Bug 996796 patch 18 - Fix RestyleTracker to handle restyle hints exactly rather than pessimistically when restyling continuations with varying styles (e.g., spans inside ::first-line or ::first-letter). r=heycam

This will be necessary when we use the restyle tracker for the
animation-only style flush, because animation-only style flushes need to
update *only* the animation style data and no other style data.  Thus
using the RestyleTracker for animation-only style flushes requires that
we do this.

layout/base/RestyleManager.cpp

@@ -1943,7 +1943,8 @@ GetPrevContinuationWithSameStyle(nsIFrame* aFrame)
  */
 static nsIFrame*
 GetNextContinuationWithSameStyle(nsIFrame* aFrame,
-                                 nsStyleContext* aOldStyleContext)
+                                 nsStyleContext* aOldStyleContext,
+                                 bool* aHaveMoreContinuations = nullptr)
 {
   // See GetPrevContinuationWithSameStyle about {ib} splits.
 
@@ -1973,6 +1974,9 @@ GetNextContinuationWithSameStyle(nsIFrame* aFrame,
                  aOldStyleContext->GetParent() != nextStyle->GetParent(),
                  "continuations should have the same style context");
     nextContinuation = nullptr;
+    if (aHaveMoreContinuations) {
+      *aHaveMoreContinuations = true;
+    }
   }
   return nextContinuation;
 }
@@ -2335,6 +2339,7 @@ ElementRestyler::Restyle(nsRestyleHint aRestyleHint)
   MOZ_ASSERT(!(aRestyleHint & eRestyle_LaterSiblings),
              "eRestyle_LaterSiblings must not be part of aRestyleHint");
 
+  nsRestyleHint hintToRestore = nsRestyleHint(0);
   if (mContent && mContent->IsElement()) {
     mContent->OwnerDoc()->FlushPendingLinkUpdates();
     RestyleTracker::RestyleData restyleData;
@@ -2342,6 +2347,7 @@ ElementRestyler::Restyle(nsRestyleHint aRestyleHint)
       if (NS_UpdateHint(mHintsHandled, restyleData.mChangeHint)) {
         mChangeList->AppendChange(mFrame, mContent, restyleData.mChangeHint);
       }
+      hintToRestore = restyleData.mRestyleHint;
       aRestyleHint = nsRestyleHint(aRestyleHint | restyleData.mRestyleHint);
     }
   }
@@ -2354,10 +2360,20 @@ ElementRestyler::Restyle(nsRestyleHint aRestyleHint)
     // TEMPORARY (until bug 918064):  Call RestyleSelf for each
     // continuation or block-in-inline sibling.
 
+    bool haveMoreContinuations = false;
     for (nsIFrame* f = mFrame; f;
-         f = GetNextContinuationWithSameStyle(f, oldContext)) {
+         f = GetNextContinuationWithSameStyle(f, oldContext,
+                                              &haveMoreContinuations)) {
       RestyleSelf(f, aRestyleHint);
     }
+
+    if (haveMoreContinuations && hintToRestore) {
+      // If we have more continuations with different style (e.g., because
+      // we're inside a ::first-letter or ::first-line), put the restyle
+      // hint back.
+      mRestyleTracker.AddPendingRestyleToTable(mContent->AsElement(),
+                                               hintToRestore, nsChangeHint(0));
+    }
   }
 
   RestyleChildren(childRestyleHint);
@@ -2455,17 +2471,7 @@ ElementRestyler::RestyleSelf(nsIFrame* aSelf, nsRestyleHint aRestyleHint)
                  "non pseudo-element frame without content node");
     newContext = styleSet->ResolveStyleForNonElement(parentContext);
   }
-  else if (!(aRestyleHint & (eRestyle_Self | eRestyle_Subtree)) &&
-           !prevContinuation) {
-    // Unfortunately, if prevContinuation is non-null then we may have
-    // already stolen the restyle tracker entry for this element while
-    // processing prevContinuation.  So we don't know whether aRestyleHint
-    // should really be 0 here or whether it should be eRestyle_Self.  Be
-    // pessimistic and force an actual reresolve in that situation.  The good
-    // news is that in the common case when prevContinuation is non-null we
-    // just used prevContinuationContext anyway and aren't reaching this code
-    // to start with.
-
+  else if (!(aRestyleHint & (eRestyle_Self | eRestyle_Subtree))) {
     Element* element = ElementForStyleContext(mParentContent, aSelf, pseudoType);
     if (aRestyleHint == nsRestyleHint(0)) {
       newContext =

layout/base/RestyleTracker.h

@@ -19,6 +19,7 @@
 namespace mozilla {
 
 class RestyleManager;
+class ElementRestyler;
 
 /** 
  * Helper class that collects a list of frames that need
@@ -230,6 +231,8 @@ class RestyleTracker {
 public:
   typedef mozilla::dom::Element Element;
 
+  friend class ElementRestyler; // for AddPendingRestyleToTable
+
   RestyleTracker(Element::FlagsType aRestyleBits) :
     mRestyleBits(aRestyleBits),
     mHaveLaterSiblingRestyles(false)
@@ -261,7 +264,7 @@ public:
    * if the element already had eRestyle_LaterSiblings set on it.
    */
   bool AddPendingRestyle(Element* aElement, nsRestyleHint aRestyleHint,
-                           nsChangeHint aMinChangeHint);
+                         nsChangeHint aMinChangeHint);
 
   /**
    * Process the restyles we've been tracking.
@@ -312,6 +315,9 @@ public:
   };
 
 private:
+  bool AddPendingRestyleToTable(Element* aElement, nsRestyleHint aRestyleHint,
+                                nsChangeHint aMinChangeHint);
+
   /**
    * Handle a single mPendingRestyles entry.  aRestyleHint must not
    * include eRestyle_LaterSiblings; that needs to be dealt with
@@ -352,9 +358,10 @@ private:
   bool mHaveLaterSiblingRestyles;
 };
 
-inline bool RestyleTracker::AddPendingRestyle(Element* aElement,
-                                                nsRestyleHint aRestyleHint,
-                                                nsChangeHint aMinChangeHint)
+inline bool
+RestyleTracker::AddPendingRestyleToTable(Element* aElement,
+                                         nsRestyleHint aRestyleHint,
+                                         nsChangeHint aMinChangeHint)
 {
   RestyleData existingData;
   existingData.mRestyleHint = nsRestyleHint(0);
@@ -377,6 +384,17 @@ inline bool RestyleTracker::AddPendingRestyle(Element* aElement,
 
   mPendingRestyles.Put(aElement, existingData);
 
+  return hadRestyleLaterSiblings;
+}
+
+inline bool
+RestyleTracker::AddPendingRestyle(Element* aElement,
+                                  nsRestyleHint aRestyleHint,
+                                  nsChangeHint aMinChangeHint)
+{
+  bool hadRestyleLaterSiblings =
+    AddPendingRestyleToTable(aElement, aRestyleHint, aMinChangeHint);
+
   // We can only treat this element as a restyle root if we would
   // actually restyle its descendants (so either call
   // ReResolveStyleContext on it or just reframe it).