFrom,
+      const ConvertCoordinateOptions& aOptions, CallerType aCallerType,
+      ErrorResult& aRv);
+  already_AddRefed<DOMQuad> ConvertRectFromNode(
+      DOMRectReadOnly& aRect, const TextOrElementOrDocument& aFrom,
+      const ConvertCoordinateOptions& aOptions, CallerType aCallerType,
+      ErrorResult& aRv);
+  already_AddRefed<DOMPoint> ConvertPointFromNode(
+      const DOMPointInit& aPoint, const TextOrElementOrDocument& aFrom,
+      const ConvertCoordinateOptions& aOptions, CallerType aCallerType,
+      ErrorResult& aRv);
+
+  /**
+   * See nsSlots::mClosestCommonInclusiveAncestorRanges.
+   */
+  const mozilla::LinkedList<mozilla::dom::AbstractRange>*
+  GetExistingClosestCommonInclusiveAncestorRanges() const {
+    if (!HasSlots()) {
+      return nullptr;
+    }
+    return GetExistingSlots()->mClosestCommonInclusiveAncestorRanges.get();
+  }
+
+  /**
+   * See nsSlots::mClosestCommonInclusiveAncestorRanges.
+   */
+  mozilla::LinkedList<mozilla::dom::AbstractRange>*
+  GetExistingClosestCommonInclusiveAncestorRanges() {
+    if (!HasSlots()) {
+      return nullptr;
+    }
+    return GetExistingSlots()->mClosestCommonInclusiveAncestorRanges.get();
+  }
+
+  /**
+   * See nsSlots::mClosestCommonInclusiveAncestorRanges.
+   */
+  mozilla::UniquePtr<mozilla::LinkedList<mozilla::dom::AbstractRange>>&
+  GetClosestCommonInclusiveAncestorRangesPtr() {
+    return Slots()->mClosestCommonInclusiveAncestorRanges;
+  }
+
+  nsIWeakReference* GetExistingWeakReference() {
+    return HasSlots() ? GetExistingSlots()->mWeakReference : nullptr;
+  }
+
+ protected:
+  // Override this function to create a custom slots class.
+  // Must not return null.
+  virtual nsINode::nsSlots* CreateSlots();
+
+  bool HasSlots() const { return mSlots != nullptr; }
+
+  nsSlots* GetExistingSlots() const { return mSlots; }
+
+  nsSlots* Slots() {
+    if (!HasSlots()) {
+      mSlots = CreateSlots();
+      MOZ_ASSERT(mSlots);
+    }
+    return GetExistingSlots();
+  }
+
+  /**
+   * Invalidate cached child array inside mChildNodes
+   * of type nsParentNodeChildContentList.
+   */
+  void InvalidateChildNodes();
+
+  virtual void GetTextContentInternal(nsAString& aTextContent,
+                                      mozilla::OOMReporter& aError);
+  virtual void SetTextContentInternal(const nsAString& aTextContent,
+                                      nsIPrincipal* aSubjectPrincipal,
+                                      mozilla::ErrorResult& aError) {}
+
+  void EnsurePreInsertionValidity1(mozilla::ErrorResult& aError);
+  void EnsurePreInsertionValidity2(bool aReplace, nsINode& aNewChild,
+                                   nsINode* aRefChild,
+                                   mozilla::ErrorResult& aError);
+  // TODO: Convert this to MOZ_CAN_RUN_SCRIPT (bug 1415230)
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY nsINode* ReplaceOrInsertBefore(
+      bool aReplace, nsINode* aNewChild, nsINode* aRefChild,
+      mozilla::ErrorResult& aError);
+
+  /**
+   * Returns the Element that should be used for resolving namespaces
+   * on this node (ie the ownerElement for attributes, the documentElement for
+   * documents, the node itself for elements and for other nodes the parentNode
+   * if it is an element).
+   */
+  virtual mozilla::dom::Element* GetNameSpaceElement() = 0;
+
+  /**
+   * Parse the given selector string into a servo SelectorList.
+   *
+   * Never returns null if aRv is not failing.
+   *
+   * Note that the selector list returned here is owned by the owner doc's
+   * selector cache.
+   */
+  const mozilla::StyleSelectorList* ParseSelectorList(
+      const nsACString& aSelectorString, mozilla::ErrorResult&);
+
+ public:
+  /* Event stuff that documents and elements share.
+
+     Note that we include DOCUMENT_ONLY_EVENT events here so that we
+     can forward all the document stuff to this implementation.
+  */
+#define EVENT(name_, id_, type_, struct_)                         \
+  mozilla::dom::EventHandlerNonNull* GetOn##name_() {             \
+    return GetEventHandler(nsGkAtoms::on##name_);                 \
+  }                                                               \
+  void SetOn##name_(mozilla::dom::EventHandlerNonNull* handler) { \
+    SetEventHandler(nsGkAtoms::on##name_, handler);               \
+  }
+#define TOUCH_EVENT EVENT
+#define DOCUMENT_ONLY_EVENT EVENT
+#include "mozilla/EventNameList.h"
+#undef DOCUMENT_ONLY_EVENT
+#undef TOUCH_EVENT
+#undef EVENT
+
+  NodeSelectorFlags GetSelectorFlags() const {
+    return static_cast<NodeSelectorFlags>(mSelectorFlags.Get());
+  }
+
+ protected:
+  static bool Traverse(nsINode* tmp, nsCycleCollectionTraversalCallback& cb);
+  static void Unlink(nsINode* tmp);
+
+  RefPtr<mozilla::dom::NodeInfo> mNodeInfo;
+
+  // mParent is an owning ref most of the time, except for the case of document
+  // nodes, so it cannot be represented by nsCOMPtr, so mark is as
+  // MOZ_OWNING_REF.
+  nsINode* MOZ_OWNING_REF mParent;
+
+ private:
+#ifndef BOOL_FLAGS_ON_WRAPPER_CACHE
+  // Boolean flags.
+  uint32_t mBoolFlags;
+#endif
+
+  mozilla::RustCell<uint32_t> mSelectorFlags{0};
+
+  uint32_t mChildCount;
+
+ protected:
+  // mNextSibling and mFirstChild are strong references while
+  // mPreviousOrLastSibling is a weak ref. |mFirstChild->mPreviousOrLastSibling|
+  // points to the last child node.
+  nsCOMPtr<nsIContent> mFirstChild;
+  nsCOMPtr<nsIContent> mNextSibling;
+  nsIContent* MOZ_NON_OWNING_REF mPreviousOrLastSibling;
+
+  union {
+    // Pointer to our primary frame.  Might be null.
+    nsIFrame* mPrimaryFrame;
+
+    // Pointer to the root of our subtree.  Might be null.
+    // This reference is non-owning and safe, since it either points to the
+    // object itself, or is reset by ClearSubtreeRootPointer.
+    nsINode* MOZ_NON_OWNING_REF mSubtreeRoot;
+  };
+
+  // Storage for more members that are usually not needed; allocated lazily.
+  nsSlots* mSlots;
+};
+
+NON_VIRTUAL_ADDREF_RELEASE(nsINode)
+
+inline nsINode* mozilla::dom::EventTarget::GetAsNode() {
+  return IsNode() ? AsNode() : nullptr;
+}
+
+inline const nsINode* mozilla::dom::EventTarget::GetAsNode() const {
+  return const_cast<mozilla::dom::EventTarget*>(this)->GetAsNode();
+}
+
+inline nsINode* mozilla::dom::EventTarget::AsNode() {
+  MOZ_DIAGNOSTIC_ASSERT(IsNode());
+  return static_cast<nsINode*>(this);
+}
+
+inline const nsINode* mozilla::dom::EventTarget::AsNode() const {
+  MOZ_DIAGNOSTIC_ASSERT(IsNode());
+  return static_cast<const nsINode*>(this);
+}
+
+// Useful inline function for getting a node given an nsIContent and a Document.
+// Returns the first argument cast to nsINode if it is non-null, otherwise
+// returns the second (which may be null).  We use type variables instead of
+// nsIContent* and Document* because the actual types must be
+// known for the cast to work.
+template <class C, class D>
+inline nsINode* NODE_FROM(C& aContent, D& aDocument) {
+  if (aContent) return static_cast<nsINode*>(aContent);
+  return static_cast<nsINode*>(aDocument);
+}
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsINode, NS_INODE_IID)
+
+inline nsISupports* ToSupports(nsINode* aPointer) { return aPointer; }
+
+// Some checks are faster to do on nsIContent or Element than on
+// nsINode, so spit out FromNode versions taking those types too.
+#define NS_IMPL_FROMNODE_GENERIC(_class, _check, _const)                 \
+  template <typename T>                                                  \
+  static auto FromNode(_const T& aNode)                                  \
+      -> decltype(static_cast<_const _class*>(&aNode)) {                 \
+    return aNode._check ? static_cast<_const _class*>(&aNode) : nullptr; \
+  }                                                                      \
+  template <typename T>                                                  \
+  static _const _class* FromNode(_const T* aNode) {                      \
+    return FromNode(*aNode);                                             \
+  }                                                                      \
+  template <typename T>                                                  \
+  static _const _class* FromNodeOrNull(_const T* aNode) {                \
+    return aNode ? FromNode(*aNode) : nullptr;                           \
+  }                                                                      \
+  template <typename T>                                                  \
+  static auto FromEventTarget(_const T& aEventTarget)                    \
+      -> decltype(static_cast<_const _class*>(&aEventTarget)) {          \
+    return aEventTarget.IsNode() && aEventTarget.AsNode()->_check        \
+               ? static_cast<_const _class*>(&aEventTarget)              \
+               : nullptr;                                                \
+  }                                                                      \
+  template <typename T>                                                  \
+  static _const _class* FromEventTarget(_const T* aEventTarget) {        \
+    return FromEventTarget(*aEventTarget);                               \
+  }                                                                      \
+  template <typename T>                                                  \
+  static _const _class* FromEventTargetOrNull(_const T* aEventTarget) {  \
+    return aEventTarget ? FromEventTarget(*aEventTarget) : nullptr;      \
+  }
+
+#define NS_IMPL_FROMNODE_HELPER(_class, _check)                                \
+  NS_IMPL_FROMNODE_GENERIC(_class, _check, )                                   \
+  NS_IMPL_FROMNODE_GENERIC(_class, _check, const)                              \
+                                                                               \
+  template <typename T>                                                        \
+  static _class* FromNode(T&& aNode) {                                         \
+    /* We need the double-cast in case aNode is a smartptr.  Those */          \
+    /* can cast to superclasses of the type they're templated on, */           \
+    /* but not directly to subclasses.  */                                     \
+    return aNode->_check ? static_cast<_class*>(static_cast<nsINode*>(aNode))  \
+                         : nullptr;                                            \
+  }                                                                            \
+  template <typename T>                                                        \
+  static _class* FromNodeOrNull(T&& aNode) {                                   \
+    return aNode ? FromNode(aNode) : nullptr;                                  \
+  }                                                                            \
+  template <typename T>                                                        \
+  static _class* FromEventTarget(T&& aEventTarget) {                           \
+    /* We need the double-cast in case aEventTarget is a smartptr.  Those */   \
+    /* can cast to superclasses of the type they're templated on, */           \
+    /* but not directly to subclasses.  */                                     \
+    return aEventTarget->IsNode() && aEventTarget->AsNode()->_check            \
+               ? static_cast<_class*>(static_cast<EventTarget*>(aEventTarget)) \
+               : nullptr;                                                      \
+  }                                                                            \
+  template <typename T>                                                        \
+  static _class* FromEventTargetOrNull(T&& aEventTarget) {                     \
+    return aEventTarget ? FromEventTarget(aEventTarget) : nullptr;             \
+  }
+
+#define NS_IMPL_FROMNODE(_class, _nsid) \
+  NS_IMPL_FROMNODE_HELPER(_class, IsInNamespace(_nsid))
+
+#define NS_IMPL_FROMNODE_WITH_TAG(_class, _nsid, _tag) \
+  NS_IMPL_FROMNODE_HELPER(_class, NodeInfo()->Equals(nsGkAtoms::_tag, _nsid))
+
+#define NS_IMPL_FROMNODE_HTML_WITH_TAG(_class, _tag) \
+  NS_IMPL_FROMNODE_WITH_TAG(_class, kNameSpaceID_XHTML, _tag)
+
+#endif /* nsINode_h___ */