Adding upstream version 124.0.1.upstream/124.0.1

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

1 files changed, 2291 insertions, 0 deletions

diff --git a/dom/base/Element.h b/dom/base/Element.h
new file mode 100644
index 0000000000..6c717bfc88
--- /dev/null
+++ b/dom/base/Element.h
@@ -0,0 +1,2291 @@
+/* -*- 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/. */
+
+/*
+ * Base class for all element classes; this provides an implementation
+ * of DOM Core's Element, implements nsIContent, provides
+ * utility methods for subclasses, and so forth.
+ */
+
+#ifndef mozilla_dom_Element_h__
+#define mozilla_dom_Element_h__
+
+#include <cstdio>
+#include <cstdint>
+#include <cstdlib>
+#include <utility>
+#include "AttrArray.h"
+#include "ErrorList.h"
+#include "Units.h"
+#include "js/RootingAPI.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/BasicEvents.h"
+#include "mozilla/CORSMode.h"
+#include "mozilla/FlushType.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/PseudoStyleType.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/Result.h"
+#include "mozilla/RustCell.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/dom/BorrowedAttrInfo.h"
+#include "mozilla/dom/DOMString.h"
+#include "mozilla/dom/DOMTokenListSupportedTokens.h"
+#include "mozilla/dom/DirectionalityUtils.h"
+#include "mozilla/dom/FragmentOrElement.h"
+#include "mozilla/dom/NameSpaceConstants.h"
+#include "mozilla/dom/NodeInfo.h"
+#include "mozilla/dom/RustTypes.h"
+#include "mozilla/dom/ShadowRootBinding.h"
+#include "nsAtom.h"
+#include "nsAttrValue.h"
+#include "nsAttrValueInlines.h"
+#include "nsCaseTreatment.h"
+#include "nsChangeHint.h"
+#include "nsTHashMap.h"
+#include "nsDebug.h"
+#include "nsError.h"
+#include "nsGkAtoms.h"
+#include "nsHashKeys.h"
+#include "nsIContent.h"
+#include "nsID.h"
+#include "nsINode.h"
+#include "nsLiteralString.h"
+#include "nsRect.h"
+#include "nsString.h"
+#include "nsStringFlags.h"
+#include "nsTLiteralString.h"
+#include "nscore.h"
+
+class JSObject;
+class mozAutoDocUpdate;
+class nsAttrName;
+class nsAttrValueOrString;
+class nsContentList;
+class nsDOMAttributeMap;
+class nsDOMCSSAttributeDeclaration;
+class nsDOMStringMap;
+class nsDOMTokenList;
+class nsFocusManager;
+class nsGenericHTMLFormControlElementWithState;
+class nsGlobalWindowInner;
+class nsGlobalWindowOuter;
+class nsImageLoadingContent;
+class nsIAutoCompletePopup;
+class nsIBrowser;
+class nsIDOMXULButtonElement;
+class nsIDOMXULContainerElement;
+class nsIDOMXULContainerItemElement;
+class nsIDOMXULControlElement;
+class nsIDOMXULMenuListElement;
+class nsIDOMXULMultiSelectControlElement;
+class nsIDOMXULRadioGroupElement;
+class nsIDOMXULRelatedElement;
+class nsIDOMXULSelectControlElement;
+class nsIDOMXULSelectControlItemElement;
+class nsIFrame;
+class nsIHTMLCollection;
+class nsIMozBrowserFrame;
+class nsIPrincipal;
+class nsIScreen;
+class nsIScrollableFrame;
+class nsIURI;
+class nsObjectLoadingContent;
+class nsPresContext;
+class nsWindowSizes;
+struct JSContext;
+struct ServoNodeData;
+template <class E>
+class nsTArray;
+template <class T>
+class nsGetterAddRefs;
+
+namespace mozilla {
+class DeclarationBlock;
+class MappedDeclarationsBuilder;
+class EditorBase;
+class ErrorResult;
+class OOMReporter;
+class SMILAttr;
+struct MutationClosureData;
+class TextEditor;
+namespace css {
+struct URLValue;
+}  // namespace css
+namespace dom {
+struct CheckVisibilityOptions;
+struct CustomElementData;
+struct SetHTMLOptions;
+struct GetAnimationsOptions;
+struct ScrollIntoViewOptions;
+struct ScrollToOptions;
+struct FocusOptions;
+struct ShadowRootInit;
+struct ScrollOptions;
+class Attr;
+class BooleanOrScrollIntoViewOptions;
+class Document;
+class HTMLFormElement;
+class DOMIntersectionObserver;
+class DOMMatrixReadOnly;
+class Element;
+class ElementOrCSSPseudoElement;
+class PopoverData;
+class Promise;
+class Sanitizer;
+class ShadowRoot;
+class UnrestrictedDoubleOrKeyframeAnimationOptions;
+template <typename T>
+class Optional;
+enum class CallerType : uint32_t;
+enum class ReferrerPolicy : uint8_t;
+typedef nsTHashMap<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>
+    IntersectionObserverList;
+}  // namespace dom
+}  // namespace mozilla
+
+using nsMapRuleToAttributesFunc = void (*)(mozilla::MappedDeclarationsBuilder&);
+
+// Declared here because of include hell.
+extern "C" bool Servo_Element_IsDisplayContents(const mozilla::dom::Element*);
+
+already_AddRefed<nsContentList> NS_GetContentList(nsINode* aRootNode,
+                                                  int32_t aMatchNameSpaceId,
+                                                  const nsAString& aTagname);
+
+#define ELEMENT_FLAG_BIT(n_) \
+  NODE_FLAG_BIT(NODE_TYPE_SPECIFIC_BITS_OFFSET + (n_))
+
+// Element-specific flags
+enum : uint32_t {
+  // Whether this node has dirty descendants for Servo's style system.
+  ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO = ELEMENT_FLAG_BIT(0),
+  // Whether this node has dirty descendants for animation-only restyle for
+  // Servo's style system.
+  ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO = ELEMENT_FLAG_BIT(1),
+
+  // Whether the element has been snapshotted due to attribute or state changes
+  // by the Servo restyle manager.
+  ELEMENT_HAS_SNAPSHOT = ELEMENT_FLAG_BIT(2),
+
+  // Whether the element has already handled its relevant snapshot.
+  //
+  // Used by the servo restyle process in order to accurately track whether the
+  // style of an element is up-to-date, even during the same restyle process.
+  ELEMENT_HANDLED_SNAPSHOT = ELEMENT_FLAG_BIT(3),
+
+  // If this flag is set on an element, that means that it is a HTML datalist
+  // element or has a HTML datalist element ancestor.
+  ELEMENT_IS_DATALIST_OR_HAS_DATALIST_ANCESTOR = ELEMENT_FLAG_BIT(4),
+
+  // If this flag is set on an element, that means this element
+  // has been considered by our LargestContentfulPaint algorithm and
+  // it's not going to be considered again.
+  ELEMENT_PROCESSED_BY_LCP_FOR_TEXT = ELEMENT_FLAG_BIT(5),
+
+  // If this flag is set on an element, this means the HTML parser encountered
+  // a duplicate attribute error:
+  // https://html.spec.whatwg.org/multipage/parsing.html#parse-error-duplicate-attribute
+  // This flag is used for detecting dangling markup attacks in the CSP
+  // algorithm https://w3c.github.io/webappsec-csp/#is-element-nonceable.
+  ELEMENT_PARSER_HAD_DUPLICATE_ATTR_ERROR = ELEMENT_FLAG_BIT(6),
+
+  // Remaining bits are for subclasses
+  ELEMENT_TYPE_SPECIFIC_BITS_OFFSET = NODE_TYPE_SPECIFIC_BITS_OFFSET + 7
+};
+
+#undef ELEMENT_FLAG_BIT
+
+// Make sure we have space for our bits
+ASSERT_NODE_FLAGS_SPACE(ELEMENT_TYPE_SPECIFIC_BITS_OFFSET);
+
+namespace mozilla {
+enum class PseudoStyleType : uint8_t;
+class EventChainPostVisitor;
+class EventChainPreVisitor;
+class EventChainVisitor;
+class EventListenerManager;
+class EventStateManager;
+
+namespace dom {
+
+struct CustomElementDefinition;
+class Animation;
+class CustomElementRegistry;
+class Link;
+class DOMRect;
+class DOMRectList;
+class Flex;
+class Grid;
+
+// IID for the dom::Element interface
+#define NS_ELEMENT_IID                               \
+  {                                                  \
+    0xc67ed254, 0xfd3b, 0x4b10, {                    \
+      0x96, 0xa2, 0xc5, 0x8b, 0x7b, 0x64, 0x97, 0xd1 \
+    }                                                \
+  }
+
+#define REFLECT_NULLABLE_DOMSTRING_ATTR(method, attr)            \
+  void Get##method(nsAString& aValue) const {                    \
+    const nsAttrValue* val = mAttrs.GetAttr(nsGkAtoms::attr);    \
+    if (!val) {                                                  \
+      SetDOMStringToNull(aValue);                                \
+      return;                                                    \
+    }                                                            \
+    val->ToString(aValue);                                       \
+  }                                                              \
+  void Set##method(const nsAString& aValue, ErrorResult& aRv) {  \
+    SetOrRemoveNullableStringAttr(nsGkAtoms::attr, aValue, aRv); \
+  }
+
+class Element : public FragmentOrElement {
+ public:
+#ifdef MOZILLA_INTERNAL_API
+  explicit Element(already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo)
+      : FragmentOrElement(std::move(aNodeInfo)),
+        mState(ElementState::READONLY | ElementState::DEFINED) {
+    MOZ_ASSERT(mNodeInfo->NodeType() == ELEMENT_NODE,
+               "Bad NodeType in aNodeInfo");
+    SetIsElement();
+  }
+
+  ~Element() {
+    NS_ASSERTION(!HasServoData(), "expected ServoData to be cleared earlier");
+  }
+
+#endif  // MOZILLA_INTERNAL_API
+
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_ELEMENT_IID)
+
+  NS_DECL_ADDSIZEOFEXCLUDINGTHIS
+
+  NS_IMPL_FROMNODE_HELPER(Element, IsElement())
+
+  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
+
+  /**
+   * Method to get the full state of this element. See dom/base/rust/lib.rs for
+   * the possible bits that could be set here.
+   */
+  ElementState State() const { return mState; }
+
+  /**
+   * Returns the current disabled state of the element.
+   */
+  bool IsDisabled() const { return State().HasState(ElementState::DISABLED); }
+  bool IsReadOnly() const { return State().HasState(ElementState::READONLY); }
+  bool IsDisabledOrReadOnly() const {
+    return State().HasAtLeastOneOfStates(ElementState::DISABLED |
+                                         ElementState::READONLY);
+  }
+
+  virtual int32_t TabIndexDefault() { return -1; }
+
+  /**
+   * Get tabIndex of this element. If not found, return TabIndexDefault.
+   */
+  int32_t TabIndex();
+
+  /**
+   * Get the parsed value of tabindex attribute.
+   */
+  Maybe<int32_t> GetTabIndexAttrValue();
+
+  /**
+   * Set tabIndex value to this element.
+   */
+  void SetTabIndex(int32_t aTabIndex, mozilla::ErrorResult& aError);
+
+  /**
+   * Sets the ShadowRoot binding for this element. The contents of the
+   * binding is rendered in place of this node's children.
+   *
+   * @param aShadowRoot The ShadowRoot to be bound to this element.
+   */
+  void SetShadowRoot(ShadowRoot* aShadowRoot);
+
+  void SetLastRememberedBSize(float aBSize);
+  void SetLastRememberedISize(float aISize);
+  void RemoveLastRememberedBSize();
+  void RemoveLastRememberedISize();
+
+  /**
+   * Make focus on this element.
+   */
+  // TODO: Convert Focus() to MOZ_CAN_RUN_SCRIPT and get rid of the
+  //       kungFuDeathGrip in it.
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY virtual void Focus(const FocusOptions& aOptions,
+                                                 const CallerType aCallerType,
+                                                 ErrorResult& aError);
+
+  /**
+   * Show blur and clear focus.
+   */
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY virtual void Blur(mozilla::ErrorResult& aError);
+
+  /**
+   * The style state of this element. This is the real state of the element
+   * with any style locks applied for pseudo-class inspecting.
+   */
+  ElementState StyleState() const {
+    if (!HasLockedStyleStates()) {
+      return mState;
+    }
+    return StyleStateFromLocks();
+  }
+
+  /**
+   * StyleStateLocks is used to specify which event states should be locked,
+   * and whether they should be locked to on or off.
+   */
+  struct StyleStateLocks {
+    // mLocks tracks which event states should be locked.
+    ElementState mLocks;
+    // mValues tracks if the locked state should be on or off.
+    ElementState mValues;
+  };
+
+  /**
+   * The style state locks applied to this element.
+   */
+  StyleStateLocks LockedStyleStates() const;
+
+  /**
+   * Add a style state lock on this element.
+   * aEnabled is the value to lock the given state bits to.
+   */
+  void LockStyleStates(ElementState aStates, bool aEnabled);
+
+  /**
+   * Remove a style state lock on this element.
+   */
+  void UnlockStyleStates(ElementState aStates);
+
+  /**
+   * Clear all style state locks on this element.
+   */
+  void ClearStyleStateLocks();
+
+  /**
+   * Accessors for the state of our dir attribute.
+   */
+  bool HasDirAuto() const {
+    return State().HasState(ElementState::HAS_DIR_ATTR_LIKE_AUTO);
+  }
+
+  /**
+   * Elements with dir="rtl" or dir="ltr".
+   */
+  bool HasFixedDir() const {
+    return State().HasAtLeastOneOfStates(ElementState::HAS_DIR_ATTR_LTR |
+                                         ElementState::HAS_DIR_ATTR_RTL);
+  }
+
+  /**
+   * Get the inline style declaration, if any, for this element.
+   */
+  DeclarationBlock* GetInlineStyleDeclaration() const;
+
+  /**
+   * Get the mapped attributes, if any, for this element.
+   */
+  StyleLockedDeclarationBlock* GetMappedAttributeStyle() const {
+    return mAttrs.GetMappedDeclarationBlock();
+  }
+
+  bool IsPendingMappedAttributeEvaluation() const {
+    return mAttrs.IsPendingMappedAttributeEvaluation();
+  }
+
+  void SetMappedDeclarationBlock(already_AddRefed<StyleLockedDeclarationBlock>);
+
+  /**
+   * InlineStyleDeclarationWillChange is called before SetInlineStyleDeclaration
+   * so that the element implementation can access the old style attribute
+   * value.
+   */
+  virtual void InlineStyleDeclarationWillChange(MutationClosureData& aData);
+
+  /**
+   * Set the inline style declaration for this element.
+   */
+  virtual nsresult SetInlineStyleDeclaration(DeclarationBlock& aDeclaration,
+                                             MutationClosureData& aData);
+
+  /**
+   * Get the SMIL override style declaration for this element. If the
+   * rule hasn't been created, this method simply returns null.
+   */
+  DeclarationBlock* GetSMILOverrideStyleDeclaration();
+
+  /**
+   * Set the SMIL override style declaration for this element. This method will
+   * notify the document's pres context, so that the style changes will be
+   * noticed.
+   */
+  void SetSMILOverrideStyleDeclaration(DeclarationBlock&);
+
+  /**
+   * Returns a new SMILAttr that allows the caller to animate the given
+   * attribute on this element.
+   */
+  virtual UniquePtr<SMILAttr> GetAnimatedAttr(int32_t aNamespaceID,
+                                              nsAtom* aName);
+
+  /**
+   * Get the SMIL override style for this element. This is a style declaration
+   * that is applied *after* the inline style, and it can be used e.g. to store
+   * animated style values.
+   *
+   * Note: This method is analogous to the 'GetStyle' method in
+   * nsGenericHTMLElement and nsStyledElement.
+   */
+  nsDOMCSSAttributeDeclaration* SMILOverrideStyle();
+
+  /**
+   * Returns if the element is labelable as per HTML specification.
+   */
+  virtual bool IsLabelable() const;
+
+  /**
+   * Returns if the element is interactive content as per HTML specification.
+   */
+  virtual bool IsInteractiveHTMLContent() const;
+
+  /**
+   * Returns |this| as an nsIMozBrowserFrame* if the element is a frame or
+   * iframe element.
+   *
+   * We have this method, rather than using QI, so that we can use it during
+   * the servo traversal, where we can't QI DOM nodes because of non-thread-safe
+   * refcounts.
+   */
+  virtual nsIMozBrowserFrame* GetAsMozBrowserFrame() { return nullptr; }
+
+  /**
+   * Is the attribute named aAttribute a mapped attribute?
+   */
+  NS_IMETHOD_(bool) IsAttributeMapped(const nsAtom* aAttribute) const;
+
+  nsresult BindToTree(BindContext&, nsINode& aParent) override;
+  void UnbindFromTree(bool aNullParent = true) override;
+
+  virtual nsMapRuleToAttributesFunc GetAttributeMappingFunction() const;
+  static void MapNoAttributesInto(mozilla::MappedDeclarationsBuilder&);
+
+  /**
+   * Get a hint that tells the style system what to do when
+   * an attribute on this node changes, if something needs to happen
+   * in response to the change *other* than the result of what is
+   * mapped into style data via any type of style rule.
+   */
+  virtual nsChangeHint GetAttributeChangeHint(const nsAtom* aAttribute,
+                                              int32_t aModType) const;
+
+  inline Directionality GetDirectionality() const {
+    ElementState state = State();
+    if (state.HasState(ElementState::RTL)) {
+      return Directionality::Rtl;
+    }
+    if (state.HasState(ElementState::LTR)) {
+      return Directionality::Ltr;
+    }
+    return Directionality::Unset;
+  }
+
+  inline void SetDirectionality(Directionality aDir, bool aNotify) {
+    AutoStateChangeNotifier notifier(*this, aNotify);
+    RemoveStatesSilently(ElementState::DIR_STATES);
+    switch (aDir) {
+      case Directionality::Rtl:
+        AddStatesSilently(ElementState::RTL);
+        break;
+      case Directionality::Ltr:
+        AddStatesSilently(ElementState::LTR);
+        break;
+      case Directionality::Unset:
+      case Directionality::Auto:
+        MOZ_ASSERT_UNREACHABLE("Setting unresolved directionality?");
+        break;
+    }
+  }
+
+  Directionality GetComputedDirectionality() const;
+
+  static const uint32_t kAllServoDescendantBits =
+      ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO |
+      ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO |
+      NODE_DESCENDANTS_NEED_FRAMES;
+
+  /**
+   * Notes that something in the given subtree of this element needs dirtying,
+   * and that all the relevant dirty bits have already been propagated up to the
+   * element.
+   *
+   * This is important because `NoteDirtyForServo` uses the dirty bits to reason
+   * about the shape of the tree, so we can't just call into there.
+   */
+  void NoteDirtySubtreeForServo();
+
+  void NoteDirtyForServo();
+  void NoteAnimationOnlyDirtyForServo();
+  void NoteDescendantsNeedFramesForServo();
+
+  bool HasDirtyDescendantsForServo() const {
+    return HasFlag(ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO);
+  }
+
+  void SetHasDirtyDescendantsForServo() {
+    SetFlags(ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO);
+  }
+
+  void UnsetHasDirtyDescendantsForServo() {
+    UnsetFlags(ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO);
+  }
+
+  bool HasAnimationOnlyDirtyDescendantsForServo() const {
+    return HasFlag(ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO);
+  }
+
+  void SetHasAnimationOnlyDirtyDescendantsForServo() {
+    SetFlags(ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO);
+  }
+
+  void UnsetHasAnimationOnlyDirtyDescendantsForServo() {
+    UnsetFlags(ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO);
+  }
+
+  bool HasServoData() const { return !!mServoData.Get(); }
+
+  void ClearServoData() { ClearServoData(GetComposedDoc()); }
+  void ClearServoData(Document* aDocument);
+
+  PopoverData* GetPopoverData() const {
+    const nsExtendedDOMSlots* slots = GetExistingExtendedDOMSlots();
+    return slots ? slots->mPopoverData.get() : nullptr;
+  }
+
+  PopoverData& EnsurePopoverData() {
+    if (auto* popoverData = GetPopoverData()) {
+      return *popoverData;
+    }
+    return CreatePopoverData();
+  }
+
+  bool IsAutoPopover() const;
+  bool IsPopoverOpen() const;
+
+  /**
+   * https://html.spec.whatwg.org/multipage/popover.html#topmost-popover-ancestor
+   */
+  Element* GetTopmostPopoverAncestor(const Element* aInvoker,
+                                     bool isPopover) const;
+
+  ElementAnimationData* GetAnimationData() const {
+    if (!MayHaveAnimations()) {
+      return nullptr;
+    }
+    const nsExtendedDOMSlots* slots = GetExistingExtendedDOMSlots();
+    return slots ? slots->mAnimations.get() : nullptr;
+  }
+
+  ElementAnimationData& EnsureAnimationData() {
+    if (auto* anim = GetAnimationData()) {
+      return *anim;
+    }
+    return CreateAnimationData();
+  }
+
+ private:
+  ElementAnimationData& CreateAnimationData();
+  PopoverData& CreatePopoverData();
+
+ public:
+  void ClearPopoverData();
+
+  /**
+   * Gets the custom element data used by web components custom element.
+   * Custom element data is created at the first attempt to enqueue a callback.
+   *
+   * @return The custom element data or null if none.
+   */
+  CustomElementData* GetCustomElementData() const {
+    if (!HasCustomElementData()) {
+      return nullptr;
+    }
+
+    const nsExtendedDOMSlots* slots = GetExistingExtendedDOMSlots();
+    return slots ? slots->mCustomElementData.get() : nullptr;
+  }
+
+  /**
+   * Sets the custom element data, ownership of the
+   * callback data is taken by this element.
+   *
+   * @param aData The custom element data.
+   */
+  void SetCustomElementData(UniquePtr<CustomElementData> aData);
+
+  nsTArray<RefPtr<nsAtom>>& EnsureCustomStates();
+
+  /**
+   * Gets the custom element definition used by web components custom element.
+   *
+   * @return The custom element definition or null if element is not a custom
+   *         element or custom element is not defined yet.
+   */
+  CustomElementDefinition* GetCustomElementDefinition() const;
+
+  /**
+   * Sets the custom element definition, called when custom element is created
+   * or upgraded.
+   *
+   * @param aDefinition The custom element definition.
+   */
+  virtual void SetCustomElementDefinition(CustomElementDefinition* aDefinition);
+
+  const AttrArray& GetAttrs() const { return mAttrs; }
+
+  void SetDefined(bool aSet) { SetStates(ElementState::DEFINED, aSet); }
+
+  // AccessibilityRole
+  REFLECT_NULLABLE_DOMSTRING_ATTR(Role, role)
+
+  // AriaAttributes
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaAtomic, aria_atomic)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaAutoComplete, aria_autocomplete)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaBusy, aria_busy)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaChecked, aria_checked)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaColCount, aria_colcount)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaColIndex, aria_colindex)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaColIndexText, aria_colindextext)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaColSpan, aria_colspan)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaCurrent, aria_current)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaDescription, aria_description)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaDisabled, aria_disabled)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaExpanded, aria_expanded)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaHasPopup, aria_haspopup)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaHidden, aria_hidden)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaInvalid, aria_invalid)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaKeyShortcuts, aria_keyshortcuts)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaLabel, aria_label)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaLevel, aria_level)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaLive, aria_live)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaModal, aria_modal)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaMultiLine, aria_multiline)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaMultiSelectable, aria_multiselectable)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaOrientation, aria_orientation)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaPlaceholder, aria_placeholder)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaPosInSet, aria_posinset)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaPressed, aria_pressed)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaReadOnly, aria_readonly)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRelevant, aria_relevant)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRequired, aria_required)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRoleDescription, aria_roledescription)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRowCount, aria_rowcount)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRowIndex, aria_rowindex)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRowIndexText, aria_rowindextext)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRowSpan, aria_rowspan)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaSelected, aria_selected)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaSetSize, aria_setsize)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaSort, aria_sort)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaValueMax, aria_valuemax)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaValueMin, aria_valuemin)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaValueNow, aria_valuenow)
+  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaValueText, aria_valuetext)
+
+ protected:
+  already_AddRefed<ShadowRoot> AttachShadowInternal(ShadowRootMode,
+                                                    ErrorResult& aError);
+
+ public:
+  MOZ_CAN_RUN_SCRIPT
+  nsIScrollableFrame* GetScrollFrame(nsIFrame** aFrame = nullptr,
+                                     FlushType aFlushType = FlushType::Layout);
+
+ private:
+  // Style state computed from element's state and style locks.
+  ElementState StyleStateFromLocks() const;
+
+  void NotifyStateChange(ElementState aStates);
+  void NotifyStyleStateChange(ElementState aStates);
+
+ public:
+  struct AutoStateChangeNotifier {
+    AutoStateChangeNotifier(Element& aElement, bool aNotify)
+        : mElement(aElement), mOldState(aElement.State()), mNotify(aNotify) {}
+    ~AutoStateChangeNotifier() {
+      if (!mNotify) {
+        return;
+      }
+      ElementState newState = mElement.State();
+      if (mOldState != newState) {
+        mElement.NotifyStateChange(mOldState ^ newState);
+      }
+    }
+
+   private:
+    Element& mElement;
+    const ElementState mOldState;
+    const bool mNotify;
+  };
+
+  // Method to add state bits.  This should be called from subclass constructors
+  // to set up our event state correctly at construction time, and other places
+  // where we don't want to notify a state change, or there's an
+  // AutoStateChangeNotifier on the stack.
+  void AddStatesSilently(ElementState aStates) { mState |= aStates; }
+  // Method to remove state bits.  This should be called from subclass
+  // constructors to set up our event state correctly at construction time and
+  // other places where we don't want to notify a state change.
+  void RemoveStatesSilently(ElementState aStates) { mState &= ~aStates; }
+  // Methods to add state bits, potentially notifying. These will handle setting
+  // up script blockers when they notify, so no need to do it in the callers
+  // unless desired. States passed here must only be those in
+  // EXTERNALLY_MANAGED_STATES.
+  void AddStates(ElementState aStates, bool aNotify = true) {
+    ElementState old = mState;
+    AddStatesSilently(aStates);
+    if (aNotify && old != mState) {
+      NotifyStateChange(old ^ mState);
+    }
+  }
+  void RemoveStates(ElementState aStates, bool aNotify = true) {
+    ElementState old = mState;
+    RemoveStatesSilently(aStates);
+    if (aNotify && old != mState) {
+      NotifyStateChange(old ^ mState);
+    }
+  }
+  void SetStates(ElementState aStates, bool aSet, bool aNotify = true) {
+    if (aSet) {
+      AddStates(aStates, aNotify);
+    } else {
+      RemoveStates(aStates, aNotify);
+    }
+  }
+  void ToggleStates(ElementState aStates, bool aNotify) {
+    mState ^= aStates;
+    if (aNotify) {
+      NotifyStateChange(aStates);
+    }
+  }
+
+  void UpdateEditableState(bool aNotify) override;
+  // Makes sure that the READONLY/READWRITE flags are in sync.
+  void UpdateReadOnlyState(bool aNotify);
+  // Form controls and non-form controls should have different :read-only /
+  // :read-write behavior. This is what effectively controls it.
+  virtual bool IsReadOnlyInternal() const;
+
+  /**
+   * Normalizes an attribute name and returns it as a nodeinfo if an attribute
+   * with that name exists. This method is intended for character case
+   * conversion if the content object is case insensitive (e.g. HTML). Returns
+   * the nodeinfo of the attribute with the specified name if one exists or
+   * null otherwise.
+   *
+   * @param aStr the unparsed attribute string
+   * @return the node info. May be nullptr.
+   */
+  already_AddRefed<mozilla::dom::NodeInfo> GetExistingAttrNameFromQName(
+      const nsAString& aStr) const;
+
+  /**
+   * Helper for SetAttr/SetParsedAttr. This method will return true if aNotify
+   * is true or there are mutation listeners that must be triggered, the
+   * attribute is currently set, and the new value that is about to be set is
+   * different to the current value. As a perf optimization the new and old
+   * values will not actually be compared if we aren't notifying and we don't
+   * have mutation listeners (in which case it's cheap to just return false
+   * and let the caller go ahead and set the value).
+   * @param aOldValue [out] Set to the old value of the attribute, but only if
+   *   there are event listeners. If set, the type of aOldValue will be either
+   *   nsAttrValue::eString or nsAttrValue::eAtom.
+   * @param aModType [out] Set to MutationEvent_Binding::MODIFICATION or to
+   *   MutationEvent_Binding::ADDITION, but only if this helper returns true
+   * @param aHasListeners [out] Set to true if there are mutation event
+   *   listeners listening for NS_EVENT_BITS_MUTATION_ATTRMODIFIED
+   * @param aOldValueSet [out] Indicates whether an old attribute value has been
+   *   stored in aOldValue. The bool will be set to true if a value was stored.
+   */
+  bool MaybeCheckSameAttrVal(int32_t aNamespaceID, const nsAtom* aName,
+                             const nsAtom* aPrefix,
+                             const nsAttrValueOrString& aValue, bool aNotify,
+                             nsAttrValue& aOldValue, uint8_t* aModType,
+                             bool* aHasListeners, bool* aOldValueSet);
+
+  /**
+   * Notifies mutation listeners if aNotify is true, there are mutation
+   * listeners, and the attribute value is changing.
+   *
+   * @param aNamespaceID The namespace of the attribute
+   * @param aName The local name of the attribute
+   * @param aPrefix The prefix of the attribute
+   * @param aValue The value that the attribute is being changed to
+   * @param aNotify If true, mutation listeners will be notified if they exist
+   *   and the attribute value is changing
+   * @param aOldValue [out] Set to the old value of the attribute, but only if
+   *   there are event listeners. If set, the type of aOldValue will be either
+   *   nsAttrValue::eString or nsAttrValue::eAtom.
+   * @param aModType [out] Set to MutationEvent_Binding::MODIFICATION or to
+   *   MutationEvent_Binding::ADDITION, but only if this helper returns true
+   * @param aHasListeners [out] Set to true if there are mutation event
+   *   listeners listening for NS_EVENT_BITS_MUTATION_ATTRMODIFIED
+   * @param aOldValueSet [out] Indicates whether an old attribute value has been
+   *   stored in aOldValue. The bool will be set to true if a value was stored.
+   */
+  bool OnlyNotifySameValueSet(int32_t aNamespaceID, nsAtom* aName,
+                              nsAtom* aPrefix,
+                              const nsAttrValueOrString& aValue, bool aNotify,
+                              nsAttrValue& aOldValue, uint8_t* aModType,
+                              bool* aHasListeners, bool* aOldValueSet);
+
+  /**
+   * Sets the class attribute.
+   * Assumes that we are not notifying and that the attribute hasn't been
+   * set previously.
+   */
+  nsresult SetClassAttrFromParser(nsAtom* aValue);
+
+  // aParsedValue receives the old value of the attribute. That's useful if
+  // either the input or output value of aParsedValue is StoresOwnData.
+  nsresult SetParsedAttr(int32_t aNameSpaceID, nsAtom* aName, nsAtom* aPrefix,
+                         nsAttrValue& aParsedValue, bool aNotify);
+  /**
+   * Get the current value of the attribute. This returns a form that is
+   * suitable for passing back into SetAttr.
+   *
+   * @param aNameSpaceID the namespace of the attr (defaults to
+                         kNameSpaceID_None in the overload that omits this arg)
+   * @param aName the name of the attr
+   * @param aResult the value (may legitimately be the empty string) [OUT]
+   * @returns true if the attribute was set (even when set to empty string)
+   *          false when not set.
+   * GetAttr is not inlined on purpose, to keep down codesize from all the
+   * inlined nsAttrValue bits for C++ callers.
+   */
+  bool GetAttr(int32_t aNameSpaceID, const nsAtom* aName,
+               nsAString& aResult) const;
+  bool GetAttr(const nsAtom* aName, nsAString& aResult) const;
+
+  /**
+   * Determine if an attribute has been set (empty string or otherwise).
+   *
+   * @param aNameSpaceId the namespace id of the attribute (defaults to
+                         kNameSpaceID_None in the overload that omits this arg)
+   * @param aAttr the attribute name
+   * @return whether an attribute exists
+   */
+  inline bool HasAttr(int32_t aNameSpaceID, const nsAtom* aName) const {
+    return mAttrs.HasAttr(aNameSpaceID, aName);
+  }
+
+  bool HasAttr(const nsAtom* aAttr) const { return mAttrs.HasAttr(aAttr); }
+
+  /**
+   * Determine if an attribute has been set to a non-empty string value. If the
+   * attribute is not set at all, this will return false.
+   *
+   * @param aNameSpaceId the namespace id of the attribute (defaults to
+   *                     kNameSpaceID_None in the overload that omits this arg)
+   * @param aAttr the attribute name
+   */
+  inline bool HasNonEmptyAttr(int32_t aNameSpaceID, const nsAtom* aName) const;
+
+  bool HasNonEmptyAttr(const nsAtom* aAttr) const {
+    return HasNonEmptyAttr(kNameSpaceID_None, aAttr);
+  }
+
+  /**
+   * Test whether this Element's given attribute has the given value.  If the
+   * attribute is not set at all, this will return false.
+   *
+   * @param aNameSpaceID The namespace ID of the attribute.  Must not
+   *                     be kNameSpaceID_Unknown.
+   * @param aName The name atom of the attribute.  Must not be null.
+   * @param aValue The value to compare to.
+   * @param aCaseSensitive Whether to do a case-sensitive compare on the value.
+   */
+  inline bool AttrValueIs(int32_t aNameSpaceID, const nsAtom* aName,
+                          const nsAString& aValue,
+                          nsCaseTreatment aCaseSensitive) const;
+
+  /**
+   * Test whether this Element's given attribute has the given value.  If the
+   * attribute is not set at all, this will return false.
+   *
+   * @param aNameSpaceID The namespace ID of the attribute.  Must not
+   *                     be kNameSpaceID_Unknown.
+   * @param aName The name atom of the attribute.  Must not be null.
+   * @param aValue The value to compare to.  Must not be null.
+   * @param aCaseSensitive Whether to do a case-sensitive compare on the value.
+   */
+  bool AttrValueIs(int32_t aNameSpaceID, const nsAtom* aName,
+                   const nsAtom* aValue, nsCaseTreatment aCaseSensitive) const;
+
+  /**
+   * Check whether this Element's given attribute has one of a given list of
+   * values. If there is a match, we return the index in the list of the first
+   * matching value. If there was no attribute at all, then we return
+   * ATTR_MISSING. If there was an attribute but it didn't match, we return
+   * ATTR_VALUE_NO_MATCH. A non-negative result always indicates a match.
+   *
+   * @param aNameSpaceID The namespace ID of the attribute.  Must not
+   *                     be kNameSpaceID_Unknown.
+   * @param aName The name atom of the attribute.  Must not be null.
+   * @param aValues a nullptr-terminated array of pointers to atom values to
+   * test against.
+   * @param aCaseSensitive Whether to do a case-sensitive compare on the values.
+   * @return ATTR_MISSING, ATTR_VALUE_NO_MATCH or the non-negative index
+   * indicating the first value of aValues that matched
+   */
+  using AttrValuesArray = AttrArray::AttrValuesArray;
+  int32_t FindAttrValueIn(int32_t aNameSpaceID, const nsAtom* aName,
+                          AttrArray::AttrValuesArray* aValues,
+                          nsCaseTreatment aCaseSensitive) const;
+
+  /**
+   * Set attribute values. All attribute values are assumed to have a
+   * canonical string representation that can be used for these
+   * methods. The SetAttr method is assumed to perform a translation
+   * of the canonical form into the underlying content specific
+   * form.
+   *
+   * @param aNameSpaceID the namespace of the attribute
+   * @param aName the name of the attribute
+   * @param aValue the value to set
+   * @param aNotify specifies how whether or not the document should be
+   *        notified of the attribute change.
+   */
+  nsresult SetAttr(int32_t aNameSpaceID, nsAtom* aName, const nsAString& aValue,
+                   bool aNotify) {
+    return SetAttr(aNameSpaceID, aName, nullptr, aValue, aNotify);
+  }
+  nsresult SetAttr(int32_t aNameSpaceID, nsAtom* aName, nsAtom* aPrefix,
+                   const nsAString& aValue, bool aNotify) {
+    return SetAttr(aNameSpaceID, aName, aPrefix, aValue, nullptr, aNotify);
+  }
+  nsresult SetAttr(int32_t aNameSpaceID, nsAtom* aName, const nsAString& aValue,
+                   nsIPrincipal* aTriggeringPrincipal, bool aNotify) {
+    return SetAttr(aNameSpaceID, aName, nullptr, aValue, aTriggeringPrincipal,
+                   aNotify);
+  }
+
+  /**
+   * Set attribute values. All attribute values are assumed to have a
+   * canonical String representation that can be used for these
+   * methods. The SetAttr method is assumed to perform a translation
+   * of the canonical form into the underlying content specific
+   * form.
+   *
+   * @param aNameSpaceID the namespace of the attribute
+   * @param aName the name of the attribute
+   * @param aPrefix the prefix of the attribute
+   * @param aValue the value to set
+   * @param aMaybeScriptedPrincipal the principal of the scripted caller
+   * responsible for setting the attribute, or null if no scripted caller can be
+   *        determined. A null value here does not guarantee that there is no
+   *        scripted caller, but a non-null value does guarantee that a scripted
+   *        caller with the given principal is directly responsible for the
+   *        attribute change.
+   * @param aNotify specifies how whether or not the document should be
+   *        notified of the attribute change.
+   */
+  nsresult SetAttr(int32_t aNameSpaceID, nsAtom* aName, nsAtom* aPrefix,
+                   const nsAString& aValue,
+                   nsIPrincipal* aMaybeScriptedPrincipal, bool aNotify);
+
+  /**
+   * Remove an attribute so that it is no longer explicitly specified.
+   *
+   * @param aNameSpaceID the namespace id of the attribute
+   * @param aName the name of the attribute to unset
+   * @param aNotify specifies whether or not the document should be
+   * notified of the attribute change
+   */
+  nsresult UnsetAttr(int32_t aNameSpaceID, nsAtom* aName, bool aNotify);
+
+  /**
+   * Get the namespace / name / prefix of a given attribute.
+   *
+   * @param   aIndex the index of the attribute name
+   * @returns The name at the given index, or null if the index is
+   *          out-of-bounds.
+   * @note    The document returned by NodeInfo()->GetDocument() (if one is
+   *          present) is *not* necessarily the owner document of the element.
+   * @note    The pointer returned by this function is only valid until the
+   *          next call of either GetAttrNameAt or SetAttr on the element.
+   */
+  const nsAttrName* GetAttrNameAt(uint32_t aIndex) const {
+    return mAttrs.GetSafeAttrNameAt(aIndex);
+  }
+
+  /**
+   * Same as above, but does not do out-of-bounds checks!
+   */
+  const nsAttrName* GetUnsafeAttrNameAt(uint32_t aIndex) const {
+    return mAttrs.AttrNameAt(aIndex);
+  }
+
+  /**
+   * Gets the attribute info (name and value) for this element at a given index.
+   */
+  BorrowedAttrInfo GetAttrInfoAt(uint32_t aIndex) const {
+    if (aIndex >= mAttrs.AttrCount()) {
+      return BorrowedAttrInfo(nullptr, nullptr);
+    }
+
+    return mAttrs.AttrInfoAt(aIndex);
+  }
+
+  /**
+   * Get the number of all specified attributes.
+   *
+   * @return the number of attributes
+   */
+  uint32_t GetAttrCount() const { return mAttrs.AttrCount(); }
+
+  /**
+   * Get the class list of this element (this corresponds to the value of the
+   * class attribute).  This may be null if there are no classes, but that's not
+   * guaranteed (e.g. we could have class="").
+   */
+  const nsAttrValue* GetClasses() const {
+    if (!MayHaveClass()) {
+      return nullptr;
+    }
+
+    if (IsSVGElement()) {
+      if (const nsAttrValue* value = GetSVGAnimatedClass()) {
+        return value;
+      }
+    }
+
+    return GetParsedAttr(nsGkAtoms::_class);
+  }
+
+#ifdef MOZ_DOM_LIST
+  virtual void List(FILE* out = stdout, int32_t aIndent = 0) const override {
+    List(out, aIndent, ""_ns);
+  }
+  virtual void DumpContent(FILE* out, int32_t aIndent,
+                           bool aDumpAll) const override;
+  void List(FILE* out, int32_t aIndent, const nsCString& aPrefix) const;
+  void ListAttributes(FILE* out) const;
+#endif
+
+  /**
+   * Append to aOutDescription a string describing the element and its
+   * attributes.
+   * If aShort is true, only the id and class attributes will be listed.
+   */
+  void Describe(nsAString& aOutDescription, bool aShort = false) const;
+
+  /*
+   * Attribute Mapping Helpers
+   */
+  struct MappedAttributeEntry {
+    const nsStaticAtom* const attribute;
+  };
+
+  /**
+   * A common method where you can just pass in a list of maps to check
+   * for attribute dependence. Most implementations of
+   * IsAttributeMapped should use this function as a default
+   * handler.
+   */
+  template <size_t N>
+  static bool FindAttributeDependence(
+      const nsAtom* aAttribute, const MappedAttributeEntry* const (&aMaps)[N]) {
+    return FindAttributeDependence(aAttribute, aMaps, N);
+  }
+
+  static nsStaticAtom* const* HTMLSVGPropertiesToTraverseAndUnlink();
+
+  MOZ_CAN_RUN_SCRIPT virtual void HandleInvokeInternal(nsAtom* aAction,
+                                                       ErrorResult& aRv) {}
+
+ private:
+  void DescribeAttribute(uint32_t index, nsAString& aOutDescription) const;
+
+  static bool FindAttributeDependence(const nsAtom* aAttribute,
+                                      const MappedAttributeEntry* const aMaps[],
+                                      uint32_t aMapCount);
+
+ protected:
+  inline bool GetAttr(const nsAtom* aName, DOMString& aResult) const {
+    MOZ_ASSERT(aResult.IsEmpty(), "Should have empty string coming in");
+    const nsAttrValue* val = mAttrs.GetAttr(aName);
+    if (!val) {
+      return false;  // DOMString comes pre-emptied.
+    }
+    val->ToString(aResult);
+    return true;
+  }
+
+  inline bool GetAttr(int32_t aNameSpaceID, const nsAtom* aName,
+                      DOMString& aResult) const {
+    MOZ_ASSERT(aResult.IsEmpty(), "Should have empty string coming in");
+    const nsAttrValue* val = mAttrs.GetAttr(aName, aNameSpaceID);
+    if (!val) {
+      return false;  // DOMString comes pre-emptied.
+    }
+    val->ToString(aResult);
+    return true;
+  }
+
+ public:
+  bool HasAttrs() const { return mAttrs.HasAttrs(); }
+
+  inline bool GetAttr(const nsAString& aName, DOMString& aResult) const {
+    MOZ_ASSERT(aResult.IsEmpty(), "Should have empty string coming in");
+    const nsAttrValue* val = mAttrs.GetAttr(aName);
+    if (val) {
+      val->ToString(aResult);
+      return true;
+    }
+    // else DOMString comes pre-emptied.
+    return false;
+  }
+
+  void GetTagName(nsAString& aTagName) const { aTagName = NodeName(); }
+  void GetId(nsAString& aId) const { GetAttr(nsGkAtoms::id, aId); }
+  void GetId(DOMString& aId) const { GetAttr(nsGkAtoms::id, aId); }
+  void SetId(const nsAString& aId) {
+    SetAttr(kNameSpaceID_None, nsGkAtoms::id, aId, true);
+  }
+  void GetClassName(nsAString& aClassName) {
+    GetAttr(nsGkAtoms::_class, aClassName);
+  }
+  void GetClassName(DOMString& aClassName) {
+    GetAttr(nsGkAtoms::_class, aClassName);
+  }
+  void SetClassName(const nsAString& aClassName) {
+    SetAttr(kNameSpaceID_None, nsGkAtoms::_class, aClassName, true);
+  }
+
+  nsDOMTokenList* ClassList();
+  nsDOMTokenList* Part();
+
+  nsDOMAttributeMap* Attributes();
+
+  void GetAttributeNames(nsTArray<nsString>& aResult);
+
+  void GetAttribute(const nsAString& aName, nsAString& aReturn) {
+    DOMString str;
+    GetAttribute(aName, str);
+    str.ToString(aReturn);
+  }
+
+  void GetAttribute(const nsAString& aName, DOMString& aReturn);
+  void GetAttributeNS(const nsAString& aNamespaceURI,
+                      const nsAString& aLocalName, nsAString& aReturn);
+  bool ToggleAttribute(const nsAString& aName, const Optional<bool>& aForce,
+                       nsIPrincipal* aTriggeringPrincipal, ErrorResult& aError);
+  void SetAttribute(const nsAString& aName, const nsAString& aValue,
+                    nsIPrincipal* aTriggeringPrincipal, ErrorResult& aError);
+  void SetAttributeNS(const nsAString& aNamespaceURI,
+                      const nsAString& aLocalName, const nsAString& aValue,
+                      nsIPrincipal* aTriggeringPrincipal, ErrorResult& aError);
+  void SetAttribute(const nsAString& aName, const nsAString& aValue,
+                    ErrorResult& aError) {
+    SetAttribute(aName, aValue, nullptr, aError);
+  }
+  /**
+   * This method creates a principal that subsumes this element's NodePrincipal
+   * and which has flags set for elevated permissions that devtools needs to
+   * operate on this element. The principal returned by this method is used by
+   * various devtools methods to permit otherwise blocked operations, without
+   * changing any other restrictions the NodePrincipal might have.
+   */
+  already_AddRefed<nsIPrincipal> CreateDevtoolsPrincipal();
+  void SetAttributeDevtools(const nsAString& aName, const nsAString& aValue,
+                            ErrorResult& aError);
+  void SetAttributeDevtoolsNS(const nsAString& aNamespaceURI,
+                              const nsAString& aLocalName,
+                              const nsAString& aValue, ErrorResult& aError);
+
+  void RemoveAttribute(const nsAString& aName, ErrorResult& aError);
+  void RemoveAttributeNS(const nsAString& aNamespaceURI,
+                         const nsAString& aLocalName, ErrorResult& aError);
+  bool HasAttribute(const nsAString& aName) const {
+    return InternalGetAttrNameFromQName(aName) != nullptr;
+  }
+  bool HasAttributeNS(const nsAString& aNamespaceURI,
+                      const nsAString& aLocalName) const;
+  bool HasAttributes() const { return HasAttrs(); }
+  Element* Closest(const nsACString& aSelector, ErrorResult& aResult);
+  bool Matches(const nsACString& aSelector, ErrorResult& aError);
+  already_AddRefed<nsIHTMLCollection> GetElementsByTagName(
+      const nsAString& aQualifiedName);
+  already_AddRefed<nsIHTMLCollection> GetElementsByTagNameNS(
+      const nsAString& aNamespaceURI, const nsAString& aLocalName,
+      ErrorResult& aError);
+  already_AddRefed<nsIHTMLCollection> GetElementsByClassName(
+      const nsAString& aClassNames);
+
+  /**
+   * Returns attribute associated element for the given attribute name, see
+   * https://html.spec.whatwg.org/multipage/common-dom-interfaces.html#attr-associated-element
+   */
+  Element* GetAttrAssociatedElement(nsAtom* aAttr) const;
+
+  /**
+   * Sets an attribute element for the given attribute.
+   * https://html.spec.whatwg.org/multipage/common-dom-interfaces.html#explicitly-set-attr-element
+   */
+  void ExplicitlySetAttrElement(nsAtom* aAttr, Element* aElement);
+
+  void ClearExplicitlySetAttrElement(nsAtom*);
+
+  PseudoStyleType GetPseudoElementType() const {
+    nsresult rv = NS_OK;
+    auto raw = GetProperty(nsGkAtoms::pseudoProperty, &rv);
+    if (rv == NS_PROPTABLE_PROP_NOT_THERE) {
+      return PseudoStyleType::NotPseudo;
+    }
+    return PseudoStyleType(reinterpret_cast<uintptr_t>(raw));
+  }
+
+  void SetPseudoElementType(PseudoStyleType aPseudo) {
+    static_assert(sizeof(PseudoStyleType) <= sizeof(uintptr_t),
+                  "Need to be able to store this in a void*");
+    MOZ_ASSERT(PseudoStyle::IsPseudoElement(aPseudo));
+    SetProperty(nsGkAtoms::pseudoProperty, reinterpret_cast<void*>(aPseudo));
+  }
+
+  /**
+   * Return an array of all elements in the subtree rooted at this
+   * element that have grid container frames. This does not include
+   * pseudo-elements.
+   */
+  void GetElementsWithGrid(nsTArray<RefPtr<Element>>& aElements);
+
+  /**
+   * Provide a direct way to determine if this Element has visible
+   * scrollbars. Flushes layout.
+   */
+  MOZ_CAN_RUN_SCRIPT bool HasVisibleScrollbars();
+
+  /**
+   * Get an editor which handles user inputs when this element has focus.
+   * If this is a text control, return a TextEditor if it's already created.
+   * Otherwise, return nullptr.
+   * If this is not a text control but this is editable, return
+   * HTMLEditor which should've already been created.
+   * Otherwise, return nullptr.
+   */
+  EditorBase* GetEditorWithoutCreation() const;
+
+ private:
+  /**
+   * Implement the algorithm specified at
+   * https://dom.spec.whatwg.org/#insert-adjacent for both
+   * |insertAdjacentElement()| and |insertAdjacentText()| APIs.
+   */
+  nsINode* InsertAdjacent(const nsAString& aWhere, nsINode* aNode,
+                          ErrorResult& aError);
+
+ public:
+  Element* InsertAdjacentElement(const nsAString& aWhere, Element& aElement,
+                                 ErrorResult& aError);
+
+  void InsertAdjacentText(const nsAString& aWhere, const nsAString& aData,
+                          ErrorResult& aError);
+
+  void SetPointerCapture(int32_t aPointerId, ErrorResult& aError);
+  void ReleasePointerCapture(int32_t aPointerId, ErrorResult& aError);
+  bool HasPointerCapture(long aPointerId);
+  void SetCapture(bool aRetargetToElement);
+
+  void SetCaptureAlways(bool aRetargetToElement);
+
+  void ReleaseCapture();
+
+  already_AddRefed<Promise> RequestFullscreen(CallerType, ErrorResult&);
+  void RequestPointerLock(CallerType aCallerType);
+  Attr* GetAttributeNode(const nsAString& aName);
+  already_AddRefed<Attr> SetAttributeNode(Attr& aNewAttr, ErrorResult& aError);
+  already_AddRefed<Attr> RemoveAttributeNode(Attr& aOldAttr,
+                                             ErrorResult& aError);
+  Attr* GetAttributeNodeNS(const nsAString& aNamespaceURI,
+                           const nsAString& aLocalName);
+  already_AddRefed<Attr> SetAttributeNodeNS(Attr& aNewAttr,
+                                            ErrorResult& aError);
+
+  MOZ_CAN_RUN_SCRIPT already_AddRefed<DOMRectList> GetClientRects();
+  MOZ_CAN_RUN_SCRIPT already_AddRefed<DOMRect> GetBoundingClientRect();
+
+  enum class Loading : uint8_t {
+    Eager,
+    Lazy,
+  };
+
+  Loading LoadingState() const;
+  void GetLoading(nsAString& aValue) const;
+  bool ParseLoadingAttribute(const nsAString& aValue, nsAttrValue& aResult);
+
+  // Shadow DOM v1
+  enum class ShadowRootDeclarative : bool { No, Yes };
+
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY
+  already_AddRefed<ShadowRoot> AttachShadow(
+      const ShadowRootInit& aInit, ErrorResult& aError,
+      ShadowRootDeclarative aNewShadowIsDeclarative =
+          ShadowRootDeclarative::No);
+  bool CanAttachShadowDOM() const;
+
+  enum class DelegatesFocus : bool { No, Yes };
+  enum class ShadowRootClonable : bool { No, Yes };
+
+  already_AddRefed<ShadowRoot> AttachShadowWithoutNameChecks(
+      ShadowRootMode aMode, DelegatesFocus = DelegatesFocus::No,
+      SlotAssignmentMode aSlotAssignmentMode = SlotAssignmentMode::Named,
+      ShadowRootClonable aClonable = ShadowRootClonable::No,
+      ShadowRootDeclarative aDeclarative = ShadowRootDeclarative::No);
+
+  // Attach UA Shadow Root if it is not attached.
+  enum class NotifyUAWidgetSetup : bool { No, Yes };
+  void AttachAndSetUAShadowRoot(NotifyUAWidgetSetup = NotifyUAWidgetSetup::Yes,
+                                DelegatesFocus = DelegatesFocus::No);
+
+  // Dispatch an event to UAWidgetsChild, triggering construction
+  // or onchange callback on the existing widget.
+  void NotifyUAWidgetSetupOrChange();
+
+  enum class UnattachShadowRoot {
+    No,
+    Yes,
+  };
+
+  // Dispatch an event to UAWidgetsChild, triggering UA Widget destruction.
+  // and optionally remove the shadow root.
+  void NotifyUAWidgetTeardown(UnattachShadowRoot = UnattachShadowRoot::Yes);
+
+  void UnattachShadow();
+
+  ShadowRoot* GetShadowRootByMode() const;
+  void SetSlot(const nsAString& aName, ErrorResult& aError);
+  void GetSlot(nsAString& aName);
+
+  ShadowRoot* GetShadowRoot() const {
+    const nsExtendedDOMSlots* slots = GetExistingExtendedDOMSlots();
+    return slots ? slots->mShadowRoot.get() : nullptr;
+  }
+
+  const Maybe<float> GetLastRememberedBSize() const {
+    const nsExtendedDOMSlots* slots = GetExistingExtendedDOMSlots();
+    return slots ? slots->mLastRememberedBSize : Nothing();
+  }
+  const Maybe<float> GetLastRememberedISize() const {
+    const nsExtendedDOMSlots* slots = GetExistingExtendedDOMSlots();
+    return slots ? slots->mLastRememberedISize : Nothing();
+  }
+  bool HasLastRememberedBSize() const {
+    return GetLastRememberedBSize().isSome();
+  }
+  bool HasLastRememberedISize() const {
+    return GetLastRememberedISize().isSome();
+  }
+
+  const Maybe<ContentRelevancy> GetContentRelevancy() const {
+    const auto* slots = GetExistingExtendedDOMSlots();
+    return slots ? slots->mContentRelevancy : Nothing();
+  }
+  void SetContentRelevancy(ContentRelevancy relevancy) {
+    ExtendedDOMSlots()->mContentRelevancy = Some(relevancy);
+  }
+
+  const Maybe<bool> GetVisibleForContentVisibility() const {
+    const auto* slots = GetExistingExtendedDOMSlots();
+    return slots ? slots->mVisibleForContentVisibility : Nothing();
+  }
+  void SetVisibleForContentVisibility(bool visible) {
+    ExtendedDOMSlots()->mVisibleForContentVisibility = Some(visible);
+  }
+
+  void ClearContentRelevancy() {
+    if (auto* slots = GetExistingExtendedDOMSlots()) {
+      slots->mContentRelevancy.reset();
+      slots->mVisibleForContentVisibility.reset();
+      slots->mTemporarilyVisibleForScrolledIntoViewDescendant = false;
+    }
+  }
+
+  bool TemporarilyVisibleForScrolledIntoViewDescendant() const {
+    const auto* slots = GetExistingExtendedDOMSlots();
+    return slots && slots->mTemporarilyVisibleForScrolledIntoViewDescendant;
+  }
+
+  void SetTemporarilyVisibleForScrolledIntoViewDescendant(bool aVisible) {
+    ExtendedDOMSlots()->mTemporarilyVisibleForScrolledIntoViewDescendant =
+        aVisible;
+  }
+
+  // https://drafts.csswg.org/cssom-view-1/#dom-element-checkvisibility
+  MOZ_CAN_RUN_SCRIPT bool CheckVisibility(const CheckVisibilityOptions&);
+
+ private:
+  // DO NOT USE THIS FUNCTION directly in C++. This function is supposed to be
+  // called from JS. Use PresShell::ScrollContentIntoView instead.
+  MOZ_CAN_RUN_SCRIPT void ScrollIntoView(const ScrollIntoViewOptions& aOptions);
+
+ public:
+  MOZ_CAN_RUN_SCRIPT
+  // DO NOT USE THIS FUNCTION directly in C++. This function is supposed to be
+  // called from JS. Use PresShell::ScrollContentIntoView instead.
+  void ScrollIntoView(const BooleanOrScrollIntoViewOptions& aObject);
+  MOZ_CAN_RUN_SCRIPT void ScrollTo(double aXScroll, double aYScroll);
+  MOZ_CAN_RUN_SCRIPT void ScrollTo(const ScrollToOptions& aOptions);
+  MOZ_CAN_RUN_SCRIPT void ScrollBy(double aXScrollDif, double aYScrollDif);
+  MOZ_CAN_RUN_SCRIPT void ScrollBy(const ScrollToOptions& aOptions);
+  MOZ_CAN_RUN_SCRIPT int32_t ScrollTop();
+  MOZ_CAN_RUN_SCRIPT void SetScrollTop(int32_t aScrollTop);
+  MOZ_CAN_RUN_SCRIPT int32_t ScrollLeft();
+  MOZ_CAN_RUN_SCRIPT void SetScrollLeft(int32_t aScrollLeft);
+  MOZ_CAN_RUN_SCRIPT int32_t ScrollWidth();
+  MOZ_CAN_RUN_SCRIPT int32_t ScrollHeight();
+  MOZ_CAN_RUN_SCRIPT void MozScrollSnap();
+  MOZ_CAN_RUN_SCRIPT int32_t ClientTop() {
+    return CSSPixel::FromAppUnits(GetClientAreaRect().y).Rounded();
+  }
+  MOZ_CAN_RUN_SCRIPT int32_t ClientLeft() {
+    return CSSPixel::FromAppUnits(GetClientAreaRect().x).Rounded();
+  }
+  MOZ_CAN_RUN_SCRIPT int32_t ClientWidth() {
+    return CSSPixel::FromAppUnits(GetClientAreaRect().Width()).Rounded();
+  }
+  MOZ_CAN_RUN_SCRIPT int32_t ClientHeight() {
+    return CSSPixel::FromAppUnits(GetClientAreaRect().Height()).Rounded();
+  }
+
+  MOZ_CAN_RUN_SCRIPT int32_t ScreenX();
+  MOZ_CAN_RUN_SCRIPT int32_t ScreenY();
+  MOZ_CAN_RUN_SCRIPT already_AddRefed<nsIScreen> GetScreen();
+
+  MOZ_CAN_RUN_SCRIPT int32_t ScrollTopMin();
+  MOZ_CAN_RUN_SCRIPT int32_t ScrollTopMax();
+  MOZ_CAN_RUN_SCRIPT int32_t ScrollLeftMin();
+  MOZ_CAN_RUN_SCRIPT int32_t ScrollLeftMax();
+
+  MOZ_CAN_RUN_SCRIPT double ClientHeightDouble() {
+    return CSSPixel::FromAppUnits(GetClientAreaRect().Height());
+  }
+
+  MOZ_CAN_RUN_SCRIPT double ClientWidthDouble() {
+    return CSSPixel::FromAppUnits(GetClientAreaRect().Width());
+  }
+
+  // This function will return the block size of first line box, no matter if
+  // the box is 'block' or 'inline'. The return unit is pixel. If the element
+  // can't get a primary frame, we will return be zero.
+  double FirstLineBoxBSize() const;
+
+  already_AddRefed<Flex> GetAsFlexContainer();
+  void GetGridFragments(nsTArray<RefPtr<Grid>>& aResult);
+
+  bool HasGridFragments();
+
+  already_AddRefed<DOMMatrixReadOnly> GetTransformToAncestor(
+      Element& aAncestor);
+  already_AddRefed<DOMMatrixReadOnly> GetTransformToParent();
+  already_AddRefed<DOMMatrixReadOnly> GetTransformToViewport();
+
+  already_AddRefed<Animation> Animate(
+      JSContext* aContext, JS::Handle<JSObject*> aKeyframes,
+      const UnrestrictedDoubleOrKeyframeAnimationOptions& aOptions,
+      ErrorResult& aError);
+
+  MOZ_CAN_RUN_SCRIPT
+  void GetAnimations(const GetAnimationsOptions& aOptions,
+                     nsTArray<RefPtr<Animation>>& aAnimations);
+
+  void GetAnimationsWithoutFlush(const GetAnimationsOptions& aOptions,
+                                 nsTArray<RefPtr<Animation>>& aAnimations);
+
+  static void GetAnimationsUnsorted(Element* aElement,
+                                    PseudoStyleType aPseudoType,
+                                    nsTArray<RefPtr<Animation>>& aAnimations);
+
+  void CloneAnimationsFrom(const Element& aOther);
+
+  virtual void GetInnerHTML(nsAString& aInnerHTML, OOMReporter& aError);
+  virtual void SetInnerHTML(const nsAString& aInnerHTML,
+                            nsIPrincipal* aSubjectPrincipal,
+                            ErrorResult& aError);
+  void GetOuterHTML(nsAString& aOuterHTML);
+  void SetOuterHTML(const nsAString& aOuterHTML, ErrorResult& aError);
+  void InsertAdjacentHTML(const nsAString& aPosition, const nsAString& aText,
+                          ErrorResult& aError);
+
+  void SetHTML(const nsAString& aInnerHTML, const SetHTMLOptions& aOptions,
+               ErrorResult& aError);
+
+  //----------------------------------------
+
+  /**
+   * Add a script event listener with the given event handler name
+   * (like onclick) and with the value as JS
+   * @param aEventName the event listener name
+   * @param aValue the JS to attach
+   * @param aDefer indicates if deferred execution is allowed
+   */
+  void SetEventHandler(nsAtom* aEventName, const nsAString& aValue,
+                       bool aDefer = true);
+
+  /**
+   * Do whatever needs to be done when the mouse leaves a link
+   */
+  nsresult LeaveLink(nsPresContext* aPresContext);
+
+  static bool ShouldBlur(nsIContent* aContent);
+
+  /**
+   * Method to create and dispatch a left-click event loosely based on
+   * aSourceEvent. If aFullDispatch is true, the event will be dispatched
+   * through the full dispatching of the presshell of the aPresContext; if it's
+   * false the event will be dispatched only as a DOM event.
+   * If aPresContext is nullptr, this does nothing.
+   *
+   * @param aFlags      Extra flags for the dispatching event.  The true flags
+   *                    will be respected.
+   */
+  MOZ_CAN_RUN_SCRIPT
+  static nsresult DispatchClickEvent(nsPresContext* aPresContext,
+                                     WidgetInputEvent* aSourceEvent,
+                                     nsIContent* aTarget, bool aFullDispatch,
+                                     const EventFlags* aFlags,
+                                     nsEventStatus* aStatus);
+
+  /**
+   * Method to dispatch aEvent to aTarget. If aFullDispatch is true, the event
+   * will be dispatched through the full dispatching of the presshell of the
+   * aPresContext; if it's false the event will be dispatched only as a DOM
+   * event.
+   * If aPresContext is nullptr, this does nothing.
+   */
+  using nsIContent::DispatchEvent;
+  MOZ_CAN_RUN_SCRIPT
+  static nsresult DispatchEvent(nsPresContext* aPresContext,
+                                WidgetEvent* aEvent, nsIContent* aTarget,
+                                bool aFullDispatch, nsEventStatus* aStatus);
+
+  bool IsDisplayContents() const {
+    return HasServoData() && Servo_Element_IsDisplayContents(this);
+  }
+
+  /*
+   * https://html.spec.whatwg.org/#being-rendered
+   *
+   * With a gotcha for display contents:
+   *   https://github.com/whatwg/html/issues/1837
+   */
+  bool IsRendered() const { return GetPrimaryFrame() || IsDisplayContents(); }
+
+  const nsAttrValue* GetParsedAttr(const nsAtom* aAttr) const {
+    return mAttrs.GetAttr(aAttr);
+  }
+
+  const nsAttrValue* GetParsedAttr(const nsAtom* aAttr,
+                                   int32_t aNameSpaceID) const {
+    return mAttrs.GetAttr(aAttr, aNameSpaceID);
+  }
+
+  /**
+   * Returns the attribute map, if there is one.
+   *
+   * @return existing attribute map or nullptr.
+   */
+  nsDOMAttributeMap* GetAttributeMap() {
+    nsDOMSlots* slots = GetExistingDOMSlots();
+
+    return slots ? slots->mAttributeMap.get() : nullptr;
+  }
+
+  void RecompileScriptEventListeners();
+
+  /**
+   * Get the attr info for the given namespace ID and attribute name.  The
+   * namespace ID must not be kNameSpaceID_Unknown and the name must not be
+   * null.  Note that this can only return info on attributes that actually
+   * live on this element (and is only virtual to handle XUL prototypes).  That
+   * is, this should only be called from methods that only care about attrs
+   * that effectively live in mAttrs.
+   */
+  BorrowedAttrInfo GetAttrInfo(int32_t aNamespaceID,
+                               const nsAtom* aName) const {
+    NS_ASSERTION(aName, "must have attribute name");
+    NS_ASSERTION(aNamespaceID != kNameSpaceID_Unknown,
+                 "must have a real namespace ID!");
+
+    int32_t index = mAttrs.IndexOfAttr(aName, aNamespaceID);
+    if (index < 0) {
+      return BorrowedAttrInfo(nullptr, nullptr);
+    }
+
+    return mAttrs.AttrInfoAt(index);
+  }
+
+  /**
+   * Parse a string into an nsAttrValue for a CORS attribute.  This
+   * never fails.  The resulting value is an enumerated value whose
+   * GetEnumValue() returns one of the above constants.
+   */
+  static void ParseCORSValue(const nsAString& aValue, nsAttrValue& aResult);
+
+  /**
+   * Return the CORS mode for a given string
+   */
+  static CORSMode StringToCORSMode(const nsAString& aValue);
+
+  /**
+   * Return the CORS mode for a given nsAttrValue (which may be null,
+   * but if not should have been parsed via ParseCORSValue).
+   */
+  static CORSMode AttrValueToCORSMode(const nsAttrValue* aValue);
+
+  nsINode* GetScopeChainParent() const override;
+
+  /**
+   * Locate a TextEditor rooted at this content node, if there is one.
+   */
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY mozilla::TextEditor* GetTextEditorInternal();
+
+  /**
+   * Gets value of boolean attribute. Only works for attributes in null
+   * namespace.
+   *
+   * @param aAttr    name of attribute.
+   * @param aValue   Boolean value of attribute.
+   */
+  bool GetBoolAttr(nsAtom* aAttr) const { return HasAttr(aAttr); }
+
+  /**
+   * Sets value of boolean attribute by removing attribute or setting it to
+   * the empty string. Only works for attributes in null namespace.
+   *
+   * @param aAttr    name of attribute.
+   * @param aValue   Boolean value of attribute.
+   */
+  nsresult SetBoolAttr(nsAtom* aAttr, bool aValue);
+
+  /**
+   * Gets the enum value string of an attribute and using a default value if
+   * the attribute is missing or the string is an invalid enum value.
+   *
+   * @param aType     the name of the attribute.
+   * @param aDefault  the default value if the attribute is missing or invalid.
+   * @param aResult   string corresponding to the value [out].
+   */
+  void GetEnumAttr(nsAtom* aAttr, const char* aDefault,
+                   nsAString& aResult) const;
+
+  /**
+   * Gets the enum value string of an attribute and using the default missing
+   * value if the attribute is missing or the default invalid value if the
+   * string is an invalid enum value.
+   *
+   * @param aType            the name of the attribute.
+   * @param aDefaultMissing  the default value if the attribute is missing.  If
+                             null and the attribute is missing, aResult will be
+                             set to the null DOMString; this only matters for
+                             cases in which we're reflecting a nullable string.
+   * @param aDefaultInvalid  the default value if the attribute is invalid.
+   * @param aResult          string corresponding to the value [out].
+   */
+  void GetEnumAttr(nsAtom* aAttr, const char* aDefaultMissing,
+                   const char* aDefaultInvalid, nsAString& aResult) const;
+
+  /**
+   * Unset an attribute.
+   */
+  void UnsetAttr(nsAtom* aAttr, ErrorResult& aError) {
+    aError = UnsetAttr(kNameSpaceID_None, aAttr, true);
+  }
+
+  /**
+   * Set an attribute in the simplest way possible.
+   */
+  void SetAttr(nsAtom* aAttr, const nsAString& aValue, ErrorResult& aError) {
+    aError = SetAttr(kNameSpaceID_None, aAttr, aValue, true);
+  }
+
+  void SetAttr(nsAtom* aAttr, const nsAString& aValue,
+               nsIPrincipal* aTriggeringPrincipal, ErrorResult& aError) {
+    aError =
+        SetAttr(kNameSpaceID_None, aAttr, aValue, aTriggeringPrincipal, true);
+  }
+
+  /**
+   * Preallocate space in this element's attribute array for the given
+   * total number of attributes.
+   */
+  void TryReserveAttributeCount(uint32_t aAttributeCount);
+
+  void SetParserHadDuplicateAttributeError() {
+    SetFlags(ELEMENT_PARSER_HAD_DUPLICATE_ATTR_ERROR);
+  }
+
+  /**
+   * Set a content attribute via a reflecting nullable string IDL
+   * attribute (e.g. a CORS attribute).  If DOMStringIsNull(aValue),
+   * this will actually remove the content attribute.
+   */
+  void SetOrRemoveNullableStringAttr(nsAtom* aName, const nsAString& aValue,
+                                     ErrorResult& aError);
+
+  /**
+   * Retrieve the ratio of font-size-inflated text font size to computed font
+   * size for this element. This will query the element for its primary frame,
+   * and then use this to get font size inflation information about the frame.
+   *
+   * @returns The font size inflation ratio (inflated font size to uninflated
+   *          font size) for the primary frame of this element. Returns 1.0
+   *          by default if font size inflation is not enabled. Returns -1
+   *          if the element does not have a primary frame.
+   *
+   * @note The font size inflation ratio that is returned is actually the
+   *       font size inflation data for the element's _primary frame_, not the
+   *       element itself, but for most purposes, this should be sufficient.
+   */
+  float FontSizeInflation();
+
+  void GetImplementedPseudoElement(nsAString&) const;
+
+  ReferrerPolicy GetReferrerPolicyAsEnum() const;
+  ReferrerPolicy ReferrerPolicyFromAttr(const nsAttrValue* aValue) const;
+
+  /*
+   * Helpers for .dataset.  This is implemented on Element, though only some
+   * sorts of elements expose it to JS as a .dataset property
+   */
+  // Getter, to be called from bindings.
+  already_AddRefed<nsDOMStringMap> Dataset();
+  // Callback for destructor of dataset to ensure to null out our weak pointer
+  // to it.
+  void ClearDataset();
+
+  void RegisterIntersectionObserver(DOMIntersectionObserver* aObserver);
+  void UnregisterIntersectionObserver(DOMIntersectionObserver* aObserver);
+  void UnlinkIntersectionObservers();
+  bool UpdateIntersectionObservation(DOMIntersectionObserver* aObserver,
+                                     int32_t threshold);
+
+  // A number of methods to cast to various XUL interfaces. They return a
+  // pointer only if the element implements that interface.
+  already_AddRefed<nsIDOMXULButtonElement> AsXULButton();
+  already_AddRefed<nsIDOMXULContainerElement> AsXULContainer();
+  already_AddRefed<nsIDOMXULContainerItemElement> AsXULContainerItem();
+  already_AddRefed<nsIDOMXULControlElement> AsXULControl();
+  already_AddRefed<nsIDOMXULMenuListElement> AsXULMenuList();
+  already_AddRefed<nsIDOMXULMultiSelectControlElement>
+  AsXULMultiSelectControl();
+  already_AddRefed<nsIDOMXULRadioGroupElement> AsXULRadioGroup();
+  already_AddRefed<nsIDOMXULRelatedElement> AsXULRelated();
+  already_AddRefed<nsIDOMXULSelectControlElement> AsXULSelectControl();
+  already_AddRefed<nsIDOMXULSelectControlItemElement> AsXULSelectControlItem();
+  already_AddRefed<nsIBrowser> AsBrowser();
+  already_AddRefed<nsIAutoCompletePopup> AsAutoCompletePopup();
+
+  /**
+   * Get the presentation context for this content node.
+   * @return the presentation context
+   */
+  enum PresContextFor { eForComposedDoc, eForUncomposedDoc };
+  nsPresContext* GetPresContext(PresContextFor aFor);
+
+  /**
+   * The method focuses (or activates) element that accesskey is bound to. It is
+   * called when accesskey is activated.
+   *
+   * @param aKeyCausesActivation - if true then element should be activated
+   * @param aIsTrustedEvent - if true then event that is cause of accesskey
+   *                          execution is trusted.
+   * @return an error if the element isn't able to handle the accesskey (caller
+   *         would look for the next element to handle it).
+   *         a boolean indicates whether the focus moves to the element after
+   *         the element handles the accesskey.
+   */
+  MOZ_CAN_RUN_SCRIPT
+  virtual Result<bool, nsresult> PerformAccesskey(bool aKeyCausesActivation,
+                                                  bool aIsTrustedEvent) {
+    return Err(NS_ERROR_NOT_IMPLEMENTED);
+  }
+
+ protected:
+  // Supported rel values for <form> and anchors.
+  static const DOMTokenListSupportedToken sAnchorAndFormRelValues[];
+
+  /*
+   * Named-bools for use with SetAttrAndNotify to make call sites easier to
+   * read.
+   */
+  static const bool kFireMutationEvent = true;
+  static const bool kDontFireMutationEvent = false;
+  static const bool kNotifyDocumentObservers = true;
+  static const bool kDontNotifyDocumentObservers = false;
+  static const bool kCallAfterSetAttr = true;
+  static const bool kDontCallAfterSetAttr = false;
+
+  /*
+   * The supported values of blocking attribute for use with nsDOMTokenList.
+   */
+  static const DOMTokenListSupportedToken sSupportedBlockingValues[];
+
+  /**
+   * Set attribute and (if needed) notify documentobservers and fire off
+   * mutation events.  This will send the AttributeChanged notification.
+   * Callers of this method are responsible for calling AttributeWillChange,
+   * since that needs to happen before the new attr value has been set, and
+   * in particular before it has been parsed.
+   *
+   * For the boolean parameters, consider using the named bools above to aid
+   * code readability.
+   *
+   * @param aNamespaceID  namespace of attribute
+   * @param aAttribute    local-name of attribute
+   * @param aPrefix       aPrefix of attribute
+   * @param aOldValue     The old value of the attribute to use as a fallback
+   *                      in the cases where the actual old value (i.e.
+   *                      its current value) is !StoresOwnData() --- in which
+   *                      case the current value is probably already useless.
+   *                      If the current value is StoresOwnData() (or absent),
+   *                      aOldValue will not be used. aOldValue will only be set
+   *                      in certain circumstances (there are mutation
+   *                      listeners, element is a custom element, attribute was
+   *                      not previously unset). Otherwise it will be null.
+   * @param aParsedValue  parsed new value of attribute. Replaced by the
+   *                      old value of the attribute. This old value is only
+   *                      useful if either it or the new value is StoresOwnData.
+   * @param aSubjectPrincipal
+   *                      the principal of the scripted caller responsible for
+   *                      setting the attribute, or null if no scripted caller
+   *                      can be determined. A null value here does not
+   *                      guarantee that there is no scripted caller, but a
+   *                      non-null value does guarantee that a scripted caller
+   *                      with the given principal is directly responsible for
+   *                      the attribute change.
+   * @param aModType      MutationEvent_Binding::MODIFICATION or ADDITION.  Only
+   *                      needed if aFireMutation or aNotify is true.
+   * @param aFireMutation should mutation-events be fired?
+   * @param aNotify       should we notify document-observers?
+   * @param aCallAfterSetAttr should we call AfterSetAttr?
+   * @param aComposedDocument The current composed document of the element.
+   * @param aGuard        For making sure that this is called with a
+   *                      mozAutoDocUpdate instance, this is here.  Specify
+   *                      an instance of it which you created for the call.
+   */
+  nsresult SetAttrAndNotify(int32_t aNamespaceID, nsAtom* aName,
+                            nsAtom* aPrefix, const nsAttrValue* aOldValue,
+                            nsAttrValue& aParsedValue,
+                            nsIPrincipal* aSubjectPrincipal, uint8_t aModType,
+                            bool aFireMutation, bool aNotify,
+                            bool aCallAfterSetAttr, Document* aComposedDocument,
+                            const mozAutoDocUpdate& aGuard);
+
+  /**
+   * Convert an attribute string value to attribute type based on the type of
+   * attribute.  Called by SetAttr().  Note that at the moment we only do this
+   * for attributes in the null namespace (kNameSpaceID_None).
+   *
+   * @param aNamespaceID the namespace of the attribute to convert
+   * @param aAttribute the attribute to convert
+   * @param aValue the string value to convert
+   * @param aMaybeScriptedPrincipal the principal of the script setting the
+   *        attribute, if one can be determined, or null otherwise. As in
+   *        AfterSetAttr, a null value does not guarantee that the attribute was
+   *        not set by a scripted caller, but a non-null value guarantees that
+   *        the attribute was set by a scripted caller with the given principal.
+   * @param aResult the nsAttrValue [OUT]
+   * @return true if the parsing was successful, false otherwise
+   */
+  virtual bool ParseAttribute(int32_t aNamespaceID, nsAtom* aAttribute,
+                              const nsAString& aValue,
+                              nsIPrincipal* aMaybeScriptedPrincipal,
+                              nsAttrValue& aResult);
+
+  /**
+   * Hook that is called by Element::SetAttr to allow subclasses to
+   * deal with attribute sets.  This will only be called after we verify that
+   * we're actually doing an attr set and will be called before
+   * AttributeWillChange and before ParseAttribute and hence before we've set
+   * the new value.
+   *
+   * @param aNamespaceID the namespace of the attr being set
+   * @param aName the localname of the attribute being set
+   * @param aValue the value it's being set to represented as either a string or
+   *        a parsed nsAttrValue. Alternatively, if the attr is being removed it
+   *        will be null.
+   * @param aNotify Whether we plan to notify document observers.
+   */
+  virtual void BeforeSetAttr(int32_t aNamespaceID, nsAtom* aName,
+                             const nsAttrValue* aValue, bool aNotify);
+
+  /**
+   * Hook that is called by Element::SetAttr to allow subclasses to
+   * deal with attribute sets.  This will only be called after we have called
+   * SetAndSwapAttr (that is, after we have actually set the attr).  It will
+   * always be called under a scriptblocker.
+   *
+   * @param aNamespaceID the namespace of the attr being set
+   * @param aName the localname of the attribute being set
+   * @param aValue the value it's being set to.  If null, the attr is being
+   *        removed.
+   * @param aOldValue the value that the attribute had previously. If null,
+   *        the attr was not previously set. This argument may not have the
+   *        correct value for SVG elements, or other cases in which the
+   *        attribute value doesn't store its own data
+   * @param aMaybeScriptedPrincipal the principal of the scripted caller
+   *        responsible for setting the attribute, or null if no scripted caller
+   *        can be determined, or the attribute is being unset. A null value
+   *        here does not guarantee that there is no scripted caller, but a
+   *        non-null value does guarantee that a scripted caller with the given
+   *        principal is directly responsible for the attribute change.
+   * @param aNotify Whether we plan to notify document observers.
+   */
+  virtual void AfterSetAttr(int32_t aNamespaceID, nsAtom* aName,
+                            const nsAttrValue* aValue,
+                            const nsAttrValue* aOldValue,
+                            nsIPrincipal* aMaybeScriptedPrincipal,
+                            bool aNotify);
+
+  /**
+   * This function shall be called just before the id attribute changes. It will
+   * be called after BeforeSetAttr. If the attribute being changed is not the id
+   * attribute, this function does nothing. Otherwise, it will remove the old id
+   * from the document's id cache.
+   *
+   * This must happen after BeforeSetAttr (rather than during) because the
+   * the subclasses' calls to BeforeSetAttr may notify on state changes. If they
+   * incorrectly determine whether the element had an id, the element may not be
+   * restyled properly.
+   *
+   * @param aNamespaceID the namespace of the attr being set
+   * @param aName the localname of the attribute being set
+   * @param aValue the new id value. Will be null if the id is being unset.
+   */
+  void PreIdMaybeChange(int32_t aNamespaceID, nsAtom* aName,
+                        const nsAttrValue* aValue);
+
+  /**
+   * This function shall be called just after the id attribute changes. It will
+   * be called before AfterSetAttr. If the attribute being changed is not the id
+   * attribute, this function does nothing. Otherwise, it will add the new id to
+   * the document's id cache and properly set the ElementHasID flag.
+   *
+   * This must happen before AfterSetAttr (rather than during) because the
+   * the subclasses' calls to AfterSetAttr may notify on state changes. If they
+   * incorrectly determine whether the element now has an id, the element may
+   * not be restyled properly.
+   *
+   * @param aNamespaceID the namespace of the attr being set
+   * @param aName the localname of the attribute being set
+   * @param aValue the new id value. Will be null if the id is being unset.
+   */
+  void PostIdMaybeChange(int32_t aNamespaceID, nsAtom* aName,
+                         const nsAttrValue* aValue);
+
+  /**
+   * Usually, setting an attribute to the value that it already has results in
+   * no action. However, in some cases, setting an attribute to its current
+   * value should have the effect of, for example, forcing a reload of
+   * network data. To address that, this function will be called in this
+   * situation to allow the handling of such a case.
+   *
+   * @param aNamespaceID the namespace of the attr being set
+   * @param aName the localname of the attribute being set
+   * @param aValue the value it's being set to represented as either a string or
+   *        a parsed nsAttrValue.
+   * @param aNotify Whether we plan to notify document observers.
+   */
+  virtual void OnAttrSetButNotChanged(int32_t aNamespaceID, nsAtom* aName,
+                                      const nsAttrValueOrString& aValue,
+                                      bool aNotify);
+
+  /**
+   * Hook to allow subclasses to produce a different EventListenerManager if
+   * needed for attachment of attribute-defined handlers
+   */
+  virtual EventListenerManager* GetEventListenerManagerForAttr(
+      nsAtom* aAttrName, bool* aDefer);
+
+  /**
+   * Internal hook for converting an attribute name-string to nsAttrName in
+   * case there is such existing attribute. aNameToUse can be passed to get
+   * name which was used for looking for the attribute (lowercase in HTML).
+   */
+  const nsAttrName* InternalGetAttrNameFromQName(
+      const nsAString& aStr, nsAutoString* aNameToUse = nullptr) const;
+
+  virtual Element* GetNameSpaceElement() override { return this; }
+
+  Attr* GetAttributeNodeNSInternal(const nsAString& aNamespaceURI,
+                                   const nsAString& aLocalName);
+
+  inline void RegisterActivityObserver();
+  inline void UnregisterActivityObserver();
+
+  /**
+   * Add/remove this element to the documents id cache
+   */
+  void AddToIdTable(nsAtom* aId);
+  void RemoveFromIdTable();
+
+  /**
+   * Functions to carry out event default actions for links of all types
+   * (HTML links, XLinks, SVG "XLinks", etc.)
+   */
+
+  /**
+   * Check that we meet the conditions to handle a link event
+   * and that we are actually on a link.
+   *
+   * @param aVisitor event visitor
+   * @return true if we can handle the link event, false otherwise
+   */
+  bool CheckHandleEventForLinksPrecondition(EventChainVisitor& aVisitor) const;
+
+  /**
+   * Handle status bar updates before they can be cancelled.
+   */
+  void GetEventTargetParentForLinks(EventChainPreVisitor& aVisitor);
+
+  void DispatchChromeOnlyLinkClickEvent(EventChainPostVisitor& aVisitor);
+
+  /**
+   * Handle default actions for link event if the event isn't consumed yet.
+   */
+  MOZ_CAN_RUN_SCRIPT
+  nsresult PostHandleEventForLinks(EventChainPostVisitor& aVisitor);
+
+ public:
+  /**
+   * Check if this element is a link. This matches the CSS definition of the
+   * :any-link pseudo-class.
+   */
+  bool IsLink() const {
+    return mState.HasAtLeastOneOfStates(ElementState::VISITED |
+                                        ElementState::UNVISITED);
+  }
+
+  /**
+   * Get a pointer to the full href URI (fully resolved and canonicalized, since
+   * it's an nsIURI object) for link elements.
+   *
+   * @return A pointer to the URI or null if the element is not a link, or it
+   *         has no HREF attribute, or the HREF attribute is an invalid URI.
+   */
+  virtual already_AddRefed<nsIURI> GetHrefURI() const { return nullptr; }
+
+  /**
+   * Get the target of this link element. Consumers should established that
+   * this element is a link (probably using IsLink) before calling this
+   * function (or else why call it?)
+   *
+   * Note: for HTML this gets the value of the 'target' attribute; for XLink
+   * this gets the value of the xlink:_moz_target attribute, or failing that,
+   * the value of xlink:show, converted to a suitably equivalent named target
+   * (e.g. _blank).
+   */
+  virtual void GetLinkTarget(nsAString& aTarget);
+
+  virtual bool Translate() const;
+
+  MOZ_CAN_RUN_SCRIPT
+  virtual void SetHTMLUnsafe(const nsAString& aHTML);
+
+ protected:
+  enum class ReparseAttributes { No, Yes };
+  /**
+   * Copy attributes and state to another element
+   * @param aDest the object to copy to
+   */
+  nsresult CopyInnerTo(Element* aDest,
+                       ReparseAttributes = ReparseAttributes::Yes);
+
+  /**
+   * Some event handler content attributes have a different name (e.g. different
+   * case) from the actual event name.  This function takes an event handler
+   * content attribute name and returns the corresponding event name, to be used
+   * for adding the actual event listener.
+   */
+  virtual nsAtom* GetEventNameForAttr(nsAtom* aAttr);
+
+  /**
+   * Register/unregister this element to accesskey map if it supports accesskey.
+   */
+  virtual void RegUnRegAccessKey(bool aDoReg);
+
+ private:
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+  void AssertInvariantsOnNodeInfoChange();
+#endif
+
+  /**
+   * Slow path for GetClasses, this should only be called for SVG elements.
+   */
+  const nsAttrValue* GetSVGAnimatedClass() const;
+
+  /**
+   * Get this element's client area rect in app units.
+   * @return the frame's client area
+   */
+  MOZ_CAN_RUN_SCRIPT nsRect GetClientAreaRect();
+
+  /** Gets the scroll size as for the scroll{Width,Height} APIs */
+  MOZ_CAN_RUN_SCRIPT nsSize GetScrollSize();
+  /** Gets the scroll position as for the scroll{Top,Left} APIs */
+  MOZ_CAN_RUN_SCRIPT nsPoint GetScrollOrigin();
+  /** Gets the scroll range as for the scroll{Top,Left}{Min,Max} APIs */
+  MOZ_CAN_RUN_SCRIPT nsRect GetScrollRange();
+
+  /**
+   * GetCustomInterface is somewhat like a GetInterface, but it is expected
+   * that the implementation is provided by a custom element or via the
+   * the XBL implements keyword. To use this, create a public method that
+   * wraps a call to GetCustomInterface.
+   */
+  template <class T>
+  void GetCustomInterface(nsGetterAddRefs<T> aResult);
+
+  // Prevent people from doing pointless checks/casts on Element instances.
+  void IsElement() = delete;
+  void AsElement() = delete;
+
+  // Data members
+  ElementState mState;
+  // Per-node data managed by Servo.
+  //
+  // There should not be data on nodes that are not in the flattened tree, or
+  // descendants of display: none elements.
+  mozilla::RustCell<ServoNodeData*> mServoData;
+
+ protected:
+  // Array containing all attributes for this element
+  AttrArray mAttrs;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(Element, NS_ELEMENT_IID)
+
+inline bool Element::HasNonEmptyAttr(int32_t aNameSpaceID,
+                                     const nsAtom* aName) const {
+  MOZ_ASSERT(aNameSpaceID > kNameSpaceID_Unknown, "Must have namespace");
+  MOZ_ASSERT(aName, "Must have attribute name");
+
+  const nsAttrValue* val = mAttrs.GetAttr(aName, aNameSpaceID);
+  return val && !val->IsEmptyString();
+}
+
+inline bool Element::AttrValueIs(int32_t aNameSpaceID, const nsAtom* aName,
+                                 const nsAString& aValue,
+                                 nsCaseTreatment aCaseSensitive) const {
+  return mAttrs.AttrValueIs(aNameSpaceID, aName, aValue, aCaseSensitive);
+}
+
+inline bool Element::AttrValueIs(int32_t aNameSpaceID, const nsAtom* aName,
+                                 const nsAtom* aValue,
+                                 nsCaseTreatment aCaseSensitive) const {
+  return mAttrs.AttrValueIs(aNameSpaceID, aName, aValue, aCaseSensitive);
+}
+
+}  // namespace dom
+}  // namespace mozilla
+
+NON_VIRTUAL_ADDREF_RELEASE(mozilla::dom::Element)
+
+inline mozilla::dom::Element* nsINode::AsElement() {
+  MOZ_ASSERT(IsElement());
+  return static_cast<mozilla::dom::Element*>(this);
+}
+
+inline const mozilla::dom::Element* nsINode::AsElement() const {
+  MOZ_ASSERT(IsElement());
+  return static_cast<const mozilla::dom::Element*>(this);
+}
+
+inline mozilla::dom::Element* nsINode::GetParentElement() const {
+  return mozilla::dom::Element::FromNodeOrNull(mParent);
+}
+
+inline mozilla::dom::Element* nsINode::GetPreviousElementSibling() const {
+  nsIContent* previousSibling = GetPreviousSibling();
+  while (previousSibling) {
+    if (previousSibling->IsElement()) {
+      return previousSibling->AsElement();
+    }
+    previousSibling = previousSibling->GetPreviousSibling();
+  }
+
+  return nullptr;
+}
+
+inline mozilla::dom::Element* nsINode::GetAsElementOrParentElement() const {
+  return IsElement() ? const_cast<mozilla::dom::Element*>(AsElement())
+                     : GetParentElement();
+}
+
+inline mozilla::dom::Element* nsINode::GetNextElementSibling() const {
+  nsIContent* nextSibling = GetNextSibling();
+  while (nextSibling) {
+    if (nextSibling->IsElement()) {
+      return nextSibling->AsElement();
+    }
+    nextSibling = nextSibling->GetNextSibling();
+  }
+
+  return nullptr;
+}
+
+/**
+ * Macros to implement Clone(). _elementName is the class for which to implement
+ * Clone.
+ */
+#define NS_IMPL_ELEMENT_CLONE(_elementName)                         \
+  nsresult _elementName::Clone(mozilla::dom::NodeInfo* aNodeInfo,   \
+                               nsINode** aResult) const {           \
+    *aResult = nullptr;                                             \
+    RefPtr<mozilla::dom::NodeInfo> ni(aNodeInfo);                   \
+    auto* nim = ni->NodeInfoManager();                              \
+    RefPtr<_elementName> it = new (nim) _elementName(ni.forget());  \
+    nsresult rv = const_cast<_elementName*>(this)->CopyInnerTo(it); \
+    if (NS_SUCCEEDED(rv)) {                                         \
+      it.forget(aResult);                                           \
+    }                                                               \
+                                                                    \
+    return rv;                                                      \
+  }
+
+#define EXPAND(...) __VA_ARGS__
+#define NS_IMPL_ELEMENT_CLONE_WITH_INIT_HELPER(_elementName, extra_args_) \
+  nsresult _elementName::Clone(mozilla::dom::NodeInfo* aNodeInfo,         \
+                               nsINode** aResult) const {                 \
+    *aResult = nullptr;                                                   \
+    RefPtr<mozilla::dom::NodeInfo> ni(aNodeInfo);                         \
+    auto* nim = ni->NodeInfoManager();                                    \
+    RefPtr<_elementName> it =                                             \
+        new (nim) _elementName(ni.forget() EXPAND extra_args_);           \
+    nsresult rv = it->Init();                                             \
+    nsresult rv2 = const_cast<_elementName*>(this)->CopyInnerTo(it);      \
+    if (NS_FAILED(rv2)) {                                                 \
+      rv = rv2;                                                           \
+    }                                                                     \
+    if (NS_SUCCEEDED(rv)) {                                               \
+      it.forget(aResult);                                                 \
+    }                                                                     \
+                                                                          \
+    return rv;                                                            \
+  }
+
+#define NS_IMPL_ELEMENT_CLONE_WITH_INIT(_elementName) \
+  NS_IMPL_ELEMENT_CLONE_WITH_INIT_HELPER(_elementName, ())
+#define NS_IMPL_ELEMENT_CLONE_WITH_INIT_AND_PARSER(_elementName) \
+  NS_IMPL_ELEMENT_CLONE_WITH_INIT_HELPER(_elementName, (, NOT_FROM_PARSER))
+
+#endif  // mozilla_dom_Element_h__