Add m-esr52 at 52.6.0

1 files changed, 853 insertions, 0 deletions

diff --git a/layout/style/nsStyleContext.h b/layout/style/nsStyleContext.h
new file mode 100644
index 0000000000..b0b4896a3d
--- /dev/null
+++ b/layout/style/nsStyleContext.h
@@ -0,0 +1,853 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+/* the interface (to internal code) for retrieving computed style data */
+
+#ifndef _nsStyleContext_h_
+#define _nsStyleContext_h_
+
+#include "mozilla/Assertions.h"
+#include "mozilla/RestyleLogging.h"
+#include "mozilla/StyleContextSource.h"
+#include "nsCSSAnonBoxes.h"
+#include "nsStyleSet.h"
+
+class nsIAtom;
+class nsPresContext;
+
+namespace mozilla {
+enum class CSSPseudoElementType : uint8_t;
+} // namespace mozilla
+
+extern "C" {
+#define STYLE_STRUCT(name_, checkdata_cb_)     \
+  struct nsStyle##name_;                       \
+  const nsStyle##name_* Servo_GetStyle##name_( \
+    ServoComputedValuesBorrowedOrNull computed_values);
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+}
+
+/**
+ * An nsStyleContext represents the computed style data for an element.
+ * The computed style data are stored in a set of structs (see
+ * nsStyleStruct.h) that are cached either on the style context or in
+ * the rule tree (see nsRuleNode.h for a description of this caching and
+ * how the cached structs are shared).
+ *
+ * Since the data in |nsIStyleRule|s and |nsRuleNode|s are immutable
+ * (with a few exceptions, like system color changes), the data in an
+ * nsStyleContext are also immutable (with the additional exception of
+ * GetUniqueStyleData).  When style data change,
+ * ElementRestyler::Restyle creates a new style context.
+ *
+ * Style contexts are reference counted.  References are generally held
+ * by:
+ *  1. the |nsIFrame|s that are using the style context and
+ *  2. any *child* style contexts (this might be the reverse of
+ *     expectation, but it makes sense in this case)
+ */
+
+class nsStyleContext final
+{
+public:
+  /**
+   * Create a new style context.
+   * @param aParent  The parent of a style context is used for CSS
+   *                 inheritance.  When the element or pseudo-element
+   *                 this style context represents the style data of
+   *                 inherits a CSS property, the value comes from the
+   *                 parent style context.  This means style context
+   *                 parentage must match the definitions of inheritance
+   *                 in the CSS specification.
+   * @param aPseudoTag  The pseudo-element or anonymous box for which
+   *                    this style context represents style.  Null if
+   *                    this style context is for a normal DOM element.
+   * @param aPseudoType  Must match aPseudoTag.
+   * @param aRuleNode  A rule node representing the ordered sequence of
+   *                   rules that any element, pseudo-element, or
+   *                   anonymous box that this style context is for
+   *                   matches.  See |nsRuleNode| and |nsIStyleRule|.
+   * @param aSkipParentDisplayBasedStyleFixup
+   *                 If set, this flag indicates that we should skip
+   *                 the chunk of ApplyStyleFixups() that applies to
+   *                 special cases where a child element's style may
+   *                 need to be modified based on its parent's display
+   *                 value.
+   */
+  nsStyleContext(nsStyleContext* aParent, nsIAtom* aPseudoTag,
+                 mozilla::CSSPseudoElementType aPseudoType,
+                 already_AddRefed<nsRuleNode> aRuleNode,
+                 bool aSkipParentDisplayBasedStyleFixup);
+
+  // Version of the above that takes a ServoComputedValues instead of a Gecko
+  // nsRuleNode.
+  nsStyleContext(nsStyleContext* aParent,
+                 nsPresContext* aPresContext,
+                 nsIAtom* aPseudoTag,
+                 mozilla::CSSPseudoElementType aPseudoType,
+                 already_AddRefed<ServoComputedValues> aComputedValues,
+                 bool aSkipParentDisplayBasedStyleFixup);
+
+  void* operator new(size_t sz, nsPresContext* aPresContext);
+  void Destroy();
+
+  // These two methods are for use by ArenaRefPtr.
+  static mozilla::ArenaObjectID ArenaObjectID()
+  {
+    return mozilla::eArenaObjectID_nsStyleContext;
+  }
+  nsIPresShell* Arena();
+
+#ifdef DEBUG
+  /**
+   * Initializes a cached pref, which is only used in DEBUG code.
+   */
+  static void Initialize();
+#endif
+
+  nsrefcnt AddRef() {
+    if (mRefCnt == UINT32_MAX) {
+      NS_WARNING("refcount overflow, leaking object");
+      return mRefCnt;
+    }
+    ++mRefCnt;
+    NS_LOG_ADDREF(this, mRefCnt, "nsStyleContext", sizeof(nsStyleContext));
+    return mRefCnt;
+  }
+
+  nsrefcnt Release() {
+    if (mRefCnt == UINT32_MAX) {
+      NS_WARNING("refcount overflow, leaking object");
+      return mRefCnt;
+    }
+    --mRefCnt;
+    NS_LOG_RELEASE(this, mRefCnt, "nsStyleContext");
+    if (mRefCnt == 0) {
+      Destroy();
+      return 0;
+    }
+    return mRefCnt;
+  }
+
+#ifdef DEBUG
+  void FrameAddRef() {
+    ++mFrameRefCnt;
+  }
+
+  void FrameRelease() {
+    --mFrameRefCnt;
+  }
+
+  uint32_t FrameRefCnt() const {
+    return mFrameRefCnt;
+  }
+#endif
+
+  bool HasSingleReference() const {
+    NS_ASSERTION(mRefCnt != 0,
+                 "do not call HasSingleReference on a newly created "
+                 "nsStyleContext with no references yet");
+    return mRefCnt == 1;
+  }
+
+  nsPresContext* PresContext() const {
+#ifdef MOZ_STYLO
+    return mPresContext;
+#else
+    return mSource.AsGeckoRuleNode()->PresContext();
+#endif
+  }
+
+  nsStyleContext* GetParent() const { return mParent; }
+
+  nsIAtom* GetPseudo() const { return mPseudoTag; }
+  mozilla::CSSPseudoElementType GetPseudoType() const {
+    return static_cast<mozilla::CSSPseudoElementType>(
+             mBits >> NS_STYLE_CONTEXT_TYPE_SHIFT);
+  }
+
+  bool IsAnonBox() const {
+    return GetPseudoType() == mozilla::CSSPseudoElementType::AnonBox;
+  }
+  bool IsPseudoElement() const { return mPseudoTag && !IsAnonBox(); }
+
+
+  // Find, if it already exists *and is easily findable* (i.e., near the
+  // start of the child list), a style context whose:
+  //  * GetPseudo() matches aPseudoTag
+  //  * mSource matches aSource
+  //  * !!GetStyleIfVisited() == !!aSourceIfVisited, and, if they're
+  //    non-null, GetStyleIfVisited()->mSource == aSourceIfVisited
+  //  * RelevantLinkVisited() == aRelevantLinkVisited
+  already_AddRefed<nsStyleContext>
+  FindChildWithRules(const nsIAtom* aPseudoTag,
+                     mozilla::NonOwningStyleContextSource aSource,
+                     mozilla::NonOwningStyleContextSource aSourceIfVisited,
+                     bool aRelevantLinkVisited);
+
+  // Does this style context or any of its ancestors have text
+  // decoration lines?
+  // Differs from nsStyleTextReset::HasTextDecorationLines, which tests
+  // only the data for a single context.
+  bool HasTextDecorationLines() const
+    { return !!(mBits & NS_STYLE_HAS_TEXT_DECORATION_LINES); }
+
+  // Whether any line break inside should be suppressed? If this returns
+  // true, the line should not be broken inside, which means inlines act
+  // as if nowrap is set, <br> is suppressed, and blocks are inlinized.
+  // This bit is propogated to all children of line partitipants. It is
+  // currently used by ruby to make its content frames unbreakable.
+  // NOTE: for nsTextFrame, use nsTextFrame::ShouldSuppressLineBreak()
+  // instead of this method.
+  bool ShouldSuppressLineBreak() const
+    { return !!(mBits & NS_STYLE_SUPPRESS_LINEBREAK); }
+
+  // Does this style context or any of its ancestors have display:none set?
+  bool IsInDisplayNoneSubtree() const
+    { return !!(mBits & NS_STYLE_IN_DISPLAY_NONE_SUBTREE); }
+
+  // Is this horizontal-in-vertical (tate-chu-yoko) text? This flag is
+  // only set on style contexts whose pseudo is nsCSSAnonBoxes::mozText.
+  bool IsTextCombined() const
+    { return !!(mBits & NS_STYLE_IS_TEXT_COMBINED); }
+
+  // Does this style context represent the style for a pseudo-element or
+  // inherit data from such a style context?  Whether this returns true
+  // is equivalent to whether it or any of its ancestors returns
+  // non-null for IsPseudoElement().
+  bool HasPseudoElementData() const
+    { return !!(mBits & NS_STYLE_HAS_PSEUDO_ELEMENT_DATA); }
+
+  bool HasChildThatUsesResetStyle() const
+    { return mBits & NS_STYLE_HAS_CHILD_THAT_USES_RESET_STYLE; }
+
+  // Is the only link whose visitedness is allowed to influence the
+  // style of the node this style context is for (which is that element
+  // or its nearest ancestor that is a link) visited?
+  bool RelevantLinkVisited() const
+    { return !!(mBits & NS_STYLE_RELEVANT_LINK_VISITED); }
+
+  // Is this a style context for a link?
+  bool IsLinkContext() const {
+    return
+      GetStyleIfVisited() && GetStyleIfVisited()->GetParent() == GetParent();
+  }
+
+  // Is this style context the GetStyleIfVisited() for some other style
+  // context?
+  bool IsStyleIfVisited() const
+    { return !!(mBits & NS_STYLE_IS_STYLE_IF_VISITED); }
+
+  // Tells this style context that it should return true from
+  // IsStyleIfVisited.
+  void SetIsStyleIfVisited()
+    { mBits |= NS_STYLE_IS_STYLE_IF_VISITED; }
+
+  // Return the style context whose style data should be used for the R,
+  // G, and B components of color, background-color, and border-*-color
+  // if RelevantLinkIsVisited().
+  //
+  // GetPseudo() and GetPseudoType() on this style context return the
+  // same as on |this|, and its depth in the tree (number of GetParent()
+  // calls until null is returned) is the same as |this|, since its
+  // parent is either |this|'s parent or |this|'s parent's
+  // style-if-visited.
+  //
+  // Structs on this context should never be examined without also
+  // examining the corresponding struct on |this|.  Doing so will likely
+  // both (1) lead to a privacy leak and (2) lead to dynamic change bugs
+  // related to the Peek code in nsStyleContext::CalcStyleDifference.
+  nsStyleContext* GetStyleIfVisited() const
+    { return mStyleIfVisited; }
+
+  // To be called only from nsStyleSet.
+  void SetStyleIfVisited(already_AddRefed<nsStyleContext> aStyleIfVisited)
+  {
+    MOZ_ASSERT(!IsStyleIfVisited(), "this context is not visited data");
+    NS_ASSERTION(!mStyleIfVisited, "should only be set once");
+
+    mStyleIfVisited = aStyleIfVisited;
+
+    MOZ_ASSERT(mStyleIfVisited->IsStyleIfVisited(),
+               "other context is visited data");
+    MOZ_ASSERT(!mStyleIfVisited->GetStyleIfVisited(),
+               "other context does not have visited data");
+    NS_ASSERTION(GetStyleIfVisited()->GetPseudo() == GetPseudo(),
+                 "pseudo tag mismatch");
+    if (GetParent() && GetParent()->GetStyleIfVisited()) {
+      NS_ASSERTION(GetStyleIfVisited()->GetParent() ==
+                     GetParent()->GetStyleIfVisited() ||
+                   GetStyleIfVisited()->GetParent() == GetParent(),
+                   "parent mismatch");
+    } else {
+      NS_ASSERTION(GetStyleIfVisited()->GetParent() == GetParent(),
+                   "parent mismatch");
+    }
+  }
+
+  // Does any descendant of this style context have any style values
+  // that were computed based on this style context's ancestors?
+  bool HasChildThatUsesGrandancestorStyle() const
+    { return !!(mBits & NS_STYLE_CHILD_USES_GRANDANCESTOR_STYLE); }
+
+  // Is this style context shared with a sibling or cousin?
+  // (See nsStyleSet::GetContext.)
+  bool IsShared() const
+    { return !!(mBits & NS_STYLE_IS_SHARED); }
+
+  // Tell this style context to cache aStruct as the struct for aSID
+  void SetStyle(nsStyleStructID aSID, void* aStruct);
+
+  /**
+   * Returns whether this style context has cached style data for a
+   * given style struct and it does NOT own that struct.  This can
+   * happen because it was inherited from the parent style context, or
+   * because it was stored conditionally on the rule node.
+   */
+  bool HasCachedDependentStyleData(nsStyleStructID aSID) {
+    return mBits & nsCachedStyleData::GetBitForSID(aSID);
+  }
+
+  nsRuleNode* RuleNode() {
+    MOZ_RELEASE_ASSERT(mSource.IsGeckoRuleNode());
+    return mSource.AsGeckoRuleNode();
+  }
+
+  void AddStyleBit(const uint64_t& aBit) { mBits |= aBit; }
+
+  /*
+   * Get the style data for a style struct.  This is the most important
+   * member function of nsStyleContext.  It fills in a const pointer
+   * to a style data struct that is appropriate for the style context's
+   * frame.  This struct may be shared with other contexts (either in
+   * the rule tree or the style context tree), so it should not be
+   * modified.
+   *
+   * This function will NOT return null (even when out of memory) when
+   * given a valid style struct ID, so the result does not need to be
+   * null-checked.
+   *
+   * The typesafe functions below are preferred to the use of this
+   * function, both because they're easier to read and because they're
+   * faster.
+   */
+  const void* NS_FASTCALL StyleData(nsStyleStructID aSID);
+
+  /**
+   * Define typesafe getter functions for each style struct by
+   * preprocessing the list of style structs.  These functions are the
+   * preferred way to get style data.  The macro creates functions like:
+   *   const nsStyleBorder* StyleBorder();
+   *   const nsStyleColor* StyleColor();
+   */
+  #define STYLE_STRUCT(name_, checkdata_cb_)              \
+    const nsStyle##name_ * Style##name_() {               \
+      return DoGetStyle##name_<true>();                   \
+    }
+  #include "nsStyleStructList.h"
+  #undef STYLE_STRUCT
+
+  /**
+   * PeekStyle* is like Style* but doesn't trigger style
+   * computation if the data is not cached on either the style context
+   * or the rule node.
+   *
+   * Perhaps this shouldn't be a public nsStyleContext API.
+   */
+  #define STYLE_STRUCT(name_, checkdata_cb_)              \
+    const nsStyle##name_ * PeekStyle##name_() {           \
+      return DoGetStyle##name_<false>();                  \
+    }
+  #include "nsStyleStructList.h"
+  #undef STYLE_STRUCT
+
+  /**
+   * Compute the style changes needed during restyling when this style
+   * context is being replaced by aNewContext.  (This is nonsymmetric since
+   * we optimize by skipping comparison for styles that have never been
+   * requested.)
+   *
+   * This method returns a change hint (see nsChangeHint.h).  All change
+   * hints apply to the frame and its later continuations or ib-split
+   * siblings.  Most (all of those except the "NotHandledForDescendants"
+   * hints) also apply to all descendants.  The caller must pass in any
+   * non-inherited hints that resulted from the parent style context's
+   * style change.  The caller *may* pass more hints than needed, but
+   * must not pass less than needed; therefore if the caller doesn't
+   * know, the caller should pass
+   * nsChangeHint_Hints_NotHandledForDescendants.
+   *
+   * aEqualStructs must not be null.  Into it will be stored a bitfield
+   * representing which structs were compared to be non-equal.
+   */
+  nsChangeHint CalcStyleDifference(nsStyleContext* aNewContext,
+                                   nsChangeHint aParentHintsNotHandledForDescendants,
+                                   uint32_t* aEqualStructs,
+                                   uint32_t* aSamePointerStructs);
+
+  /**
+   * Like the above, but allows comparing ServoComputedValues instead of needing
+   * a full-fledged style context.
+   */
+  nsChangeHint CalcStyleDifference(const ServoComputedValues* aNewComputedValues,
+                                   nsChangeHint aParentHintsNotHandledForDescendants,
+                                   uint32_t* aEqualStructs,
+                                   uint32_t* aSamePointerStructs);
+
+private:
+  template<class StyleContextLike>
+  nsChangeHint CalcStyleDifferenceInternal(StyleContextLike* aNewContext,
+                                           nsChangeHint aParentHintsNotHandledForDescendants,
+                                           uint32_t* aEqualStructs,
+                                           uint32_t* aSamePointerStructs);
+
+public:
+  /**
+   * Get a color that depends on link-visitedness using this and
+   * this->GetStyleIfVisited().
+   *
+   * aProperty must be a color-valued property that StyleAnimationValue
+   * knows how to extract.  It must also be a property that we know to
+   * do change handling for in nsStyleContext::CalcDifference.
+   */
+  nscolor GetVisitedDependentColor(nsCSSPropertyID aProperty);
+
+  /**
+   * aColors should be a two element array of nscolor in which the first
+   * color is the unvisited color and the second is the visited color.
+   *
+   * Combine the R, G, and B components of whichever of aColors should
+   * be used based on aLinkIsVisited with the A component of aColors[0].
+   */
+  static nscolor CombineVisitedColors(nscolor *aColors,
+                                      bool aLinkIsVisited);
+
+  /**
+   * Start the background image loads for this style context.
+   */
+  void StartBackgroundImageLoads() {
+    // Just get our background struct; that should do the trick
+    StyleBackground();
+  }
+
+  /**
+   * Moves this style context to a new parent.
+   *
+   * This function violates style context tree immutability, and
+   * is a very low-level function and should only be used after verifying
+   * many conditions that make it safe to call.
+   */
+  void MoveTo(nsStyleContext* aNewParent);
+
+  /**
+   * Swaps owned style struct pointers between this and aNewContext, on
+   * the assumption that aNewContext is the new style context for a frame
+   * and this is the old one.  aStructs indicates which structs to consider
+   * swapping; only those which are owned in both this and aNewContext
+   * will be swapped.
+   *
+   * Additionally, if there are identical struct pointers for one of the
+   * structs indicated by aStructs, and it is not an owned struct on this,
+   * then the cached struct slot on this will be set to null.  If the struct
+   * has been swapped on an ancestor, this style context (being the old one)
+   * will be left caching the struct pointer on the new ancestor, despite
+   * inheriting from the old ancestor.  This is not normally a problem, as
+   * this style context will usually be destroyed by being released at the
+   * end of ElementRestyler::Restyle; but for style contexts held on to outside
+   * of the frame, we need to clear out the cached pointer so that if we need
+   * it again we'll re-fetch it from the new ancestor.
+   */
+  void SwapStyleData(nsStyleContext* aNewContext, uint32_t aStructs);
+
+  /**
+   * On each descendant of this style context, clears out any cached inherited
+   * structs indicated in aStructs.
+   */
+  void ClearCachedInheritedStyleDataOnDescendants(uint32_t aStructs);
+
+  /**
+   * Sets the NS_STYLE_INELIGIBLE_FOR_SHARING bit on this style context
+   * and its descendants.  If it finds a descendant that has the bit
+   * already set, assumes that it can skip that subtree.
+   */
+  void SetIneligibleForSharing();
+
+#ifdef DEBUG
+  void List(FILE* out, int32_t aIndent, bool aListDescendants = true);
+  static void AssertStyleStructMaxDifferenceValid();
+  static const char* StructName(nsStyleStructID aSID);
+  static bool LookupStruct(const nsACString& aName, nsStyleStructID& aResult);
+#endif
+
+#ifdef RESTYLE_LOGGING
+  nsCString GetCachedStyleDataAsString(uint32_t aStructs);
+  void LogStyleContextTree(int32_t aLoggingDepth, uint32_t aStructs);
+  int32_t& LoggingDepth();
+#endif
+
+  /**
+   * Return style data that is currently cached on the style context.
+   * Only returns the structs we cache ourselves; never consults the
+   * rule tree.
+   *
+   * For "internal" use only in nsStyleContext and nsRuleNode.
+   */
+  const void* GetCachedStyleData(nsStyleStructID aSID)
+  {
+    const void* cachedData;
+    if (nsCachedStyleData::IsReset(aSID)) {
+      if (mCachedResetData) {
+        cachedData = mCachedResetData->mStyleStructs[aSID];
+      } else {
+        cachedData = nullptr;
+      }
+    } else {
+      cachedData = mCachedInheritedData.mStyleStructs[aSID];
+    }
+    return cachedData;
+  }
+
+  mozilla::NonOwningStyleContextSource StyleSource() const { return mSource.AsRaw(); }
+
+#ifdef MOZ_STYLO
+  // NOTE: It'd be great to assert here that the previous change hint is always
+  // consumed.
+  //
+  // This is not the case right now, since the changes of childs of frames that
+  // go through frame construction are not consumed.
+  void StoreChangeHint(nsChangeHint aHint)
+  {
+    MOZ_ASSERT(!IsShared());
+    mStoredChangeHint = aHint;
+#ifdef DEBUG
+    mConsumedChangeHint = false;
+#endif
+  }
+
+  nsChangeHint ConsumeStoredChangeHint()
+  {
+    MOZ_ASSERT(!mConsumedChangeHint, "Re-consuming the same change hint!");
+    nsChangeHint result = mStoredChangeHint;
+    mStoredChangeHint = nsChangeHint(0);
+#ifdef DEBUG
+    mConsumedChangeHint = true;
+#endif
+    return result;
+  }
+#else
+  void StoreChangeHint(nsChangeHint aHint)
+  {
+    MOZ_CRASH("stylo: Called nsStyleContext::StoreChangeHint in a non MOZ_STYLO "
+              "build.");
+  }
+
+  nsChangeHint ConsumeStoredChangeHint()
+  {
+    MOZ_CRASH("stylo: Called nsStyleContext::ComsumeStoredChangeHint in a non "
+               "MOZ_STYLO build.");
+  }
+#endif
+
+private:
+  // Private destructor, to discourage deletion outside of Release():
+  ~nsStyleContext();
+
+  // Delegated Helper constructor.
+  nsStyleContext(nsStyleContext* aParent,
+                 mozilla::OwningStyleContextSource&& aSource,
+                 nsIAtom* aPseudoTag,
+                 mozilla::CSSPseudoElementType aPseudoType);
+
+  // Helper post-contruct hook.
+  void FinishConstruction(bool aSkipParentDisplayBasedStyleFixup);
+
+  void AddChild(nsStyleContext* aChild);
+  void RemoveChild(nsStyleContext* aChild);
+
+  void* GetUniqueStyleData(const nsStyleStructID& aSID);
+  void* CreateEmptyStyleData(const nsStyleStructID& aSID);
+
+  void SetStyleBits();
+  void ApplyStyleFixups(bool aSkipParentDisplayBasedStyleFixup);
+
+  const void* StyleStructFromServoComputedValues(nsStyleStructID aSID) {
+    switch (aSID) {
+#define STYLE_STRUCT(name_, checkdata_cb_)                                    \
+      case eStyleStruct_##name_:                                              \
+        return Servo_GetStyle##name_(mSource.AsServoComputedValues());
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+      default:
+        MOZ_ASSERT_UNREACHABLE("unexpected nsStyleStructID value");
+        return nullptr;
+    }
+  }
+
+#ifdef DEBUG
+  struct AutoCheckDependency {
+
+    nsStyleContext* mStyleContext;
+    nsStyleStructID mOuterSID;
+
+    AutoCheckDependency(nsStyleContext* aContext, nsStyleStructID aInnerSID)
+      : mStyleContext(aContext)
+    {
+      mOuterSID = aContext->mComputingStruct;
+      MOZ_ASSERT(mOuterSID == nsStyleStructID_None ||
+                 DependencyAllowed(mOuterSID, aInnerSID),
+                 "Undeclared dependency, see generate-stylestructlist.py");
+      aContext->mComputingStruct = aInnerSID;
+    }
+
+    ~AutoCheckDependency()
+    {
+      mStyleContext->mComputingStruct = mOuterSID;
+    }
+
+  };
+
+#define AUTO_CHECK_DEPENDENCY(sid_) \
+  AutoCheckDependency checkNesting_(this, sid_)
+#else
+#define AUTO_CHECK_DEPENDENCY(sid_)
+#endif
+
+  // Helper functions for GetStyle* and PeekStyle*
+  #define STYLE_STRUCT_INHERITED(name_, checkdata_cb_)                  \
+    template<bool aComputeData>                                         \
+    const nsStyle##name_ * DoGetStyle##name_() {                        \
+      const nsStyle##name_ * cachedData =                               \
+        static_cast<nsStyle##name_*>(                                   \
+          mCachedInheritedData.mStyleStructs[eStyleStruct_##name_]);    \
+      if (cachedData) /* Have it cached already, yay */                 \
+        return cachedData;                                              \
+      if (!aComputeData) {                                              \
+        /* We always cache inherited structs on the context when we */  \
+        /* compute them. */                                             \
+        return nullptr;                                                 \
+      }                                                                 \
+      /* Have the rulenode deal */                                      \
+      AUTO_CHECK_DEPENDENCY(eStyleStruct_##name_);                      \
+      const nsStyle##name_ * newData;                                   \
+      if (mSource.IsGeckoRuleNode()) {                                  \
+        newData = mSource.AsGeckoRuleNode()->                           \
+          GetStyle##name_<aComputeData>(this, mBits);                   \
+      } else {                                                          \
+        /**                                                             \
+         * Reach the parent to grab the inherited style struct if       \
+         * we're a text node.                                           \
+         *                                                              \
+         * This causes the parent element's style context to cache any  \
+         * inherited structs we request for a text node, which means we \
+         * don't have to compute change hints for the text node, as     \
+         * handling the change on the parent element is sufficient.     \
+         *                                                              \
+         * Note that adding the inherit bit is ok, because the struct   \
+         * pointer returned by the parent and the child is owned by     \
+         * Servo. This is fine if the pointers are the same (as it      \
+         * should, read below), because both style context sources will \
+         * hold it.                                                     \
+         *                                                              \
+         * In the case of a mishandled frame, we could end up with the  \
+         * pointer to and old parent style, but that's fine too, since  \
+         * the parent style context will remain alive until we reframe, \
+         * in which case we'll discard both style contexts. Also, we    \
+         * hold a strong reference to the parent style context, which   \
+         * makes it a non-issue.                                        \
+         *                                                              \
+         * Also, note that the assertion below should be true, except   \
+         * for those frames we still don't handle correctly, like       \
+         * anonymous table wrappers, in which case the pointers will    \
+         * differ.                                                      \
+         *                                                              \
+         * That means we're not going to restyle correctly text frames  \
+         * of anonymous table wrappers, for example. It's kind of       \
+         * embarrassing, but I think it's not worth it to add more      \
+         * logic here unconditionally, given that's going to be fixed.  \
+         *                                                              \
+         * TODO(emilio): Convert to a strong assertion once we support  \
+         * all kinds of random frames. In fact, this can be a great     \
+         * assertion to debug them.                                     \
+         */                                                             \
+        if (mPseudoTag == nsCSSAnonBoxes::mozText) {                    \
+          MOZ_ASSERT(mParent);                                          \
+          newData = mParent->DoGetStyle##name_<true>();                 \
+          NS_WARNING_ASSERTION(                                         \
+            newData == Servo_GetStyle##name_(mSource.AsServoComputedValues()), \
+            "bad newData");                                             \
+        } else {                                                        \
+          newData =                                                     \
+            Servo_GetStyle##name_(mSource.AsServoComputedValues());     \
+        }                                                               \
+        /* perform any remaining main thread work on the struct */      \
+        const_cast<nsStyle##name_*>(newData)->FinishStyle(PresContext());\
+        /* the Servo-backed StyleContextSource owns the struct */       \
+        AddStyleBit(NS_STYLE_INHERIT_BIT(name_));                       \
+      }                                                                 \
+      /* always cache inherited data on the style context; the rule */  \
+      /* node set the bit in mBits for us if needed. */                 \
+      mCachedInheritedData.mStyleStructs[eStyleStruct_##name_] =        \
+        const_cast<nsStyle##name_ *>(newData);                          \
+      return newData;                                                   \
+    }
+  #define STYLE_STRUCT_RESET(name_, checkdata_cb_)                      \
+    template<bool aComputeData>                                         \
+    const nsStyle##name_ * DoGetStyle##name_() {                        \
+      if (mCachedResetData) {                                           \
+        const nsStyle##name_ * cachedData =                             \
+          static_cast<nsStyle##name_*>(                                 \
+            mCachedResetData->mStyleStructs[eStyleStruct_##name_]);     \
+        if (cachedData) /* Have it cached already, yay */               \
+          return cachedData;                                            \
+      }                                                                 \
+      /* Have the rulenode deal */                                      \
+      AUTO_CHECK_DEPENDENCY(eStyleStruct_##name_);                      \
+      const nsStyle##name_ * newData;                                   \
+      if (mSource.IsGeckoRuleNode()) {                                  \
+        newData = mSource.AsGeckoRuleNode()->                           \
+          GetStyle##name_<aComputeData>(this);                          \
+      } else {                                                          \
+        newData =                                                       \
+          Servo_GetStyle##name_(mSource.AsServoComputedValues());       \
+        /* perform any remaining main thread work on the struct */      \
+        const_cast<nsStyle##name_*>(newData)->FinishStyle(PresContext());\
+        /* The Servo-backed StyleContextSource owns the struct.         \
+         *                                                              \
+         * XXXbholley: Unconditionally caching reset structs here       \
+         * defeats the memory optimization where we lazily allocate     \
+         * mCachedResetData, so that we can avoid performing an FFI     \
+         * call each time we want to get the style structs. We should   \
+         * measure the tradeoffs at some point. If the FFI overhead is  \
+         * low and the memory win significant, we should consider       \
+         * _always_ grabbing the struct over FFI, and potentially       \
+         * giving mCachedInheritedData the same treatment.              \
+         *                                                              \
+         * Note that there is a similar comment in StyleData().         \
+         */                                                             \
+        AddStyleBit(NS_STYLE_INHERIT_BIT(name_));                       \
+        SetStyle(eStyleStruct_##name_,                                  \
+                 const_cast<nsStyle##name_*>(newData));                 \
+      }                                                                 \
+      return newData;                                                   \
+    }
+  #include "nsStyleStructList.h"
+  #undef STYLE_STRUCT_RESET
+  #undef STYLE_STRUCT_INHERITED
+
+  // Helper for ClearCachedInheritedStyleDataOnDescendants.
+  void DoClearCachedInheritedStyleDataOnDescendants(uint32_t aStructs);
+
+#ifdef DEBUG
+  void AssertStructsNotUsedElsewhere(nsStyleContext* aDestroyingContext,
+                                     int32_t aLevels) const;
+#endif
+
+#ifdef RESTYLE_LOGGING
+  void LogStyleContextTree(bool aFirst, uint32_t aStructs);
+
+  // This only gets called under call trees where we've already checked
+  // that PresContext()->RestyleManager()->ShouldLogRestyle() returned true.
+  // It exists here just to satisfy LOG_RESTYLE's expectations.
+  bool ShouldLogRestyle() { return true; }
+#endif
+
+  RefPtr<nsStyleContext> mParent;
+
+  // Children are kept in two circularly-linked lists.  The list anchor
+  // is not part of the list (null for empty), and we point to the first
+  // child.
+  // mEmptyChild for children whose rule node is the root rule node, and
+  // mChild for other children.  The order of children is not
+  // meaningful.
+  nsStyleContext* mChild;
+  nsStyleContext* mEmptyChild;
+  nsStyleContext* mPrevSibling;
+  nsStyleContext* mNextSibling;
+
+  // Style to be used instead for the R, G, and B components of color,
+  // background-color, and border-*-color if the nearest ancestor link
+  // element is visited (see RelevantLinkVisited()).
+  RefPtr<nsStyleContext> mStyleIfVisited;
+
+  // If this style context is for a pseudo-element or anonymous box,
+  // the relevant atom.
+  nsCOMPtr<nsIAtom> mPseudoTag;
+
+  // The source for our style data, either a Gecko nsRuleNode or a Servo
+  // ComputedValues struct. This never changes after construction, except
+  // when it's released and nulled out during teardown.
+  const mozilla::OwningStyleContextSource mSource;
+
+#ifdef MOZ_STYLO
+  // In Gecko, we can get this off the rule node. We make this conditional
+  // on stylo builds to avoid the memory bloat on release.
+  nsPresContext* mPresContext;
+#endif
+
+  // mCachedInheritedData and mCachedResetData point to both structs that
+  // are owned by this style context and structs that are owned by one of
+  // this style context's ancestors (which are indirectly owned since this
+  // style context owns a reference to its parent).  If the bit in |mBits|
+  // is set for a struct, that means that the pointer for that struct is
+  // owned by an ancestor or by the rule node rather than by this style context.
+  // Since style contexts typically have some inherited data but only sometimes
+  // have reset data, we always allocate the mCachedInheritedData, but only
+  // sometimes allocate the mCachedResetData.
+  nsResetStyleData*       mCachedResetData; // Cached reset style data.
+  nsInheritedStyleData    mCachedInheritedData; // Cached inherited style data
+
+  // mBits stores a number of things:
+  //  - It records (using the style struct bits) which structs are
+  //    inherited from the parent context or owned by the rule node (i.e.,
+  //    not owned by the style context).
+  //  - It also stores the additional bits listed at the top of
+  //    nsStyleStruct.h.
+  uint64_t                mBits;
+
+  uint32_t                mRefCnt;
+
+  // For now we store change hints on the style context during parallel traversal.
+  // We should improve this - see bug 1289861.
+#ifdef MOZ_STYLO
+  nsChangeHint            mStoredChangeHint;
+#ifdef DEBUG
+  bool                    mConsumedChangeHint;
+#endif
+#endif
+
+#ifdef DEBUG
+  uint32_t                mFrameRefCnt; // number of frames that use this
+                                        // as their style context
+
+  nsStyleStructID         mComputingStruct;
+
+  static bool DependencyAllowed(nsStyleStructID aOuterSID,
+                                nsStyleStructID aInnerSID)
+  {
+    return !!(sDependencyTable[aOuterSID] &
+              nsCachedStyleData::GetBitForSID(aInnerSID));
+  }
+
+  static const uint32_t sDependencyTable[];
+#endif
+};
+
+already_AddRefed<nsStyleContext>
+NS_NewStyleContext(nsStyleContext* aParentContext,
+                   nsIAtom* aPseudoTag,
+                   mozilla::CSSPseudoElementType aPseudoType,
+                   nsRuleNode* aRuleNode,
+                   bool aSkipParentDisplayBasedStyleFixup);
+
+already_AddRefed<nsStyleContext>
+NS_NewStyleContext(nsStyleContext* aParentContext,
+                   nsPresContext* aPresContext,
+                   nsIAtom* aPseudoTag,
+                   mozilla::CSSPseudoElementType aPseudoType,
+                   already_AddRefed<ServoComputedValues> aComputedValues,
+                   bool aSkipParentDisplayBasedStyleFixup);
+
+#endif