Bug 1324618 part 5. Add a way to pass a different style context for later continuations to UpdateStyleOfOwnedChildFrame. r=emilio

We're going to want this for first-letter, because the primary frame and its continuations have different styles.

MozReview-Commit-ID: 6ZjtnRWXgd9

--HG--
extra : rebase_source : 52286f984973b9d0e1a1ea51c439e599eae00a38

layout/generic/nsFrame.cpp

@@ -10245,9 +10245,11 @@ nsIFrame::UpdateStyleOfChildAnonBox(nsIFrame* aChildFrame,
 }
 
 nsChangeHint
-nsIFrame::UpdateStyleOfOwnedChildFrame(nsIFrame* aChildFrame,
-                                       nsStyleContext* aNewStyleContext,
-                                       ServoRestyleState& aRestyleState)
+nsIFrame::UpdateStyleOfOwnedChildFrame(
+  nsIFrame* aChildFrame,
+  nsStyleContext* aNewStyleContext,
+  ServoRestyleState& aRestyleState,
+  const Maybe<nsStyleContext*>& aContinuationStyleContext)
 {
   // Figure out whether we have an actual change.  It's important that we do
   // this, for several reasons:
@@ -10276,8 +10278,13 @@ nsIFrame::UpdateStyleOfOwnedChildFrame(nsIFrame* aChildFrame,
       aChildFrame, aChildFrame->GetContent(), childHint);
   }
 
-  for (nsIFrame* kid = aChildFrame; kid; kid = kid->GetNextContinuation()) {
-    kid->SetStyleContext(aNewStyleContext);
+  aChildFrame->SetStyleContext(aNewStyleContext);
+  nsStyleContext* continuationStyle =
+    aContinuationStyleContext ? *aContinuationStyleContext : aNewStyleContext;
+  for (nsIFrame* kid = aChildFrame->GetNextContinuation();
+       kid;
+       kid = kid->GetNextContinuation()) {
+    kid->SetStyleContext(continuationStyle);
   }
 
   return childHint;

layout/generic/nsIFrame.h

@@ -3329,11 +3329,16 @@ public:
   // `aChildFrame`, and takes care of updating it, calling CalcStyleDifference,
   // and adding to the change list as appropriate.
   //
+  // If aContinuationStyleContext is not Nothing, it should be used for
+  // continuations instead of aNewStyleContext.  In either case, changehints are
+  // only computed based on aNewStyleContext.
+  //
   // Returns the generated change hint for the frame.
   nsChangeHint UpdateStyleOfOwnedChildFrame(
     nsIFrame* aChildFrame,
     nsStyleContext* aNewStyleContext,
-    mozilla::ServoRestyleState& aRestyleState);
+    mozilla::ServoRestyleState& aRestyleState,
+    const Maybe<nsStyleContext*>& aContinuationStyleContext = Nothing());
 
   struct OwnedAnonBox
   {