Add m-esr52 at 52.6.0

1 files changed, 1836 insertions, 0 deletions

diff --git a/layout/style/nsStyleContext.cpp b/layout/style/nsStyleContext.cpp
new file mode 100644
index 000000000..7ad260f1b
--- /dev/null
+++ b/layout/style/nsStyleContext.cpp
@@ -0,0 +1,1836 @@
+/* -*- 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 */
+
+#include "CSSVariableImageTable.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Maybe.h"
+
+#include "nsCSSAnonBoxes.h"
+#include "nsCSSPseudoElements.h"
+#include "nsStyleConsts.h"
+#include "nsString.h"
+#include "nsPresContext.h"
+#include "nsIStyleRule.h"
+
+#include "nsCOMPtr.h"
+#include "nsStyleSet.h"
+#include "nsIPresShell.h"
+
+#include "nsRuleNode.h"
+#include "nsStyleContext.h"
+#include "mozilla/StyleAnimationValue.h"
+#include "GeckoProfiler.h"
+#include "nsIDocument.h"
+#include "nsPrintfCString.h"
+#include "RubyUtils.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/ArenaObjectID.h"
+#include "mozilla/StyleSetHandle.h"
+#include "mozilla/StyleSetHandleInlines.h"
+
+#include "mozilla/ReflowInput.h"
+#include "nsLayoutUtils.h"
+#include "nsCoord.h"
+
+// Ensure the binding function declarations in nsStyleContext.h matches
+// those in ServoBindings.h.
+#include "mozilla/ServoBindings.h"
+
+using namespace mozilla;
+
+//----------------------------------------------------------------------
+
+#ifdef DEBUG
+
+// Check that the style struct IDs are in the same order as they are
+// in nsStyleStructList.h, since when we set up the IDs, we include
+// the inherited and reset structs spearately from nsStyleStructList.h
+enum DebugStyleStruct {
+#define STYLE_STRUCT(name, checkdata_cb) eDebugStyleStruct_##name,
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+};
+
+#define STYLE_STRUCT(name, checkdata_cb) \
+  static_assert(static_cast<int>(eDebugStyleStruct_##name) == \
+                  static_cast<int>(eStyleStruct_##name), \
+                "Style struct IDs are not declared in order?");
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+
+const uint32_t nsStyleContext::sDependencyTable[] = {
+#define STYLE_STRUCT(name, checkdata_cb)
+#define STYLE_STRUCT_DEP(dep) NS_STYLE_INHERIT_BIT(dep) |
+#define STYLE_STRUCT_END() 0,
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+#undef STYLE_STRUCT_DEP
+#undef STYLE_STRUCT_END
+};
+
+// Whether to perform expensive assertions in the nsStyleContext destructor.
+static bool sExpensiveStyleStructAssertionsEnabled;
+#endif
+
+nsStyleContext::nsStyleContext(nsStyleContext* aParent,
+                               OwningStyleContextSource&& aSource,
+                               nsIAtom* aPseudoTag,
+                               CSSPseudoElementType aPseudoType)
+  : mParent(aParent)
+  , mChild(nullptr)
+  , mEmptyChild(nullptr)
+  , mPseudoTag(aPseudoTag)
+  , mSource(Move(aSource))
+#ifdef MOZ_STYLO
+  , mPresContext(nullptr)
+#endif
+  , mCachedResetData(nullptr)
+  , mBits(((uint64_t)aPseudoType) << NS_STYLE_CONTEXT_TYPE_SHIFT)
+  , mRefCnt(0)
+#ifdef MOZ_STYLO
+  , mStoredChangeHint(nsChangeHint(0))
+#ifdef DEBUG
+  , mConsumedChangeHint(false)
+#endif
+#endif
+#ifdef DEBUG
+  , mFrameRefCnt(0)
+  , mComputingStruct(nsStyleStructID_None)
+#endif
+{
+  MOZ_COUNT_CTOR(nsStyleContext);
+}
+
+nsStyleContext::nsStyleContext(nsStyleContext* aParent,
+                               nsIAtom* aPseudoTag,
+                               CSSPseudoElementType aPseudoType,
+                               already_AddRefed<nsRuleNode> aRuleNode,
+                               bool aSkipParentDisplayBasedStyleFixup)
+  : nsStyleContext(aParent, OwningStyleContextSource(Move(aRuleNode)),
+                   aPseudoTag, aPseudoType)
+{
+#ifdef MOZ_STYLO
+  mPresContext = mSource.AsGeckoRuleNode()->PresContext();
+#endif
+
+  if (aParent) {
+#ifdef DEBUG
+    nsRuleNode *r1 = mParent->RuleNode(), *r2 = mSource.AsGeckoRuleNode();
+    while (r1->GetParent())
+      r1 = r1->GetParent();
+    while (r2->GetParent())
+      r2 = r2->GetParent();
+    NS_ASSERTION(r1 == r2, "must be in the same rule tree as parent");
+#endif
+  } else {
+    PresContext()->PresShell()->StyleSet()->RootStyleContextAdded();
+  }
+
+  mSource.AsGeckoRuleNode()->SetUsedDirectly(); // before ApplyStyleFixups()!
+  FinishConstruction(aSkipParentDisplayBasedStyleFixup);
+}
+
+nsStyleContext::nsStyleContext(nsStyleContext* aParent,
+                               nsPresContext* aPresContext,
+                               nsIAtom* aPseudoTag,
+                               CSSPseudoElementType aPseudoType,
+                               already_AddRefed<ServoComputedValues> aComputedValues,
+                               bool aSkipParentDisplayBasedStyleFixup)
+  : nsStyleContext(aParent, OwningStyleContextSource(Move(aComputedValues)),
+                   aPseudoTag, aPseudoType)
+{
+#ifdef MOZ_STYLO
+  mPresContext = aPresContext;
+#endif
+
+  FinishConstruction(aSkipParentDisplayBasedStyleFixup);
+}
+
+void
+nsStyleContext::FinishConstruction(bool aSkipParentDisplayBasedStyleFixup)
+{
+  // This check has to be done "backward", because if it were written the
+  // more natural way it wouldn't fail even when it needed to.
+  static_assert((UINT64_MAX >> NS_STYLE_CONTEXT_TYPE_SHIFT) >=
+                 static_cast<CSSPseudoElementTypeBase>(
+                   CSSPseudoElementType::MAX),
+                "pseudo element bits no longer fit in a uint64_t");
+  MOZ_ASSERT(!mSource.IsNull());
+
+#ifdef DEBUG
+  static_assert(MOZ_ARRAY_LENGTH(nsStyleContext::sDependencyTable)
+                  == nsStyleStructID_Length,
+                "Number of items in dependency table doesn't match IDs");
+#endif
+
+  mNextSibling = this;
+  mPrevSibling = this;
+  if (mParent) {
+    mParent->AddChild(this);
+  }
+
+  SetStyleBits();
+  if (!mSource.IsServoComputedValues()) {
+    ApplyStyleFixups(aSkipParentDisplayBasedStyleFixup);
+  }
+
+  #define eStyleStruct_LastItem (nsStyleStructID_Length - 1)
+  NS_ASSERTION(NS_STYLE_INHERIT_MASK & NS_STYLE_INHERIT_BIT(LastItem),
+               "NS_STYLE_INHERIT_MASK must be bigger, and other bits shifted");
+  #undef eStyleStruct_LastItem
+}
+
+nsStyleContext::~nsStyleContext()
+{
+  MOZ_COUNT_DTOR(nsStyleContext);
+  NS_ASSERTION((nullptr == mChild) && (nullptr == mEmptyChild), "destructing context with children");
+
+#ifdef DEBUG
+  if (sExpensiveStyleStructAssertionsEnabled) {
+    // Assert that the style structs we are about to destroy are not referenced
+    // anywhere else in the style context tree.  These checks are expensive,
+    // which is why they are not enabled by default.
+    nsStyleContext* root = this;
+    while (root->mParent) {
+      root = root->mParent;
+    }
+    root->AssertStructsNotUsedElsewhere(this,
+                                        std::numeric_limits<int32_t>::max());
+  } else {
+    // In DEBUG builds when the pref is not enabled, we perform a more limited
+    // check just of the children of this style context.
+    AssertStructsNotUsedElsewhere(this, 2);
+  }
+#endif
+
+  nsPresContext *presContext = PresContext();
+  DebugOnly<nsStyleSet*> geckoStyleSet = presContext->PresShell()->StyleSet()->GetAsGecko();
+  NS_ASSERTION(!geckoStyleSet ||
+               geckoStyleSet->GetRuleTree() == mSource.AsGeckoRuleNode()->RuleTree() ||
+               geckoStyleSet->IsInRuleTreeReconstruct(),
+               "destroying style context from old rule tree too late");
+
+  if (mParent) {
+    mParent->RemoveChild(this);
+  } else {
+    presContext->StyleSet()->RootStyleContextRemoved();
+  }
+
+  // Free up our data structs.
+  mCachedInheritedData.DestroyStructs(mBits, presContext);
+  if (mCachedResetData) {
+    mCachedResetData->Destroy(mBits, presContext);
+  }
+
+  // Free any ImageValues we were holding on to for CSS variable values.
+  CSSVariableImageTable::RemoveAll(this);
+}
+
+#ifdef DEBUG
+void
+nsStyleContext::AssertStructsNotUsedElsewhere(
+                                       nsStyleContext* aDestroyingContext,
+                                       int32_t aLevels) const
+{
+  if (aLevels == 0) {
+    return;
+  }
+
+  void* data;
+
+  if (mBits & NS_STYLE_IS_GOING_AWAY) {
+    return;
+  }
+
+  if (this != aDestroyingContext) {
+    nsInheritedStyleData& destroyingInheritedData =
+      aDestroyingContext->mCachedInheritedData;
+#define STYLE_STRUCT_INHERITED(name_, checkdata_cb)                            \
+    data = destroyingInheritedData.mStyleStructs[eStyleStruct_##name_];        \
+    if (data &&                                                                \
+        !(aDestroyingContext->mBits & NS_STYLE_INHERIT_BIT(name_)) &&          \
+         (mCachedInheritedData.mStyleStructs[eStyleStruct_##name_] == data)) { \
+      printf_stderr("style struct %p found on style context %p\n", data, this);\
+      nsString url;                                                            \
+      nsresult rv = PresContext()->Document()->GetURL(url);                    \
+      if (NS_SUCCEEDED(rv)) {                                                  \
+        printf_stderr("  in %s\n", NS_ConvertUTF16toUTF8(url).get());          \
+      }                                                                        \
+      MOZ_ASSERT(false, "destroying " #name_ " style struct still present "    \
+                        "in style context tree");                              \
+    }
+#define STYLE_STRUCT_RESET(name_, checkdata_cb)
+
+#include "nsStyleStructList.h"
+
+#undef STYLE_STRUCT_INHERITED
+#undef STYLE_STRUCT_RESET
+
+    if (mCachedResetData) {
+      nsResetStyleData* destroyingResetData =
+        aDestroyingContext->mCachedResetData;
+      if (destroyingResetData) {
+#define STYLE_STRUCT_INHERITED(name_, checkdata_cb_)
+#define STYLE_STRUCT_RESET(name_, checkdata_cb)                                \
+        data = destroyingResetData->mStyleStructs[eStyleStruct_##name_];       \
+        if (data &&                                                            \
+            !(aDestroyingContext->mBits & NS_STYLE_INHERIT_BIT(name_)) &&      \
+            (mCachedResetData->mStyleStructs[eStyleStruct_##name_] == data)) { \
+          printf_stderr("style struct %p found on style context %p\n", data,   \
+                        this);                                                 \
+          nsString url;                                                        \
+          nsresult rv = PresContext()->Document()->GetURL(url);                \
+          if (NS_SUCCEEDED(rv)) {                                              \
+            printf_stderr("  in %s\n", NS_ConvertUTF16toUTF8(url).get());      \
+          }                                                                    \
+          MOZ_ASSERT(false, "destroying " #name_ " style struct still present "\
+                            "in style context tree");                          \
+        }
+
+#include "nsStyleStructList.h"
+
+#undef STYLE_STRUCT_INHERITED
+#undef STYLE_STRUCT_RESET
+      }
+    }
+  }
+
+  if (mChild) {
+    const nsStyleContext* child = mChild;
+    do {
+      child->AssertStructsNotUsedElsewhere(aDestroyingContext, aLevels - 1);
+      child = child->mNextSibling;
+    } while (child != mChild);
+  }
+
+  if (mEmptyChild) {
+    const nsStyleContext* child = mEmptyChild;
+    do {
+      child->AssertStructsNotUsedElsewhere(aDestroyingContext, aLevels - 1);
+      child = child->mNextSibling;
+    } while (child != mEmptyChild);
+  }
+}
+#endif
+
+void nsStyleContext::AddChild(nsStyleContext* aChild)
+{
+  NS_ASSERTION(aChild->mPrevSibling == aChild &&
+               aChild->mNextSibling == aChild,
+               "child already in a child list");
+
+  nsStyleContext **listPtr = aChild->mSource.MatchesNoRules() ? &mEmptyChild : &mChild;
+  // Explicitly dereference listPtr so that compiler doesn't have to know that mNextSibling
+  // etc. don't alias with what ever listPtr points at.
+  nsStyleContext *list = *listPtr;
+
+  // Insert at the beginning of the list.  See also FindChildWithRules.
+  if (list) {
+    // Link into existing elements, if there are any.
+    aChild->mNextSibling = list;
+    aChild->mPrevSibling = list->mPrevSibling;
+    list->mPrevSibling->mNextSibling = aChild;
+    list->mPrevSibling = aChild;
+  }
+  (*listPtr) = aChild;
+}
+
+void nsStyleContext::RemoveChild(nsStyleContext* aChild)
+{
+  NS_PRECONDITION(nullptr != aChild && this == aChild->mParent, "bad argument");
+
+  nsStyleContext **list = aChild->mSource.MatchesNoRules() ? &mEmptyChild : &mChild;
+
+  if (aChild->mPrevSibling != aChild) { // has siblings
+    if ((*list) == aChild) {
+      (*list) = (*list)->mNextSibling;
+    }
+  }
+  else {
+    NS_ASSERTION((*list) == aChild, "bad sibling pointers");
+    (*list) = nullptr;
+  }
+
+  aChild->mPrevSibling->mNextSibling = aChild->mNextSibling;
+  aChild->mNextSibling->mPrevSibling = aChild->mPrevSibling;
+  aChild->mNextSibling = aChild;
+  aChild->mPrevSibling = aChild;
+}
+
+void
+nsStyleContext::MoveTo(nsStyleContext* aNewParent)
+{
+  MOZ_ASSERT(aNewParent != mParent);
+
+  // This function shouldn't be getting called if the parents have different
+  // values for some flags in mBits (unless the flag is also set on this style
+  // context) because if that were the case we would need to recompute those
+  // bits for |this|.
+
+#define CHECK_FLAG(bit_) \
+  MOZ_ASSERT((mParent->mBits & (bit_)) == (aNewParent->mBits & (bit_)) ||     \
+             (mBits & (bit_)),                                                \
+             "MoveTo cannot be called if " #bit_ " value on old and new "     \
+             "style context parents do not match, unless the flag is set "    \
+             "on this style context");
+
+  CHECK_FLAG(NS_STYLE_HAS_PSEUDO_ELEMENT_DATA)
+  CHECK_FLAG(NS_STYLE_IN_DISPLAY_NONE_SUBTREE)
+  CHECK_FLAG(NS_STYLE_HAS_TEXT_DECORATION_LINES)
+  CHECK_FLAG(NS_STYLE_RELEVANT_LINK_VISITED)
+
+#undef CHECK_FLAG
+
+  // Assertions checking for visited style are just to avoid some tricky
+  // cases we can't be bothered handling at the moment.
+  MOZ_ASSERT(!IsStyleIfVisited());
+  MOZ_ASSERT(!mParent->IsStyleIfVisited());
+  MOZ_ASSERT(!aNewParent->IsStyleIfVisited());
+  MOZ_ASSERT(!mStyleIfVisited || mStyleIfVisited->mParent == mParent);
+
+  if (mParent->HasChildThatUsesResetStyle()) {
+    aNewParent->AddStyleBit(NS_STYLE_HAS_CHILD_THAT_USES_RESET_STYLE);
+  }
+
+  mParent->RemoveChild(this);
+  mParent = aNewParent;
+  mParent->AddChild(this);
+
+  if (mStyleIfVisited) {
+    mStyleIfVisited->mParent->RemoveChild(mStyleIfVisited);
+    mStyleIfVisited->mParent = aNewParent;
+    mStyleIfVisited->mParent->AddChild(mStyleIfVisited);
+  }
+}
+
+already_AddRefed<nsStyleContext>
+nsStyleContext::FindChildWithRules(const nsIAtom* aPseudoTag,
+                                   NonOwningStyleContextSource aSource,
+                                   NonOwningStyleContextSource aSourceIfVisited,
+                                   bool aRelevantLinkVisited)
+{
+  uint32_t threshold = 10; // The # of siblings we're willing to examine
+                           // before just giving this whole thing up.
+
+  RefPtr<nsStyleContext> result;
+  nsStyleContext *list = aSource.MatchesNoRules() ? mEmptyChild : mChild;
+
+  if (list) {
+    nsStyleContext *child = list;
+    do {
+      if (child->mSource.AsRaw() == aSource &&
+          child->mPseudoTag == aPseudoTag &&
+          !child->IsStyleIfVisited() &&
+          child->RelevantLinkVisited() == aRelevantLinkVisited) {
+        bool match = false;
+        if (!aSourceIfVisited.IsNull()) {
+          match = child->GetStyleIfVisited() &&
+                  child->GetStyleIfVisited()->mSource.AsRaw() == aSourceIfVisited;
+        } else {
+          match = !child->GetStyleIfVisited();
+        }
+        if (match && !(child->mBits & NS_STYLE_INELIGIBLE_FOR_SHARING)) {
+          result = child;
+          break;
+        }
+      }
+      child = child->mNextSibling;
+      threshold--;
+      if (threshold == 0)
+        break;
+    } while (child != list);
+  }
+
+  if (result) {
+    if (result != list) {
+      // Move result to the front of the list.
+      RemoveChild(result);
+      AddChild(result);
+    }
+    result->mBits |= NS_STYLE_IS_SHARED;
+  }
+
+  return result.forget();
+}
+
+const void* nsStyleContext::StyleData(nsStyleStructID aSID)
+{
+  const void* cachedData = GetCachedStyleData(aSID);
+  if (cachedData)
+    return cachedData; // We have computed data stored on this node in the context tree.
+  // Our style source will take care of it for us.
+  const void* newData;
+  if (mSource.IsGeckoRuleNode()) {
+    newData = mSource.AsGeckoRuleNode()->GetStyleData(aSID, this, true);
+    if (!nsCachedStyleData::IsReset(aSID)) {
+      // always cache inherited data on the style context; the rule
+      // node set the bit in mBits for us if needed.
+      mCachedInheritedData.mStyleStructs[aSID] = const_cast<void*>(newData);
+    }
+  } else {
+    newData = StyleStructFromServoComputedValues(aSID);
+
+    // perform any remaining main thread work on the struct
+    switch (aSID) {
+#define STYLE_STRUCT(name_, checkdata_cb_)                                    \
+      case eStyleStruct_##name_: {                                            \
+        auto data = static_cast<const nsStyle##name_*>(newData);              \
+        const_cast<nsStyle##name_*>(data)->FinishStyle(PresContext());        \
+        break;                                                                \
+      }
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+      default:
+        MOZ_ASSERT_UNREACHABLE("unexpected nsStyleStructID value");
+        break;
+    }
+
+    // The Servo-backed StyleContextSource owns the struct.
+    AddStyleBit(nsCachedStyleData::GetBitForSID(aSID));
+
+    // 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 the struct getters in nsStyleContext.h.
+    SetStyle(aSID, const_cast<void*>(newData));
+  }
+  return newData;
+}
+
+// This is an evil evil function, since it forces you to alloc your own separate copy of
+// style data!  Do not use this function unless you absolutely have to!  You should avoid
+// this at all costs! -dwh
+void*
+nsStyleContext::GetUniqueStyleData(const nsStyleStructID& aSID)
+{
+  MOZ_ASSERT(!mSource.IsServoComputedValues(),
+             "Can't COW-mutate servo values from Gecko!");
+
+  // If we already own the struct and no kids could depend on it, then
+  // just return it.  (We leak in this case if there are kids -- and this
+  // function really shouldn't be called for style contexts that could
+  // have kids depending on the data.  ClearStyleData would be OK, but
+  // this test for no mChild or mEmptyChild doesn't catch that case.)
+  const void *current = StyleData(aSID);
+  if (!mChild && !mEmptyChild &&
+      !(mBits & nsCachedStyleData::GetBitForSID(aSID)) &&
+      GetCachedStyleData(aSID))
+    return const_cast<void*>(current);
+
+  void* result;
+  nsPresContext *presContext = PresContext();
+  switch (aSID) {
+
+#define UNIQUE_CASE(c_)                                                       \
+  case eStyleStruct_##c_:                                                     \
+    result = new (presContext) nsStyle##c_(                                   \
+      * static_cast<const nsStyle##c_ *>(current));                           \
+    break;
+
+  UNIQUE_CASE(Font)
+  UNIQUE_CASE(Display)
+  UNIQUE_CASE(Text)
+  UNIQUE_CASE(TextReset)
+  UNIQUE_CASE(Visibility)
+
+#undef UNIQUE_CASE
+
+  default:
+    NS_ERROR("Struct type not supported.  Please find another way to do this if you can!");
+    return nullptr;
+  }
+
+  SetStyle(aSID, result);
+  mBits &= ~static_cast<uint64_t>(nsCachedStyleData::GetBitForSID(aSID));
+
+  return result;
+}
+
+// This is an evil function, but less evil than GetUniqueStyleData. It
+// creates an empty style struct for this nsStyleContext.
+void*
+nsStyleContext::CreateEmptyStyleData(const nsStyleStructID& aSID)
+{
+  MOZ_ASSERT(!mChild && !mEmptyChild &&
+             !(mBits & nsCachedStyleData::GetBitForSID(aSID)) &&
+             !GetCachedStyleData(aSID),
+             "This style should not have been computed");
+
+  void* result;
+  nsPresContext* presContext = PresContext();
+  switch (aSID) {
+#define UNIQUE_CASE(c_) \
+    case eStyleStruct_##c_: \
+      result = new (presContext) nsStyle##c_(presContext); \
+      break;
+
+  UNIQUE_CASE(Border)
+  UNIQUE_CASE(Padding)
+
+#undef UNIQUE_CASE
+
+  default:
+    NS_ERROR("Struct type not supported.");
+    return nullptr;
+  }
+
+  // The new struct is owned by this style context, but that we don't
+  // need to clear the bit in mBits because we've asserted that at the
+  // top of this function.
+  SetStyle(aSID, result);
+  return result;
+}
+
+void
+nsStyleContext::SetStyle(nsStyleStructID aSID, void* aStruct)
+{
+  // This method should only be called from nsRuleNode!  It is not a public
+  // method!
+
+  NS_ASSERTION(aSID >= 0 && aSID < nsStyleStructID_Length, "out of bounds");
+
+  // NOTE:  nsCachedStyleData::GetStyleData works roughly the same way.
+  // See the comments there (in nsRuleNode.h) for more details about
+  // what this is doing and why.
+
+  void** dataSlot;
+  if (nsCachedStyleData::IsReset(aSID)) {
+    if (!mCachedResetData) {
+      mCachedResetData = new (PresContext()) nsResetStyleData;
+    }
+    dataSlot = &mCachedResetData->mStyleStructs[aSID];
+  } else {
+    dataSlot = &mCachedInheritedData.mStyleStructs[aSID];
+  }
+  NS_ASSERTION(!*dataSlot || (mBits & nsCachedStyleData::GetBitForSID(aSID)),
+               "Going to leak style data");
+  *dataSlot = aStruct;
+}
+
+static bool
+ShouldSuppressLineBreak(const nsStyleContext* aContext,
+                        const nsStyleDisplay* aDisplay,
+                        const nsStyleContext* aParentContext,
+                        const nsStyleDisplay* aParentDisplay)
+{
+  // The display change should only occur for "in-flow" children
+  if (aDisplay->IsOutOfFlowStyle()) {
+    return false;
+  }
+  // Display value of any anonymous box should not be touched. In most
+  // cases, anonymous boxes are actually not in ruby frame, but instead,
+  // some other frame with a ruby display value. Non-element pseudos
+  // which represents text frames, as well as ruby pseudos are excluded
+  // because we still want to set the flag for them.
+  if (aContext->GetPseudoType() == CSSPseudoElementType::AnonBox &&
+      !nsCSSAnonBoxes::IsNonElement(aContext->GetPseudo()) &&
+      !RubyUtils::IsRubyPseudo(aContext->GetPseudo())) {
+    return false;
+  }
+  if (aParentContext->ShouldSuppressLineBreak()) {
+    // Line break suppressing bit is propagated to any children of
+    // line participants, which include inline, contents, and inline
+    // ruby boxes.
+    if (aParentDisplay->mDisplay == mozilla::StyleDisplay::Inline ||
+        aParentDisplay->mDisplay == mozilla::StyleDisplay::Contents ||
+        aParentDisplay->mDisplay == mozilla::StyleDisplay::Ruby ||
+        aParentDisplay->mDisplay == mozilla::StyleDisplay::RubyBaseContainer) {
+      return true;
+    }
+  }
+  // Any descendant of ruby level containers is non-breakable, but
+  // the level containers themselves are breakable. We have to check
+  // the container display type against all ruby display type here
+  // because any of the ruby boxes could be anonymous.
+  // Note that, when certain HTML tags, e.g. form controls, have ruby
+  // level container display type, they could also escape from this flag
+  // while they shouldn't. However, it is generally fine since they
+  // won't usually break the assertion that there is no line break
+  // inside ruby, because:
+  // 1. their display types, the ruby level container types, are inline-
+  //    outside, which means they won't cause any forced line break; and
+  // 2. they never start an inline span, which means their children, if
+  //    any, won't be able to break the line its ruby ancestor lays; and
+  // 3. their parent frame is always a ruby content frame (due to
+  //    anonymous ruby box generation), which makes line layout suppress
+  //    any optional line break around this frame.
+  // However, there is one special case which is BR tag, because it
+  // directly affects the line layout. This case is handled by the BR
+  // frame which checks the flag of its parent frame instead of itself.
+  if ((aParentDisplay->IsRubyDisplayType() &&
+       aDisplay->mDisplay != mozilla::StyleDisplay::RubyBaseContainer &&
+       aDisplay->mDisplay != mozilla::StyleDisplay::RubyTextContainer) ||
+      // Since ruby base and ruby text may exist themselves without any
+      // non-anonymous frame outside, we should also check them.
+      aDisplay->mDisplay == mozilla::StyleDisplay::RubyBase ||
+      aDisplay->mDisplay == mozilla::StyleDisplay::RubyText) {
+    return true;
+  }
+  return false;
+}
+
+// Flex & grid containers blockify their children.
+//  "The display value of a flex item is blockified"
+//    https://drafts.csswg.org/css-flexbox-1/#flex-items
+//  "The display value of a grid item is blockified"
+//    https://drafts.csswg.org/css-grid/#grid-items
+static bool
+ShouldBlockifyChildren(const nsStyleDisplay* aStyleDisp)
+{
+  auto displayVal = aStyleDisp->mDisplay;
+  return mozilla::StyleDisplay::Flex == displayVal ||
+    mozilla::StyleDisplay::InlineFlex == displayVal ||
+    mozilla::StyleDisplay::Grid == displayVal ||
+    mozilla::StyleDisplay::InlineGrid == displayVal;
+}
+
+void
+nsStyleContext::SetStyleBits()
+{
+  // XXXbholley: We should get this information directly from the
+  // ServoComputedValues rather than computing it here. This setup for
+  // ServoComputedValues-backed nsStyleContexts is probably not something
+  // we should ship.
+  //
+  // For example, NS_STYLE_IS_TEXT_COMBINED is still set in ApplyStyleFixups,
+  // which isn't called for ServoComputedValues.
+
+  // See if we have any text decorations.
+  // First see if our parent has text decorations.  If our parent does, then we inherit the bit.
+  if (mParent && mParent->HasTextDecorationLines()) {
+    mBits |= NS_STYLE_HAS_TEXT_DECORATION_LINES;
+  } else {
+    // We might have defined a decoration.
+    if (StyleTextReset()->HasTextDecorationLines()) {
+      mBits |= NS_STYLE_HAS_TEXT_DECORATION_LINES;
+    }
+  }
+
+  if ((mParent && mParent->HasPseudoElementData()) || IsPseudoElement()) {
+    mBits |= NS_STYLE_HAS_PSEUDO_ELEMENT_DATA;
+  }
+
+  // Set the NS_STYLE_IN_DISPLAY_NONE_SUBTREE bit
+  const nsStyleDisplay* disp = StyleDisplay();
+  if ((mParent && mParent->IsInDisplayNoneSubtree()) ||
+      disp->mDisplay == mozilla::StyleDisplay::None) {
+    mBits |= NS_STYLE_IN_DISPLAY_NONE_SUBTREE;
+  }
+}
+
+void
+nsStyleContext::ApplyStyleFixups(bool aSkipParentDisplayBasedStyleFixup)
+{
+  MOZ_ASSERT(!mSource.IsServoComputedValues(),
+             "Can't do Gecko style fixups on Servo values");
+
+#define GET_UNIQUE_STYLE_DATA(name_) \
+  static_cast<nsStyle##name_*>(GetUniqueStyleData(eStyleStruct_##name_))
+
+  // CSS Inline Layout Level 3 - 3.5 Sizing Initial Letters:
+  // For an N-line drop initial in a Western script, the cap-height of the
+  // letter needs to be (N – 1) times the line-height, plus the cap-height
+  // of the surrounding text.
+  if (mPseudoTag == nsCSSPseudoElements::firstLetter) {
+    const nsStyleTextReset* textReset = StyleTextReset();
+    if (textReset->mInitialLetterSize != 0.0f) {
+      nsStyleContext* containerSC = mParent;
+      const nsStyleDisplay* containerDisp = containerSC->StyleDisplay();
+      while (containerDisp->mDisplay == mozilla::StyleDisplay::Contents) {
+        if (!containerSC->GetParent()) {
+          break;
+        }
+        containerSC = containerSC->GetParent();
+        containerDisp = containerSC->StyleDisplay();
+      }
+      nscoord containerLH =
+        ReflowInput::CalcLineHeight(nullptr, containerSC, NS_AUTOHEIGHT, 1.0f);
+      RefPtr<nsFontMetrics> containerFM =
+        nsLayoutUtils::GetFontMetricsForStyleContext(containerSC);
+      MOZ_ASSERT(containerFM, "Should have fontMetrics!!");
+      nscoord containerCH = containerFM->CapHeight();
+      RefPtr<nsFontMetrics> firstLetterFM =
+        nsLayoutUtils::GetFontMetricsForStyleContext(this);
+      MOZ_ASSERT(firstLetterFM, "Should have fontMetrics!!");
+      nscoord firstLetterCH = firstLetterFM->CapHeight();
+      nsStyleFont* mutableStyleFont = GET_UNIQUE_STYLE_DATA(Font);
+      float invCapHeightRatio =
+        mutableStyleFont->mFont.size / NSCoordToFloat(firstLetterCH);
+      mutableStyleFont->mFont.size =
+        NSToCoordRound(((textReset->mInitialLetterSize - 1) * containerLH +
+                        containerCH) *
+                       invCapHeightRatio);
+    }
+  }
+
+  // Change writing mode of text frame for text-combine-upright. We use
+  // style structs of the parent to avoid triggering computation before
+  // we change the writing mode.
+  // It is safe to look at the parent's style because we are looking at
+  // inherited properties, and ::-moz-text never matches any rules.
+  if (mPseudoTag == nsCSSAnonBoxes::mozText && mParent &&
+      mParent->StyleVisibility()->mWritingMode !=
+        NS_STYLE_WRITING_MODE_HORIZONTAL_TB &&
+      mParent->StyleText()->mTextCombineUpright ==
+        NS_STYLE_TEXT_COMBINE_UPRIGHT_ALL) {
+    MOZ_ASSERT(!PeekStyleVisibility(), "If StyleVisibility was already "
+               "computed, some properties may have been computed "
+               "incorrectly based on the old writing mode value");
+    nsStyleVisibility* mutableVis = GET_UNIQUE_STYLE_DATA(Visibility);
+    mutableVis->mWritingMode = NS_STYLE_WRITING_MODE_HORIZONTAL_TB;
+    AddStyleBit(NS_STYLE_IS_TEXT_COMBINED);
+  }
+
+  // CSS 2.1 10.1: Propagate the root element's 'direction' to the ICB.
+  // (PageContentFrame/CanvasFrame etc will inherit 'direction')
+  if (mPseudoTag == nsCSSAnonBoxes::viewport) {
+    nsPresContext* presContext = PresContext();
+    mozilla::dom::Element* docElement = presContext->Document()->GetRootElement();
+    if (docElement) {
+      RefPtr<nsStyleContext> rootStyle =
+        presContext->StyleSet()->ResolveStyleFor(docElement, nullptr);
+      auto dir = rootStyle->StyleVisibility()->mDirection;
+      if (dir != StyleVisibility()->mDirection) {
+        nsStyleVisibility* uniqueVisibility = GET_UNIQUE_STYLE_DATA(Visibility);
+        uniqueVisibility->mDirection = dir;
+      }
+    }
+  }
+
+  // Correct tables.
+  const nsStyleDisplay* disp = StyleDisplay();
+  if (disp->mDisplay == mozilla::StyleDisplay::Table) {
+    // -moz-center and -moz-right are used for HTML's alignment
+    // This is covering the <div align="right"><table>...</table></div> case.
+    // In this case, we don't want to inherit the text alignment into the table.
+    const nsStyleText* text = StyleText();
+
+    if (text->mTextAlign == NS_STYLE_TEXT_ALIGN_MOZ_LEFT ||
+        text->mTextAlign == NS_STYLE_TEXT_ALIGN_MOZ_CENTER ||
+        text->mTextAlign == NS_STYLE_TEXT_ALIGN_MOZ_RIGHT)
+    {
+      nsStyleText* uniqueText = GET_UNIQUE_STYLE_DATA(Text);
+      uniqueText->mTextAlign = NS_STYLE_TEXT_ALIGN_START;
+    }
+  }
+
+  // CSS2.1 section 9.2.4 specifies fixups for the 'display' property of
+  // the root element.  We can't implement them in nsRuleNode because we
+  // don't want to store all display structs that aren't 'block',
+  // 'inline', or 'table' in the style context tree on the off chance
+  // that the root element has its style reresolved later.  So do them
+  // here if needed, by changing the style data, so that other code
+  // doesn't get confused by looking at the style data.
+  if (!mParent) {
+    auto displayVal = disp->mDisplay;
+    if (displayVal != mozilla::StyleDisplay::Contents) {
+      nsRuleNode::EnsureBlockDisplay(displayVal, true);
+    } else {
+      // http://dev.w3.org/csswg/css-display/#transformations
+      // "... a display-outside of 'contents' computes to block-level
+      //  on the root element."
+      displayVal = mozilla::StyleDisplay::Block;
+    }
+    if (displayVal != disp->mDisplay) {
+      nsStyleDisplay* mutable_display = GET_UNIQUE_STYLE_DATA(Display);
+      disp = mutable_display;
+
+      // If we're in this code, then mOriginalDisplay doesn't matter
+      // for purposes of the cascade (because this nsStyleDisplay
+      // isn't living in the ruletree anyway), and for determining
+      // hypothetical boxes it's better to have mOriginalDisplay
+      // matching mDisplay here.
+      mutable_display->mOriginalDisplay = mutable_display->mDisplay =
+        displayVal;
+    }
+  }
+
+  // Adjust the "display" values of flex and grid items (but not for raw text
+  // or placeholders). CSS3 Flexbox section 4 says:
+  //   # The computed 'display' of a flex item is determined
+  //   # by applying the table in CSS 2.1 Chapter 9.7.
+  // ...which converts inline-level elements to their block-level equivalents.
+  // Any block-level element directly contained by elements with ruby display
+  // values are converted to their inline-level equivalents.
+  if (!aSkipParentDisplayBasedStyleFixup && mParent) {
+    // Skip display:contents ancestors to reach the potential container.
+    // (If there are only display:contents ancestors between this node and
+    // a flex/grid container ancestor, then this node is a flex/grid item, since
+    // its parent *in the frame tree* will be the flex/grid container. So we treat
+    // it like a flex/grid item here.)
+    nsStyleContext* containerContext = mParent;
+    const nsStyleDisplay* containerDisp = containerContext->StyleDisplay();
+    while (containerDisp->mDisplay == mozilla::StyleDisplay::Contents) {
+      if (!containerContext->GetParent()) {
+        break;
+      }
+      containerContext = containerContext->GetParent();
+      containerDisp = containerContext->StyleDisplay();
+    }
+    if (ShouldBlockifyChildren(containerDisp) &&
+        !nsCSSAnonBoxes::IsNonElement(GetPseudo())) {
+      // NOTE: Technically, we shouldn't modify the 'display' value of
+      // positioned elements, since they aren't flex/grid items. However,
+      // we don't need to worry about checking for that, because if we're
+      // positioned, we'll have already been through a call to
+      // EnsureBlockDisplay() in nsRuleNode, so this call here won't change
+      // anything. So we're OK.
+      auto displayVal = disp->mDisplay;
+      nsRuleNode::EnsureBlockDisplay(displayVal);
+      if (displayVal != disp->mDisplay) {
+        NS_ASSERTION(!disp->IsAbsolutelyPositionedStyle(),
+                     "We shouldn't be changing the display value of "
+                     "positioned content (and we should have already "
+                     "converted its display value to be block-level...)");
+        nsStyleDisplay* mutable_display = GET_UNIQUE_STYLE_DATA(Display);
+        disp = mutable_display;
+        mutable_display->mDisplay = displayVal;
+      }
+    }
+  }
+
+  // Note: This must come after the blockification above, otherwise we fail
+  // the grid-item-blockifying-001.html reftest.
+  if (mParent && ::ShouldSuppressLineBreak(this, disp, mParent,
+                                           mParent->StyleDisplay())) {
+    mBits |= NS_STYLE_SUPPRESS_LINEBREAK;
+    auto displayVal = disp->mDisplay;
+    nsRuleNode::EnsureInlineDisplay(displayVal);
+    if (displayVal != disp->mDisplay) {
+      nsStyleDisplay* mutable_display = GET_UNIQUE_STYLE_DATA(Display);
+      disp = mutable_display;
+      mutable_display->mDisplay = displayVal;
+    }
+  }
+  // Suppress border/padding of ruby level containers
+  if (disp->mDisplay == mozilla::StyleDisplay::RubyBaseContainer ||
+      disp->mDisplay == mozilla::StyleDisplay::RubyTextContainer) {
+    CreateEmptyStyleData(eStyleStruct_Border);
+    CreateEmptyStyleData(eStyleStruct_Padding);
+  }
+  if (disp->IsRubyDisplayType()) {
+    // Per CSS Ruby spec section Bidi Reordering, for all ruby boxes,
+    // the 'normal' and 'embed' values of 'unicode-bidi' should compute to
+    // 'isolate', and 'bidi-override' should compute to 'isolate-override'.
+    const nsStyleTextReset* textReset = StyleTextReset();
+    uint8_t unicodeBidi = textReset->mUnicodeBidi;
+    if (unicodeBidi == NS_STYLE_UNICODE_BIDI_NORMAL ||
+        unicodeBidi == NS_STYLE_UNICODE_BIDI_EMBED) {
+      unicodeBidi = NS_STYLE_UNICODE_BIDI_ISOLATE;
+    } else if (unicodeBidi == NS_STYLE_UNICODE_BIDI_BIDI_OVERRIDE) {
+      unicodeBidi = NS_STYLE_UNICODE_BIDI_ISOLATE_OVERRIDE;
+    }
+    if (unicodeBidi != textReset->mUnicodeBidi) {
+      nsStyleTextReset* mutableTextReset = GET_UNIQUE_STYLE_DATA(TextReset);
+      mutableTextReset->mUnicodeBidi = unicodeBidi;
+    }
+  }
+
+  /*
+   * According to https://drafts.csswg.org/css-writing-modes-3/#block-flow:
+   *
+   * If a box has a different block flow direction than its containing block:
+   *   * If the box has a specified display of inline, its display computes
+   *     to inline-block. [CSS21]
+   *   ...etc.
+   */
+  if (disp->mDisplay == mozilla::StyleDisplay::Inline &&
+      !nsCSSAnonBoxes::IsNonElement(mPseudoTag) &&
+      mParent) {
+    auto cbContext = mParent;
+    while (cbContext->StyleDisplay()->mDisplay == mozilla::StyleDisplay::Contents) {
+      cbContext = cbContext->mParent;
+    }
+    MOZ_ASSERT(cbContext, "the root context can't have display:contents");
+    // We don't need the full mozilla::WritingMode value (incorporating dir
+    // and text-orientation) here; just the writing-mode property is enough.
+    if (StyleVisibility()->mWritingMode !=
+          cbContext->StyleVisibility()->mWritingMode) {
+      nsStyleDisplay* mutable_display = GET_UNIQUE_STYLE_DATA(Display);
+      disp = mutable_display;
+      mutable_display->mOriginalDisplay = mutable_display->mDisplay =
+        mozilla::StyleDisplay::InlineBlock;
+    }
+  }
+
+  // Compute User Interface style, to trigger loads of cursors
+  StyleUserInterface();
+#undef GET_UNIQUE_STYLE_DATA
+}
+
+template<class StyleContextLike>
+nsChangeHint
+nsStyleContext::CalcStyleDifferenceInternal(StyleContextLike* aNewContext,
+                                            nsChangeHint aParentHintsNotHandledForDescendants,
+                                            uint32_t* aEqualStructs,
+                                            uint32_t* aSamePointerStructs)
+{
+  PROFILER_LABEL("nsStyleContext", "CalcStyleDifference",
+    js::ProfileEntry::Category::CSS);
+
+  MOZ_ASSERT(NS_IsHintSubset(aParentHintsNotHandledForDescendants,
+                             nsChangeHint_Hints_NotHandledForDescendants),
+             "caller is passing inherited hints, but shouldn't be");
+
+  static_assert(nsStyleStructID_Length <= 32,
+                "aEqualStructs is not big enough");
+
+  *aEqualStructs = 0;
+
+  nsChangeHint hint = nsChangeHint(0);
+  NS_ENSURE_TRUE(aNewContext, hint);
+  // We must always ensure that we populate the structs on the new style
+  // context that are filled in on the old context, so that if we get
+  // two style changes in succession, the second of which causes a real
+  // style change, the PeekStyleData doesn't return null (implying that
+  // nobody ever looked at that struct's data).  In other words, we
+  // can't skip later structs if we get a big change up front, because
+  // we could later get a small change in one of those structs that we
+  // don't want to miss.
+
+  // If our sources are the same, then any differences in style data
+  // are already accounted for by differences on ancestors.  We know
+  // this because CalcStyleDifference is always called on two style
+  // contexts that point to the same element, so we know that our
+  // position in the style context tree is the same and our position in
+  // the rule node tree (if applicable) is also the same.
+  // However, if there were noninherited style change hints on the
+  // parent, we might produce these same noninherited hints on this
+  // style context's frame due to 'inherit' values, so we do need to
+  // compare.
+  // (Things like 'em' units are handled by the change hint produced
+  // by font-size changing, so we don't need to worry about them like
+  // we worry about 'inherit' values.)
+  bool compare = StyleSource() != aNewContext->StyleSource();
+
+  DebugOnly<uint32_t> structsFound = 0;
+
+  // If we had any change in variable values, then we'll need to examine
+  // all of the other style structs too, even if the new style context has
+  // the same source as the old one.
+  const nsStyleVariables* thisVariables = PeekStyleVariables();
+  if (thisVariables) {
+    structsFound |= NS_STYLE_INHERIT_BIT(Variables);
+    const nsStyleVariables* otherVariables = aNewContext->StyleVariables();
+    if (thisVariables->mVariables == otherVariables->mVariables) {
+      *aEqualStructs |= NS_STYLE_INHERIT_BIT(Variables);
+    } else {
+      compare = true;
+    }
+  } else {
+    *aEqualStructs |= NS_STYLE_INHERIT_BIT(Variables);
+  }
+
+  DebugOnly<int> styleStructCount = 1;  // count Variables already
+
+#define DO_STRUCT_DIFFERENCE(struct_)                                         \
+  PR_BEGIN_MACRO                                                              \
+    const nsStyle##struct_* this##struct_ = PeekStyle##struct_();             \
+    if (this##struct_) {                                                      \
+      structsFound |= NS_STYLE_INHERIT_BIT(struct_);                          \
+      const nsStyle##struct_* other##struct_ = aNewContext->Style##struct_(); \
+      nsChangeHint maxDifference = nsStyle##struct_::MaxDifference();         \
+      nsChangeHint differenceAlwaysHandledForDescendants =                    \
+        nsStyle##struct_::DifferenceAlwaysHandledForDescendants();            \
+      if (this##struct_ == other##struct_) {                                  \
+        /* The very same struct, so we know that there will be no */          \
+        /* differences.                                           */          \
+        *aEqualStructs |= NS_STYLE_INHERIT_BIT(struct_);                      \
+      } else if (compare ||                                                   \
+                 ((maxDifference & ~differenceAlwaysHandledForDescendants) &  \
+                  aParentHintsNotHandledForDescendants)) {                    \
+        nsChangeHint difference =                                             \
+          this##struct_->CalcDifference(*other##struct_ EXTRA_DIFF_ARGS);     \
+        NS_ASSERTION(NS_IsHintSubset(difference, maxDifference),              \
+                     "CalcDifference() returned bigger hint than "            \
+                     "MaxDifference()");                                      \
+        hint |= difference;                                                   \
+        if (!difference) {                                                    \
+          *aEqualStructs |= NS_STYLE_INHERIT_BIT(struct_);                    \
+        }                                                                     \
+      } else {                                                                \
+        /* We still must call CalcDifference to see if there were any */      \
+        /* changes so that we can set *aEqualStructs appropriately.   */      \
+        nsChangeHint difference =                                             \
+          this##struct_->CalcDifference(*other##struct_ EXTRA_DIFF_ARGS);     \
+        NS_ASSERTION(NS_IsHintSubset(difference, maxDifference),              \
+                     "CalcDifference() returned bigger hint than "            \
+                     "MaxDifference()");                                      \
+        if (!difference) {                                                    \
+          *aEqualStructs |= NS_STYLE_INHERIT_BIT(struct_);                    \
+        }                                                                     \
+      }                                                                       \
+    } else {                                                                  \
+      *aEqualStructs |= NS_STYLE_INHERIT_BIT(struct_);                        \
+    }                                                                         \
+    styleStructCount++;                                                       \
+  PR_END_MACRO
+
+  // In general, we want to examine structs starting with those that can
+  // cause the largest style change, down to those that can cause the
+  // smallest.  This lets us skip later ones if we already have a hint
+  // that subsumes their MaxDifference.  (As the hints get
+  // finer-grained, this optimization is becoming less useful, though.)
+#define EXTRA_DIFF_ARGS /* nothing */
+  DO_STRUCT_DIFFERENCE(Display);
+  DO_STRUCT_DIFFERENCE(XUL);
+  DO_STRUCT_DIFFERENCE(Column);
+  DO_STRUCT_DIFFERENCE(Content);
+  DO_STRUCT_DIFFERENCE(UserInterface);
+  DO_STRUCT_DIFFERENCE(Visibility);
+  DO_STRUCT_DIFFERENCE(Outline);
+  DO_STRUCT_DIFFERENCE(TableBorder);
+  DO_STRUCT_DIFFERENCE(Table);
+  DO_STRUCT_DIFFERENCE(UIReset);
+  DO_STRUCT_DIFFERENCE(Text);
+  DO_STRUCT_DIFFERENCE(List);
+  DO_STRUCT_DIFFERENCE(SVGReset);
+  DO_STRUCT_DIFFERENCE(SVG);
+#undef EXTRA_DIFF_ARGS
+#define EXTRA_DIFF_ARGS , PeekStyleVisibility()
+  DO_STRUCT_DIFFERENCE(Position);
+#undef EXTRA_DIFF_ARGS
+#define EXTRA_DIFF_ARGS /* nothing */
+  DO_STRUCT_DIFFERENCE(Font);
+  DO_STRUCT_DIFFERENCE(Margin);
+  DO_STRUCT_DIFFERENCE(Padding);
+  DO_STRUCT_DIFFERENCE(Border);
+  DO_STRUCT_DIFFERENCE(TextReset);
+  DO_STRUCT_DIFFERENCE(Effects);
+  DO_STRUCT_DIFFERENCE(Background);
+  DO_STRUCT_DIFFERENCE(Color);
+#undef EXTRA_DIFF_ARGS
+
+#undef DO_STRUCT_DIFFERENCE
+
+  MOZ_ASSERT(styleStructCount == nsStyleStructID_Length,
+             "missing a call to DO_STRUCT_DIFFERENCE");
+
+#ifdef DEBUG
+  #define STYLE_STRUCT(name_, callback_)                                      \
+    MOZ_ASSERT(!!(structsFound & NS_STYLE_INHERIT_BIT(name_)) ==              \
+               !!PeekStyle##name_(),                                          \
+               "PeekStyleData results must not change in the middle of "      \
+               "difference calculation.");
+  #include "nsStyleStructList.h"
+  #undef STYLE_STRUCT
+#endif
+
+  // We check for struct pointer equality here rather than as part of the
+  // DO_STRUCT_DIFFERENCE calls, since those calls can result in structs
+  // we previously examined and found to be null on this style context
+  // getting computed by later DO_STRUCT_DIFFERENCE calls (which can
+  // happen when the nsRuleNode::ComputeXXXData method looks up another
+  // struct.)  This is important for callers in RestyleManager that
+  // need to know the equality or not of the final set of cached struct
+  // pointers.
+  *aSamePointerStructs = 0;
+
+#define STYLE_STRUCT(name_, callback_)                                        \
+  {                                                                           \
+    const nsStyle##name_* data = PeekStyle##name_();                          \
+    if (!data || data == aNewContext->Style##name_()) {                       \
+      *aSamePointerStructs |= NS_STYLE_INHERIT_BIT(name_);                    \
+    }                                                                         \
+  }
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+
+  // Note that we do not check whether this->RelevantLinkVisited() !=
+  // aNewContext->RelevantLinkVisited(); we don't need to since
+  // nsCSSFrameConstructor::DoContentStateChanged always adds
+  // nsChangeHint_RepaintFrame for NS_EVENT_STATE_VISITED changes (and
+  // needs to, since HasStateDependentStyle probably doesn't work right
+  // for NS_EVENT_STATE_VISITED).  Hopefully this doesn't actually
+  // expose whether links are visited to performance tests since all
+  // link coloring happens asynchronously at a time when it's hard for
+  // the page to measure.
+  // However, we do need to compute the larger of the changes that can
+  // happen depending on whether the link is visited or unvisited, since
+  // doing only the one that's currently appropriate would expose which
+  // links are in history to easy performance measurement.  Therefore,
+  // here, we add nsChangeHint_RepaintFrame hints (the maximum for
+  // things that can depend on :visited) for the properties on which we
+  // call GetVisitedDependentColor.
+  nsStyleContext *thisVis = GetStyleIfVisited(),
+                *otherVis = aNewContext->GetStyleIfVisited();
+  if (!thisVis != !otherVis) {
+    // One style context has a style-if-visited and the other doesn't.
+    // Presume a difference.
+    hint |= nsChangeHint_RepaintFrame;
+  } else if (thisVis && !NS_IsHintSubset(nsChangeHint_RepaintFrame, hint)) {
+    // Both style contexts have a style-if-visited.
+    bool change = false;
+
+    // NB: Calling Peek on |this|, not |thisVis|, since callers may look
+    // at a struct on |this| without looking at the same struct on
+    // |thisVis| (including this function if we skip one of these checks
+    // due to change being true already or due to the old style context
+    // not having a style-if-visited), but not the other way around.
+    if (PeekStyleColor()) {
+      if (thisVis->StyleColor()->mColor !=
+          otherVis->StyleColor()->mColor) {
+        change = true;
+      }
+    }
+
+    // NB: Calling Peek on |this|, not |thisVis| (see above).
+    if (!change && PeekStyleBackground()) {
+      if (thisVis->StyleBackground()->mBackgroundColor !=
+          otherVis->StyleBackground()->mBackgroundColor) {
+        change = true;
+      }
+    }
+
+    // NB: Calling Peek on |this|, not |thisVis| (see above).
+    if (!change && PeekStyleBorder()) {
+      const nsStyleBorder *thisVisBorder = thisVis->StyleBorder();
+      const nsStyleBorder *otherVisBorder = otherVis->StyleBorder();
+      NS_FOR_CSS_SIDES(side) {
+        if (thisVisBorder->mBorderColor[side] !=
+            otherVisBorder->mBorderColor[side]) {
+          change = true;
+          break;
+        }
+      }
+    }
+
+    // NB: Calling Peek on |this|, not |thisVis| (see above).
+    if (!change && PeekStyleOutline()) {
+      const nsStyleOutline *thisVisOutline = thisVis->StyleOutline();
+      const nsStyleOutline *otherVisOutline = otherVis->StyleOutline();
+      if (thisVisOutline->mOutlineColor != otherVisOutline->mOutlineColor) {
+        change = true;
+      }
+    }
+
+    // NB: Calling Peek on |this|, not |thisVis| (see above).
+    if (!change && PeekStyleColumn()) {
+      const nsStyleColumn *thisVisColumn = thisVis->StyleColumn();
+      const nsStyleColumn *otherVisColumn = otherVis->StyleColumn();
+      if (thisVisColumn->mColumnRuleColor != otherVisColumn->mColumnRuleColor) {
+        change = true;
+      }
+    }
+
+    // NB: Calling Peek on |this|, not |thisVis| (see above).
+    if (!change && PeekStyleText()) {
+      const nsStyleText* thisVisText = thisVis->StyleText();
+      const nsStyleText* otherVisText = otherVis->StyleText();
+      if (thisVisText->mTextEmphasisColor != otherVisText->mTextEmphasisColor ||
+          thisVisText->mWebkitTextFillColor != otherVisText->mWebkitTextFillColor ||
+          thisVisText->mWebkitTextStrokeColor != otherVisText->mWebkitTextStrokeColor) {
+        change = true;
+      }
+    }
+
+    // NB: Calling Peek on |this|, not |thisVis| (see above).
+    if (!change && PeekStyleTextReset()) {
+      const nsStyleTextReset *thisVisTextReset = thisVis->StyleTextReset();
+      const nsStyleTextReset *otherVisTextReset = otherVis->StyleTextReset();
+      if (thisVisTextReset->mTextDecorationColor !=
+          otherVisTextReset->mTextDecorationColor) {
+        change = true;
+      }
+    }
+
+    // NB: Calling Peek on |this|, not |thisVis| (see above).
+    if (!change && PeekStyleSVG()) {
+      const nsStyleSVG *thisVisSVG = thisVis->StyleSVG();
+      const nsStyleSVG *otherVisSVG = otherVis->StyleSVG();
+      if (thisVisSVG->mFill != otherVisSVG->mFill ||
+          thisVisSVG->mStroke != otherVisSVG->mStroke) {
+        change = true;
+      }
+    }
+
+    if (change) {
+      hint |= nsChangeHint_RepaintFrame;
+    }
+  }
+
+  if (hint & nsChangeHint_UpdateContainingBlock) {
+    // If a struct returned nsChangeHint_UpdateContainingBlock, that
+    // means that one property's influence on whether we're a containing
+    // block for abs-pos or fixed-pos elements has changed.  However, we
+    // only need to return the hint if the overall computation of
+    // whether we establish a containing block has changed.
+
+    // This depends on data in nsStyleDisplay and nsStyleEffects, so we
+    // do it here.
+
+    // Note that it's perhaps good for this test to be last because it
+    // doesn't use Peek* functions to get the structs on the old
+    // context.  But this isn't a big concern because these struct
+    // getters should be called during frame construction anyway.
+    if (StyleDisplay()->IsAbsPosContainingBlockForAppropriateFrame(this) ==
+        aNewContext->StyleDisplay()->
+          IsAbsPosContainingBlockForAppropriateFrame(aNewContext) &&
+        StyleDisplay()->IsFixedPosContainingBlockForAppropriateFrame(this) ==
+        aNewContext->StyleDisplay()->
+          IsFixedPosContainingBlockForAppropriateFrame(aNewContext)) {
+      // While some styles that cause the frame to be a containing block
+      // has changed, the overall result hasn't.
+      hint &= ~nsChangeHint_UpdateContainingBlock;
+    }
+  }
+
+  MOZ_ASSERT(NS_IsHintSubset(hint, nsChangeHint_AllHints),
+             "Added a new hint without bumping AllHints?");
+  return hint & ~nsChangeHint_NeutralChange;
+}
+
+nsChangeHint
+nsStyleContext::CalcStyleDifference(nsStyleContext* aNewContext,
+                                    nsChangeHint aParentHintsNotHandledForDescendants,
+                                    uint32_t* aEqualStructs,
+                                    uint32_t* aSamePointerStructs)
+{
+  return CalcStyleDifferenceInternal(aNewContext, aParentHintsNotHandledForDescendants,
+                                     aEqualStructs, aSamePointerStructs);
+}
+
+class MOZ_STACK_CLASS FakeStyleContext
+{
+public:
+  explicit FakeStyleContext(const ServoComputedValues* aComputedValues)
+    : mComputedValues(aComputedValues) {}
+
+  mozilla::NonOwningStyleContextSource StyleSource() const {
+    return mozilla::NonOwningStyleContextSource(mComputedValues);
+  }
+
+  nsStyleContext* GetStyleIfVisited() {
+    // XXXbholley: This is wrong. Need to implement to get visited handling
+    // corrrect!
+    return nullptr;
+  }
+
+  #define STYLE_STRUCT(name_, checkdata_cb_)                                  \
+  const nsStyle##name_ * Style##name_() {                                     \
+    return Servo_GetStyle##name_(mComputedValues);                            \
+  }
+  #include "nsStyleStructList.h"
+  #undef STYLE_STRUCT
+
+private:
+  const ServoComputedValues* MOZ_NON_OWNING_REF mComputedValues;
+};
+
+nsChangeHint
+nsStyleContext::CalcStyleDifference(const ServoComputedValues* aNewComputedValues,
+                                    nsChangeHint aParentHintsNotHandledForDescendants,
+                                    uint32_t* aEqualStructs,
+                                    uint32_t* aSamePointerStructs)
+{
+  FakeStyleContext newContext(aNewComputedValues);
+  return CalcStyleDifferenceInternal(&newContext, aParentHintsNotHandledForDescendants,
+                                     aEqualStructs, aSamePointerStructs);
+}
+
+#ifdef DEBUG
+void nsStyleContext::List(FILE* out, int32_t aIndent, bool aListDescendants)
+{
+  nsAutoCString str;
+  // Indent
+  int32_t ix;
+  for (ix = aIndent; --ix >= 0; ) {
+    str.AppendLiteral("  ");
+  }
+  str.Append(nsPrintfCString("%p(%d) parent=%p ",
+                             (void*)this, mRefCnt, (void *)mParent));
+  if (mPseudoTag) {
+    nsAutoString  buffer;
+    mPseudoTag->ToString(buffer);
+    AppendUTF16toUTF8(buffer, str);
+    str.Append(' ');
+  }
+
+  if (mSource.IsServoComputedValues()) {
+    fprintf_stderr(out, "%s{ServoComputedValues}\n", str.get());
+  } else if (mSource.IsGeckoRuleNode()) {
+    fprintf_stderr(out, "%s{\n", str.get());
+    str.Truncate();
+    nsRuleNode* ruleNode = mSource.AsGeckoRuleNode();
+    while (ruleNode) {
+      nsIStyleRule *styleRule = ruleNode->GetRule();
+      if (styleRule) {
+        styleRule->List(out, aIndent + 1);
+      }
+      ruleNode = ruleNode->GetParent();
+    }
+    for (ix = aIndent; --ix >= 0; ) {
+      str.AppendLiteral("  ");
+    }
+    fprintf_stderr(out, "%s}\n", str.get());
+  }
+  else {
+    fprintf_stderr(out, "%s{}\n", str.get());
+  }
+
+  if (aListDescendants) {
+    if (nullptr != mChild) {
+      nsStyleContext* child = mChild;
+      do {
+        child->List(out, aIndent + 1, aListDescendants);
+        child = child->mNextSibling;
+      } while (mChild != child);
+    }
+    if (nullptr != mEmptyChild) {
+      nsStyleContext* child = mEmptyChild;
+      do {
+        child->List(out, aIndent + 1, aListDescendants);
+        child = child->mNextSibling;
+      } while (mEmptyChild != child);
+    }
+  }
+}
+#endif
+
+// Overloaded new operator. Initializes the memory to 0 and relies on an arena
+// (which comes from the presShell) to perform the allocation.
+void*
+nsStyleContext::operator new(size_t sz, nsPresContext* aPresContext)
+{
+  // Check the recycle list first.
+  return aPresContext->PresShell()->
+    AllocateByObjectID(eArenaObjectID_nsStyleContext, sz);
+}
+
+// Overridden to prevent the global delete from being called, since the memory
+// came out of an nsIArena instead of the global delete operator's heap.
+void
+nsStyleContext::Destroy()
+{
+  // Get the pres context.
+  RefPtr<nsPresContext> presContext = PresContext();
+
+  // Call our destructor.
+  this->~nsStyleContext();
+
+  // Don't let the memory be freed, since it will be recycled
+  // instead. Don't call the global operator delete.
+  presContext->PresShell()->
+    FreeByObjectID(eArenaObjectID_nsStyleContext, this);
+}
+
+already_AddRefed<nsStyleContext>
+NS_NewStyleContext(nsStyleContext* aParentContext,
+                   nsIAtom* aPseudoTag,
+                   CSSPseudoElementType aPseudoType,
+                   nsRuleNode* aRuleNode,
+                   bool aSkipParentDisplayBasedStyleFixup)
+{
+  RefPtr<nsRuleNode> node = aRuleNode;
+  RefPtr<nsStyleContext> context =
+    new (aRuleNode->PresContext())
+    nsStyleContext(aParentContext, aPseudoTag, aPseudoType, node.forget(),
+                   aSkipParentDisplayBasedStyleFixup);
+  return context.forget();
+}
+
+already_AddRefed<nsStyleContext>
+NS_NewStyleContext(nsStyleContext* aParentContext,
+                   nsPresContext* aPresContext,
+                   nsIAtom* aPseudoTag,
+                   CSSPseudoElementType aPseudoType,
+                   already_AddRefed<ServoComputedValues> aComputedValues,
+                   bool aSkipParentDisplayBasedStyleFixup)
+{
+  RefPtr<nsStyleContext> context =
+    new (aPresContext)
+    nsStyleContext(aParentContext, aPresContext, aPseudoTag, aPseudoType,
+                   Move(aComputedValues), aSkipParentDisplayBasedStyleFixup);
+  return context.forget();
+}
+
+nsIPresShell*
+nsStyleContext::Arena()
+{
+  return PresContext()->PresShell();
+}
+
+static inline void
+ExtractAnimationValue(nsCSSPropertyID aProperty,
+                      nsStyleContext* aStyleContext,
+                      StyleAnimationValue& aResult)
+{
+  DebugOnly<bool> success =
+    StyleAnimationValue::ExtractComputedValue(aProperty, aStyleContext,
+                                              aResult);
+  MOZ_ASSERT(success,
+             "aProperty must be extractable by StyleAnimationValue");
+}
+
+static Maybe<nscolor>
+ExtractColor(nsCSSPropertyID aProperty,
+             nsStyleContext *aStyleContext)
+{
+  StyleAnimationValue val;
+  ExtractAnimationValue(aProperty, aStyleContext, val);
+  switch (val.GetUnit()) {
+    case StyleAnimationValue::eUnit_Color:
+      return Some(val.GetCSSValueValue()->GetColorValue());
+    case StyleAnimationValue::eUnit_CurrentColor:
+      return Some(aStyleContext->StyleColor()->mColor);
+    case StyleAnimationValue::eUnit_ComplexColor:
+      return Some(aStyleContext->StyleColor()->
+                  CalcComplexColor(val.GetStyleComplexColorValue()));
+    default:
+      return Nothing();
+  }
+}
+
+static nscolor
+ExtractColorLenient(nsCSSPropertyID aProperty,
+                    nsStyleContext *aStyleContext)
+{
+  return ExtractColor(aProperty, aStyleContext).valueOr(NS_RGBA(0, 0, 0, 0));
+}
+
+struct ColorIndexSet {
+  uint8_t colorIndex, alphaIndex;
+};
+
+static const ColorIndexSet gVisitedIndices[2] = { { 0, 0 }, { 1, 0 } };
+
+nscolor
+nsStyleContext::GetVisitedDependentColor(nsCSSPropertyID aProperty)
+{
+  NS_ASSERTION(aProperty == eCSSProperty_color ||
+               aProperty == eCSSProperty_background_color ||
+               aProperty == eCSSProperty_border_top_color ||
+               aProperty == eCSSProperty_border_right_color ||
+               aProperty == eCSSProperty_border_bottom_color ||
+               aProperty == eCSSProperty_border_left_color ||
+               aProperty == eCSSProperty_outline_color ||
+               aProperty == eCSSProperty_column_rule_color ||
+               aProperty == eCSSProperty_text_decoration_color ||
+               aProperty == eCSSProperty_text_emphasis_color ||
+               aProperty == eCSSProperty__webkit_text_fill_color ||
+               aProperty == eCSSProperty__webkit_text_stroke_color ||
+               aProperty == eCSSProperty_fill ||
+               aProperty == eCSSProperty_stroke,
+               "we need to add to nsStyleContext::CalcStyleDifference");
+
+  bool isPaintProperty = aProperty == eCSSProperty_fill ||
+                         aProperty == eCSSProperty_stroke;
+
+  nscolor colors[2];
+  colors[0] = isPaintProperty ? ExtractColorLenient(aProperty, this)
+                              : ExtractColor(aProperty, this).value();
+
+  nsStyleContext *visitedStyle = this->GetStyleIfVisited();
+  if (!visitedStyle) {
+    return colors[0];
+  }
+
+  colors[1] = isPaintProperty ? ExtractColorLenient(aProperty, visitedStyle)
+                              : ExtractColor(aProperty, visitedStyle).value();
+
+  return nsStyleContext::CombineVisitedColors(colors,
+                                              this->RelevantLinkVisited());
+}
+
+/* static */ nscolor
+nsStyleContext::CombineVisitedColors(nscolor *aColors, bool aLinkIsVisited)
+{
+  if (NS_GET_A(aColors[1]) == 0) {
+    // If the style-if-visited is transparent, then just use the
+    // unvisited style rather than using the (meaningless) color
+    // components of the visited style along with a potentially
+    // non-transparent alpha value.
+    aLinkIsVisited = false;
+  }
+
+  // NOTE: We want this code to have as little timing dependence as
+  // possible on whether this->RelevantLinkVisited() is true.
+  const ColorIndexSet &set =
+    gVisitedIndices[aLinkIsVisited ? 1 : 0];
+
+  nscolor colorColor = aColors[set.colorIndex];
+  nscolor alphaColor = aColors[set.alphaIndex];
+  return NS_RGBA(NS_GET_R(colorColor), NS_GET_G(colorColor),
+                 NS_GET_B(colorColor), NS_GET_A(alphaColor));
+}
+
+#ifdef DEBUG
+/* static */ void
+nsStyleContext::AssertStyleStructMaxDifferenceValid()
+{
+#define STYLE_STRUCT(name, checkdata_cb)                                     \
+    MOZ_ASSERT(NS_IsHintSubset(nsStyle##name::DifferenceAlwaysHandledForDescendants(), \
+                               nsStyle##name::MaxDifference()));
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+}
+
+/* static */ const char*
+nsStyleContext::StructName(nsStyleStructID aSID)
+{
+  switch (aSID) {
+#define STYLE_STRUCT(name_, checkdata_cb)                                     \
+    case eStyleStruct_##name_:                                                \
+      return #name_;
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+    default:
+      return "Unknown";
+  }
+}
+
+/* static */ bool
+nsStyleContext::LookupStruct(const nsACString& aName, nsStyleStructID& aResult)
+{
+  if (false)
+    ;
+#define STYLE_STRUCT(name_, checkdata_cb_)                                    \
+  else if (aName.EqualsLiteral(#name_))                                       \
+    aResult = eStyleStruct_##name_;
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+  else
+    return false;
+  return true;
+}
+#endif
+
+void
+nsStyleContext::SwapStyleData(nsStyleContext* aNewContext, uint32_t aStructs)
+{
+  static_assert(nsStyleStructID_Length <= 32, "aStructs is not big enough");
+
+  for (nsStyleStructID i = nsStyleStructID_Inherited_Start;
+       i < nsStyleStructID_Inherited_Start + nsStyleStructID_Inherited_Count;
+       i = nsStyleStructID(i + 1)) {
+    uint32_t bit = nsCachedStyleData::GetBitForSID(i);
+    if (!(aStructs & bit)) {
+      continue;
+    }
+    void*& thisData = mCachedInheritedData.mStyleStructs[i];
+    void*& otherData = aNewContext->mCachedInheritedData.mStyleStructs[i];
+    if (mBits & bit) {
+      if (thisData == otherData) {
+        thisData = nullptr;
+      }
+    } else if (!(aNewContext->mBits & bit) && thisData && otherData) {
+      std::swap(thisData, otherData);
+    }
+  }
+
+  for (nsStyleStructID i = nsStyleStructID_Reset_Start;
+       i < nsStyleStructID_Reset_Start + nsStyleStructID_Reset_Count;
+       i = nsStyleStructID(i + 1)) {
+    uint32_t bit = nsCachedStyleData::GetBitForSID(i);
+    if (!(aStructs & bit)) {
+      continue;
+    }
+    if (!mCachedResetData) {
+      mCachedResetData = new (PresContext()) nsResetStyleData;
+    }
+    if (!aNewContext->mCachedResetData) {
+      aNewContext->mCachedResetData = new (PresContext()) nsResetStyleData;
+    }
+    void*& thisData = mCachedResetData->mStyleStructs[i];
+    void*& otherData = aNewContext->mCachedResetData->mStyleStructs[i];
+    if (mBits & bit) {
+      if (thisData == otherData) {
+        thisData = nullptr;
+      }
+    } else if (!(aNewContext->mBits & bit) && thisData && otherData) {
+      std::swap(thisData, otherData);
+    }
+  }
+}
+
+void
+nsStyleContext::ClearCachedInheritedStyleDataOnDescendants(uint32_t aStructs)
+{
+  if (mChild) {
+    nsStyleContext* child = mChild;
+    do {
+      child->DoClearCachedInheritedStyleDataOnDescendants(aStructs);
+      child = child->mNextSibling;
+    } while (mChild != child);
+  }
+  if (mEmptyChild) {
+    nsStyleContext* child = mEmptyChild;
+    do {
+      child->DoClearCachedInheritedStyleDataOnDescendants(aStructs);
+      child = child->mNextSibling;
+    } while (mEmptyChild != child);
+  }
+}
+
+void
+nsStyleContext::DoClearCachedInheritedStyleDataOnDescendants(uint32_t aStructs)
+{
+  NS_ASSERTION(mFrameRefCnt == 0, "frame still referencing style context");
+  for (nsStyleStructID i = nsStyleStructID_Inherited_Start;
+       i < nsStyleStructID_Inherited_Start + nsStyleStructID_Inherited_Count;
+       i = nsStyleStructID(i + 1)) {
+    uint32_t bit = nsCachedStyleData::GetBitForSID(i);
+    if (aStructs & bit) {
+      if (!(mBits & bit) && mCachedInheritedData.mStyleStructs[i]) {
+        aStructs &= ~bit;
+      } else {
+        mCachedInheritedData.mStyleStructs[i] = nullptr;
+      }
+    }
+  }
+
+  if (mCachedResetData) {
+    for (nsStyleStructID i = nsStyleStructID_Reset_Start;
+         i < nsStyleStructID_Reset_Start + nsStyleStructID_Reset_Count;
+         i = nsStyleStructID(i + 1)) {
+      uint32_t bit = nsCachedStyleData::GetBitForSID(i);
+      if (aStructs & bit) {
+        if (!(mBits & bit) && mCachedResetData->mStyleStructs[i]) {
+          aStructs &= ~bit;
+        } else {
+          mCachedResetData->mStyleStructs[i] = nullptr;
+        }
+      }
+    }
+  }
+
+  if (aStructs == 0) {
+    return;
+  }
+
+  ClearCachedInheritedStyleDataOnDescendants(aStructs);
+}
+
+void
+nsStyleContext::SetIneligibleForSharing()
+{
+  if (mBits & NS_STYLE_INELIGIBLE_FOR_SHARING) {
+    return;
+  }
+  mBits |= NS_STYLE_INELIGIBLE_FOR_SHARING;
+  if (mChild) {
+    nsStyleContext* child = mChild;
+    do {
+      child->SetIneligibleForSharing();
+      child = child->mNextSibling;
+    } while (mChild != child);
+  }
+  if (mEmptyChild) {
+    nsStyleContext* child = mEmptyChild;
+    do {
+      child->SetIneligibleForSharing();
+      child = child->mNextSibling;
+    } while (mEmptyChild != child);
+  }
+}
+
+#ifdef RESTYLE_LOGGING
+nsCString
+nsStyleContext::GetCachedStyleDataAsString(uint32_t aStructs)
+{
+  nsCString structs;
+  for (nsStyleStructID i = nsStyleStructID(0);
+       i < nsStyleStructID_Length;
+       i = nsStyleStructID(i + 1)) {
+    if (aStructs & nsCachedStyleData::GetBitForSID(i)) {
+      const void* data = GetCachedStyleData(i);
+      if (!structs.IsEmpty()) {
+        structs.Append(' ');
+      }
+      structs.AppendPrintf("%s=%p", StructName(i), data);
+      if (HasCachedDependentStyleData(i)) {
+        structs.AppendLiteral("(dependent)");
+      } else {
+        structs.AppendLiteral("(owned)");
+      }
+    }
+  }
+  return structs;
+}
+
+int32_t&
+nsStyleContext::LoggingDepth()
+{
+  static int32_t depth = 0;
+  return depth;
+}
+
+void
+nsStyleContext::LogStyleContextTree(int32_t aLoggingDepth, uint32_t aStructs)
+{
+  LoggingDepth() = aLoggingDepth;
+  LogStyleContextTree(true, aStructs);
+}
+
+void
+nsStyleContext::LogStyleContextTree(bool aFirst, uint32_t aStructs)
+{
+  nsCString structs = GetCachedStyleDataAsString(aStructs);
+  if (!structs.IsEmpty()) {
+    structs.Append(' ');
+  }
+
+  nsCString pseudo;
+  if (mPseudoTag) {
+    nsAutoString pseudoTag;
+    mPseudoTag->ToString(pseudoTag);
+    AppendUTF16toUTF8(pseudoTag, pseudo);
+    pseudo.Append(' ');
+  }
+
+  nsCString flags;
+  if (IsStyleIfVisited()) {
+    flags.AppendLiteral("IS_STYLE_IF_VISITED ");
+  }
+  if (HasChildThatUsesGrandancestorStyle()) {
+    flags.AppendLiteral("CHILD_USES_GRANDANCESTOR_STYLE ");
+  }
+  if (IsShared()) {
+    flags.AppendLiteral("IS_SHARED ");
+  }
+
+  nsCString parent;
+  if (aFirst) {
+    parent.AppendPrintf("parent=%p ", mParent.get());
+  }
+
+  LOG_RESTYLE("%p(%d) %s%s%s%s",
+              this, mRefCnt,
+              structs.get(), pseudo.get(), flags.get(), parent.get());
+
+  LOG_RESTYLE_INDENT();
+
+  if (nullptr != mChild) {
+    nsStyleContext* child = mChild;
+    do {
+      child->LogStyleContextTree(false, aStructs);
+      child = child->mNextSibling;
+    } while (mChild != child);
+  }
+  if (nullptr != mEmptyChild) {
+    nsStyleContext* child = mEmptyChild;
+    do {
+      child->LogStyleContextTree(false, aStructs);
+      child = child->mNextSibling;
+    } while (mEmptyChild != child);
+  }
+}
+#endif
+
+#ifdef DEBUG
+/* static */ void
+nsStyleContext::Initialize()
+{
+  Preferences::AddBoolVarCache(
+      &sExpensiveStyleStructAssertionsEnabled,
+      "layout.css.expensive-style-struct-assertions.enabled");
+}
+#endif