Adding upstream version 110.0.1.upstream/110.0.1upstream

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

1 files changed, 652 insertions, 0 deletions

diff --git a/layout/style/ServoStyleSet.h b/layout/style/ServoStyleSet.h
new file mode 100644
index 0000000000..fb051002c8
--- /dev/null
+++ b/layout/style/ServoStyleSet.h
@@ -0,0 +1,652 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ServoStyleSet_h
+#define mozilla_ServoStyleSet_h
+
+#include "mozilla/AnonymousContentKey.h"
+#include "mozilla/AtomArray.h"
+#include "mozilla/EnumeratedArray.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/PostTraversalTask.h"
+#include "mozilla/ServoBindingTypes.h"
+#include "mozilla/ServoUtils.h"
+#include "mozilla/dom/RustTypes.h"
+#include "mozilla/UniquePtr.h"
+#include "MainThreadUtils.h"
+#include "nsCSSPseudoElements.h"
+#include "nsCSSAnonBoxes.h"
+#include "nsChangeHint.h"
+#include "nsCoord.h"
+#include "nsAtom.h"
+#include "nsIMemoryReporter.h"
+#include "nsTArray.h"
+#include "nsIMemoryReporter.h"
+
+namespace mozilla {
+enum class MediaFeatureChangeReason : uint16_t;
+enum class StylePageSizeOrientation : uint8_t;
+enum class StyleRuleChangeKind : uint32_t;
+
+template <typename Integer, typename Number, typename LinearStops>
+struct StyleTimingFunction;
+struct StylePiecewiseLinearFunction;
+using StyleComputedTimingFunction =
+    StyleTimingFunction<int32_t, float, StylePiecewiseLinearFunction>;
+
+namespace css {
+class Rule;
+}  // namespace css
+namespace dom {
+class CSSImportRule;
+class Element;
+class ShadowRoot;
+}  // namespace dom
+namespace gfx {
+class FontPaletteValueSet;
+}  // namespace gfx
+class StyleSheet;
+struct Keyframe;
+class ServoElementSnapshotTable;
+class ComputedStyle;
+class ServoStyleRuleMap;
+class StyleSheet;
+}  // namespace mozilla
+class gfxFontFeatureValueSet;
+class nsIContent;
+
+class nsPresContext;
+class nsWindowSizes;
+struct TreeMatchContext;
+
+namespace mozilla {
+
+// A few flags used to track which kind of stylist state we may need to
+// update.
+enum class StylistState : uint8_t {
+  // The stylist is not dirty, we should do nothing.
+  NotDirty = 0,
+
+  // The style sheets have changed, so we need to update the style data.
+  StyleSheetsDirty = 1 << 0,
+
+  // Some of the style sheets of the shadow trees in the document have
+  // changed.
+  ShadowDOMStyleSheetsDirty = 1 << 1,
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(StylistState)
+
+enum class StyleOrigin : uint8_t;
+
+// Bitfield type to represent Servo stylesheet origins.
+enum class OriginFlags : uint8_t {
+  UserAgent = 0x01,
+  User = 0x02,
+  Author = 0x04,
+  All = 0x07,
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(OriginFlags)
+
+/**
+ * The set of style sheets that apply to a document, backed by a Servo
+ * Stylist.  A ServoStyleSet contains StyleSheets.
+ */
+class ServoStyleSet {
+  friend class RestyleManager;
+  using SnapshotTable = ServoElementSnapshotTable;
+  using Origin = StyleOrigin;
+
+  // We assert that these match the Servo ones in the definition of this array.
+  static constexpr Origin kOrigins[] = {
+      Origin(static_cast<uint8_t>(OriginFlags::UserAgent)),
+      Origin(static_cast<uint8_t>(OriginFlags::User)),
+      Origin(static_cast<uint8_t>(OriginFlags::Author)),
+  };
+
+ public:
+  static bool IsInServoTraversal() { return mozilla::IsInServoTraversal(); }
+
+#ifdef DEBUG
+  // Used for debug assertions. We make this debug-only to prevent callers from
+  // accidentally using it instead of IsInServoTraversal, which is cheaper. We
+  // can change this if a use-case arises.
+  static bool IsCurrentThreadInServoTraversal();
+#endif
+
+  static ServoStyleSet* Current() { return sInServoTraversal; }
+
+  explicit ServoStyleSet(dom::Document&);
+  ~ServoStyleSet();
+
+  void ShellDetachedFromDocument();
+
+  // Called when a rules in a stylesheet in this set, or a child sheet of that,
+  // are mutated from CSSOM.
+  void RuleAdded(StyleSheet&, css::Rule&);
+  void RuleRemoved(StyleSheet&, css::Rule&);
+  void RuleChanged(StyleSheet&, css::Rule*, StyleRuleChangeKind);
+  void SheetCloned(StyleSheet&);
+  void ImportRuleLoaded(dom::CSSImportRule&, StyleSheet&);
+
+  // Runs style invalidation due to document state changes.
+  void InvalidateStyleForDocumentStateChanges(
+      dom::DocumentState aStatesChanged);
+
+  void RecordShadowStyleChange(dom::ShadowRoot&);
+
+  bool StyleSheetsHaveChanged() const { return StylistNeedsUpdate(); }
+
+  RestyleHint MediumFeaturesChanged(MediaFeatureChangeReason);
+
+  // Evaluates a given SourceSizeList, returning the optimal viewport width in
+  // app units.
+  //
+  // The SourceSizeList parameter can be null, in which case it will return
+  // 100vw.
+  inline nscoord EvaluateSourceSizeList(
+      const RawServoSourceSizeList* aSourceSizeList) const;
+
+  void AddSizeOfIncludingThis(nsWindowSizes& aSizes) const;
+  const RawServoStyleSet* RawSet() const { return mRawSet.get(); }
+
+  bool GetAuthorStyleDisabled() const { return mAuthorStyleDisabled; }
+
+  bool UsesFontMetrics() const;
+
+  void SetAuthorStyleDisabled(bool aStyleDisabled);
+
+  // Get a CopmutedStyle for a text node (which no rules will match).
+  //
+  // The returned ComputedStyle will have nsCSSAnonBoxes::mozText() as its
+  // pseudo.
+  //
+  // (Perhaps mozText should go away and we shouldn't even create style
+  // contexts for such content nodes, when text-combine-upright is not
+  // present.  However, not doing any rule matching for them is a first step.)
+  already_AddRefed<ComputedStyle> ResolveStyleForText(
+      nsIContent* aTextNode, ComputedStyle* aParentStyle);
+
+  // Get a ComputedStyle for a first-letter continuation (which no rules will
+  // match).
+  //
+  // The returned ComputedStyle will have
+  // nsCSSAnonBoxes::firstLetterContinuation() as its pseudo.
+  //
+  // (Perhaps nsCSSAnonBoxes::firstLetterContinuation() should go away and we
+  // shouldn't even create ComputedStyles for such frames.  However, not doing
+  // any rule matching for them is a first step.  And right now we do use this
+  // ComputedStyle for some things)
+  already_AddRefed<ComputedStyle> ResolveStyleForFirstLetterContinuation(
+      ComputedStyle* aParentStyle);
+
+  // Get a ComputedStyle for a placeholder frame (which no rules will match).
+  //
+  // The returned ComputedStyle will have nsCSSAnonBoxes::oofPlaceholder() as
+  // its pseudo.
+  //
+  // (Perhaps nsCSSAnonBoxes::oofPaceholder() should go away and we shouldn't
+  // even create ComputedStyle for placeholders.  However, not doing any rule
+  // matching for them is a first step.)
+  already_AddRefed<ComputedStyle> ResolveStyleForPlaceholder();
+
+  // Returns whether a given pseudo-element should exist or not.
+  static bool GeneratedContentPseudoExists(const ComputedStyle& aParentStyle,
+                                           const ComputedStyle& aPseudoStyle);
+
+  enum class IsProbe {
+    No,
+    Yes,
+  };
+
+  // Get a style for a pseudo-element.
+  //
+  // If IsProbe is Yes, then no style is returned if there are no rules matching
+  // for the pseudo-element, or GeneratedContentPseudoExists returns false.
+  //
+  // If IsProbe is No, then the style is guaranteed to be non-null.
+  already_AddRefed<ComputedStyle> ResolvePseudoElementStyle(
+      const dom::Element& aOriginatingElement, PseudoStyleType,
+      ComputedStyle* aParentStyle, IsProbe = IsProbe::No);
+
+  already_AddRefed<ComputedStyle> ProbePseudoElementStyle(
+      const dom::Element& aOriginatingElement, PseudoStyleType aType,
+      ComputedStyle* aParentStyle) {
+    return ResolvePseudoElementStyle(aOriginatingElement, aType, aParentStyle,
+                                     IsProbe::Yes);
+  }
+
+  // Resolves style for a (possibly-pseudo) Element without assuming that the
+  // style has been resolved. If the element was unstyled and a new style
+  // was resolved, it is not stored in the DOM. (That is, the element remains
+  // unstyled.)
+  already_AddRefed<ComputedStyle> ResolveStyleLazily(
+      const dom::Element&, PseudoStyleType = PseudoStyleType::NotPseudo,
+      StyleRuleInclusion = StyleRuleInclusion::All);
+
+  // Get a ComputedStyle for an anonymous box. The pseudo type must be an
+  // inheriting anon box.
+  already_AddRefed<ComputedStyle> ResolveInheritingAnonymousBoxStyle(
+      PseudoStyleType, ComputedStyle* aParentStyle);
+
+  // Get a ComputedStyle for an anonymous box. The pseudo type must be
+  // a non-inheriting anon box.
+  already_AddRefed<ComputedStyle> ResolveNonInheritingAnonymousBoxStyle(
+      PseudoStyleType aType) {
+    return ResolveNonInheritingAnonymousBoxStyle(aType, nullptr);
+  }
+
+  already_AddRefed<ComputedStyle> ResolvePageContentStyle(
+      const nsAtom* aPageName) {
+    return ResolveNonInheritingAnonymousBoxStyle(PseudoStyleType::pageContent,
+                                                 aPageName);
+  }
+
+  already_AddRefed<ComputedStyle> ResolveXULTreePseudoStyle(
+      dom::Element* aParentElement, nsCSSAnonBoxPseudoStaticAtom* aPseudoTag,
+      ComputedStyle* aParentStyle, const AtomArray& aInputWord);
+
+  size_t SheetCount(Origin) const;
+  StyleSheet* SheetAt(Origin, size_t aIndex) const;
+
+  // Gets the default orientation of CSS pages.
+  // This will return portrait or landscape both for a landscape/portrait
+  // value to page-size, as well as for an explicit size or paper name which
+  // is not square.
+  // If the value is auto or square, then returns nothing.
+  Maybe<StylePageSizeOrientation> GetDefaultPageSizeOrientation(
+      const nsAtom* aFirstPageName);
+
+  void AppendAllNonDocumentAuthorSheets(nsTArray<StyleSheet*>& aArray) const;
+
+  // Manage the set of style sheets in the style set
+  void AppendStyleSheet(StyleSheet&);
+  void InsertStyleSheetBefore(StyleSheet&, StyleSheet& aReferenceSheet);
+  void RemoveStyleSheet(StyleSheet&);
+  void AddDocStyleSheet(StyleSheet&);
+
+  /**
+   * Performs a Servo traversal to compute style for all dirty nodes in the
+   * document.
+   *
+   * This will traverse all of the document's style roots (that is, its document
+   * element, and the roots of the document-level native anonymous content).
+   *
+   * We specify |ForCSSRuleChanges| to try to update all CSS animations
+   * when we call this function due to CSS rule changes since @keyframes rules
+   * may have changed.
+   *
+   * Returns true if a post-traversal is required.
+   */
+  bool StyleDocument(ServoTraversalFlags aFlags);
+
+  /**
+   * Eagerly styles a subtree of unstyled nodes that was just appended to the
+   * tree. This is used in situations where we need the style immediately and
+   * cannot wait for a future batch restyle.
+   */
+  void StyleNewSubtree(dom::Element* aRoot);
+
+  /**
+   * Helper for correctly calling UpdateStylist without paying the cost of an
+   * extra function call in the common no-rebuild-needed case.
+   */
+  void UpdateStylistIfNeeded() {
+    if (StylistNeedsUpdate()) {
+      UpdateStylist();
+    }
+  }
+
+  /**
+   * Checks whether the rule tree has crossed its threshold for unused nodes,
+   * and if so, frees them.
+   */
+  void MaybeGCRuleTree();
+
+  /**
+   * Returns true if the given element may be used as the root of a style
+   * traversal. Reasons for false include having an unstyled parent, or having
+   * a parent that is display:none.
+   *
+   * Most traversal callsites don't need to check this, but some do.
+   */
+  static bool MayTraverseFrom(const dom::Element* aElement);
+
+#ifdef DEBUG
+  void AssertTreeIsClean();
+#else
+  void AssertTreeIsClean() {}
+#endif
+
+  /**
+   * Clears any cached style data that may depend on all sorts of computed
+   * values.
+   *
+   * Right now this clears the non-inheriting ComputedStyle cache, resets the
+   * default computed values, and clears cached anonymous content style.
+   *
+   * This does _not_, however, clear the stylist.
+   */
+  void ClearCachedStyleData();
+
+  /**
+   * Notifies the Servo stylesheet that the document's compatibility mode has
+   * changed.
+   */
+  void CompatibilityModeChanged();
+
+  template <typename T>
+  void EnumerateStyleSheets(T aCb) {
+    for (auto origin : kOrigins) {
+      for (size_t i = 0, count = SheetCount(origin); i < count; ++i) {
+        aCb(*SheetAt(origin, i));
+      }
+    }
+  }
+
+  /**
+   * Resolve style for the given element, and return it as a
+   * ComputedStyle.
+   *
+   * FIXME(emilio): Is there a point in this after bug 1367904?
+   */
+  static inline already_AddRefed<ComputedStyle> ResolveServoStyle(
+      const dom::Element&);
+
+  bool GetKeyframesForName(const dom::Element&, const ComputedStyle&,
+                           nsAtom* aName,
+                           const StyleComputedTimingFunction& aTimingFunction,
+                           nsTArray<Keyframe>& aKeyframes);
+
+  nsTArray<ComputedKeyframeValues> GetComputedKeyframeValuesFor(
+      const nsTArray<Keyframe>& aKeyframes, dom::Element* aElement,
+      PseudoStyleType aPseudoType, const ComputedStyle* aStyle);
+
+  void GetAnimationValues(
+      RawServoDeclarationBlock* aDeclarations, dom::Element* aElement,
+      const mozilla::ComputedStyle* aStyle,
+      nsTArray<RefPtr<RawServoAnimationValue>>& aAnimationValues);
+
+  void AppendFontFaceRules(nsTArray<nsFontFaceRuleContainer>& aArray);
+
+  const RawServoCounterStyleRule* CounterStyleRuleForName(nsAtom* aName);
+
+  // Get all the currently-active font feature values set.
+  already_AddRefed<gfxFontFeatureValueSet> BuildFontFeatureValueSet();
+
+  // Get the set of all currently-active font-palette-values.
+  already_AddRefed<gfx::FontPaletteValueSet> BuildFontPaletteValueSet();
+
+  already_AddRefed<ComputedStyle> GetBaseContextForElement(
+      dom::Element* aElement, const ComputedStyle* aStyle);
+
+  // Get a ComputedStyle that represents |aStyle|, but as though it additionally
+  // matched the rules of the newly added |aAnimaitonaValue|.
+  //
+  // We use this function to temporarily generate a ComputedStyle for
+  // calculating the cumulative change hints.
+  //
+  // This must hold:
+  //   The additional rules must be appropriate for the transition
+  //   level of the cascade, which is the highest level of the cascade.
+  //   (This is the case for one current caller, the cover rule used
+  //   for CSS transitions.)
+  // Note: |aElement| should be the generated element if it is pseudo.
+  already_AddRefed<ComputedStyle> ResolveServoStyleByAddingAnimation(
+      dom::Element* aElement, const ComputedStyle* aStyle,
+      RawServoAnimationValue* aAnimationValue);
+  /**
+   * Resolve style for a given declaration block with/without the parent style.
+   * If the parent style is not specified, the document default computed values
+   * is used.
+   */
+  already_AddRefed<ComputedStyle> ResolveForDeclarations(
+      const ComputedStyle* aParentOrNull,
+      const RawServoDeclarationBlock* aDeclarations);
+
+  already_AddRefed<RawServoAnimationValue> ComputeAnimationValue(
+      dom::Element* aElement, RawServoDeclarationBlock* aDeclaration,
+      const mozilla::ComputedStyle* aStyle);
+
+  void AppendTask(PostTraversalTask aTask) {
+    MOZ_ASSERT(IsInServoTraversal());
+
+    // We currently only use PostTraversalTasks while the Servo font metrics
+    // mutex is locked.  If we need to use them in other situations during
+    // a traversal, we should assert that we've taken appropriate
+    // synchronization measures.
+    AssertIsMainThreadOrServoFontMetricsLocked();
+
+    mPostTraversalTasks.AppendElement(aTask);
+  }
+
+  // Returns true if a restyle of the document is needed due to cloning
+  // sheet inners.
+  bool EnsureUniqueInnerOnCSSSheets();
+
+  // Returns the style rule map.
+  ServoStyleRuleMap* StyleRuleMap();
+
+  /**
+   * Returns true if a modification to an an attribute with the specified
+   * local name might require us to restyle the element.
+   *
+   * This function allows us to skip taking a an attribute snapshot when
+   * the modified attribute doesn't appear in an attribute selector in
+   * a style sheet.
+   */
+  bool MightHaveAttributeDependency(const dom::Element&,
+                                    nsAtom* aAttribute) const;
+
+  /**
+   * Returns true if a change in event state on an element might require
+   * us to restyle the element.
+   *
+   * This function allows us to skip taking a state snapshot when
+   * the changed state isn't depended upon by any pseudo-class selectors
+   * in a style sheet.
+   */
+  bool HasStateDependency(const dom::Element&, dom::ElementState) const;
+
+  /**
+   * Returns true if a change in document state might require us to restyle the
+   * document.
+   */
+  bool HasDocumentStateDependency(dom::DocumentState) const;
+
+  /**
+   * Get a new ComputedStyle that uses the same rules as the given ComputedStyle
+   * but has a different parent.
+   *
+   * aElement is non-null if this is a ComputedStyle for a frame whose mContent
+   * is an element and which has no pseudo on its ComputedStyle (so it's the
+   * actual style for the element being passed).
+   */
+  already_AddRefed<ComputedStyle> ReparentComputedStyle(
+      ComputedStyle* aComputedStyle, ComputedStyle* aNewParent,
+      ComputedStyle* aNewParentIgnoringFirstLine,
+      ComputedStyle* aNewLayoutParent, dom::Element* aElement);
+
+  /**
+   * Invalidate styles where there's any viewport units dependent style.
+   */
+  enum class OnlyDynamic : bool { No, Yes };
+  void InvalidateForViewportUnits(OnlyDynamic);
+
+ private:
+  friend class AutoSetInServoTraversal;
+  friend class AutoPrepareTraversal;
+  friend class PostTraversalTask;
+
+  bool ShouldTraverseInParallel() const;
+
+  void RuleChangedInternal(StyleSheet&, css::Rule&, StyleRuleChangeKind);
+
+  /**
+   * Forces all the ShadowRoot styles to be dirty.
+   *
+   * Only to be used for:
+   *
+   *  * Devtools (dealing with sheet cloning).
+   *  * Compatibility-mode changes.
+   *
+   * Try to do something more incremental for other callers that are exposed to
+   * the web.
+   */
+  void ForceDirtyAllShadowStyles();
+
+  /**
+   * Gets the pending snapshots to handle from the restyle manager.
+   */
+  const SnapshotTable& Snapshots();
+
+  /**
+   * Resolve all DeclarationBlocks attached to mapped
+   * presentation attributes cached on the document.
+   *
+   * Call this before jumping into Servo's style system.
+   */
+  void ResolveMappedAttrDeclarationBlocks();
+
+  /**
+   * Clear our cached mNonInheritingComputedStyles.
+   *
+   * We do this when we want to make sure those ComputedStyles won't live too
+   * long (e.g. when rebuilding all style data or when shutting down the style
+   * set).
+   */
+  void ClearNonInheritingComputedStyles();
+
+  /**
+   * Perform processes that we should do before traversing.
+   *
+   * When aRoot is null, the entire document is pre-traversed.  Otherwise,
+   * only the subtree rooted at aRoot is pre-traversed.
+   */
+  void PreTraverse(ServoTraversalFlags aFlags, dom::Element* aRoot = nullptr);
+
+  // Subset of the pre-traverse steps that involve syncing up data
+  void PreTraverseSync();
+
+  /**
+   * Records that the contents of style sheets at the specified origin have
+   * changed since the last.  Calling this will ensure that the Stylist
+   * rebuilds its selector maps.
+   */
+  void MarkOriginsDirty(OriginFlags aChangedOrigins);
+
+  /**
+   * Note that the stylist needs a style flush due to style sheet changes.
+   */
+  void SetStylistStyleSheetsDirty();
+
+  void SetStylistShadowDOMStyleSheetsDirty();
+
+  bool StylistNeedsUpdate() const {
+    return mStylistState != StylistState::NotDirty;
+  }
+
+  /**
+   * Update the stylist as needed to ensure style data is up-to-date.
+   *
+   * This should only be called if StylistNeedsUpdate returns true.
+   */
+  void UpdateStylist();
+
+  void RunPostTraversalTasks();
+
+  void PrependSheetOfType(Origin, StyleSheet*);
+  void AppendSheetOfType(Origin, StyleSheet*);
+  void InsertSheetOfType(Origin, StyleSheet*, StyleSheet* aBeforeSheet);
+  void RemoveSheetOfType(Origin, StyleSheet*);
+
+  const nsPresContext* GetPresContext() const {
+    return const_cast<ServoStyleSet*>(this)->GetPresContext();
+  }
+
+  /**
+   * Return the associated pres context if we're the master style set and we
+   * have an associated pres shell.
+   */
+  nsPresContext* GetPresContext();
+
+  // The owner document of this style set. Never null, and always outlives the
+  // StyleSet.
+  dom::Document* mDocument;
+  UniquePtr<RawServoStyleSet> mRawSet;
+
+  // Map from raw Servo style rule to Gecko's wrapper object.
+  // Constructed lazily when requested by devtools.
+  UniquePtr<ServoStyleRuleMap> mStyleRuleMap;
+  uint64_t mUserFontSetUpdateGeneration = 0;
+
+  // Tasks to perform after a traversal, back on the main thread.
+  //
+  // These are similar to Servo's SequentialTasks, except that they are
+  // posted by C++ code running on style worker threads.
+  nsTArray<PostTraversalTask> mPostTraversalTasks;
+
+  // Stores pointers to our cached ComputedStyles for non-inheriting anonymous
+  // boxes.
+  EnumeratedArray<nsCSSAnonBoxes::NonInheriting,
+                  nsCSSAnonBoxes::NonInheriting::_Count, RefPtr<ComputedStyle>>
+      mNonInheritingComputedStyles;
+
+  already_AddRefed<ComputedStyle> ResolveNonInheritingAnonymousBoxStyle(
+      PseudoStyleType aType, const nsAtom* aPageName);
+
+ public:
+  void PutCachedAnonymousContentStyles(
+      AnonymousContentKey aKey, nsTArray<RefPtr<ComputedStyle>>&& aStyles) {
+    auto index = static_cast<size_t>(aKey);
+
+    MOZ_ASSERT(mCachedAnonymousContentStyles.Length() + aStyles.Length() < 256,
+               "(index, length) pairs must be bigger");
+    MOZ_ASSERT(mCachedAnonymousContentStyleIndexes[index].second == 0,
+               "shouldn't need to overwrite existing cached styles");
+    MOZ_ASSERT(!aStyles.IsEmpty(), "should have some styles to cache");
+
+    mCachedAnonymousContentStyleIndexes[index] = std::make_pair(
+        mCachedAnonymousContentStyles.Length(), aStyles.Length());
+    mCachedAnonymousContentStyles.AppendElements(std::move(aStyles));
+  }
+
+  void GetCachedAnonymousContentStyles(
+      AnonymousContentKey aKey, nsTArray<RefPtr<ComputedStyle>>& aStyles) {
+    auto index = static_cast<size_t>(aKey);
+    auto loc = mCachedAnonymousContentStyleIndexes[index];
+    aStyles.AppendElements(mCachedAnonymousContentStyles.Elements() + loc.first,
+                           loc.second);
+  }
+
+ private:
+  // Map of AnonymousContentKey values to an (index, length) pair pointing into
+  // mCachedAnonymousContentStyles.
+  //
+  // We assert that the index and length values fit into uint8_ts.
+  Array<std::pair<uint8_t, uint8_t>, 1 << sizeof(AnonymousContentKey) * 8>
+      mCachedAnonymousContentStyleIndexes;
+
+  // Stores cached ComputedStyles for certain native anonymous content.
+  nsTArray<RefPtr<ComputedStyle>> mCachedAnonymousContentStyles;
+
+  StylistState mStylistState = StylistState::NotDirty;
+  bool mAuthorStyleDisabled = false;
+  bool mNeedsRestyleAfterEnsureUniqueInner = false;
+};
+
+class UACacheReporter final : public nsIMemoryReporter {
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIMEMORYREPORTER
+
+ private:
+  ~UACacheReporter() = default;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_ServoStyleSet_h