Bug 1366721: Restyle additional style contexts in ServoRestyleManager. r=heycam

I was about to assert that other non-primary frames don't have additional style
contexts everywhere, but that wouldn't make much sense, given they don't
correspond to an element we could selector-match against.

MozReview-Commit-ID: EtAQbSg6nP6

--HG--
extra : rebase_source : e9e10c53b7a69506750bd3c7c985946f7027dc30

layout/base/ServoRestyleManager.cpp

@@ -422,6 +422,58 @@ UpdateFirstLetterIfNeeded(nsIFrame* aFrame, ServoRestyleState& aRestyleState)
     UpdateFirstLetterStyle(aRestyleState);
 }
 
+static void
+UpdateOneAdditionalStyleContext(nsIFrame* aFrame,
+                                uint32_t aIndex,
+                                ServoStyleContext& aOldContext,
+                                ServoRestyleState& aRestyleState)
+{
+  auto pseudoType = aOldContext.GetPseudoType();
+  MOZ_ASSERT(pseudoType != CSSPseudoElementType::NotPseudo);
+  MOZ_ASSERT(
+      !nsCSSPseudoElements::PseudoElementSupportsUserActionState(pseudoType));
+
+  RefPtr<ServoStyleContext> newContext =
+    aRestyleState.StyleSet().ResolvePseudoElementStyle(
+        aFrame->GetContent()->AsElement(),
+        pseudoType,
+        aFrame->StyleContext()->AsServo(),
+        /* aPseudoElement = */ nullptr);
+
+  uint32_t equalStructs, samePointerStructs; // Not used, actually.
+  nsChangeHint childHint = aOldContext.CalcStyleDifference(
+    newContext,
+    &equalStructs,
+    &samePointerStructs);
+  if (!aFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW)) {
+    childHint = NS_RemoveSubsumedHints(
+        childHint, aRestyleState.ChangesHandledFor(*aFrame));
+  }
+
+  if (childHint) {
+    aRestyleState.ChangeList().AppendChange(
+        aFrame, aFrame->GetContent(), childHint);
+  }
+
+  aFrame->SetAdditionalStyleContext(aIndex, newContext);
+}
+
+static void
+UpdateAdditionalStyleContexts(nsIFrame* aFrame,
+                              ServoRestyleState& aRestyleState)
+{
+  MOZ_ASSERT(aFrame);
+  MOZ_ASSERT(aFrame->GetContent() && aFrame->GetContent()->IsElement());
+
+  // FIXME(emilio): Consider adding a bit or something to avoid the initial
+  // virtual call?
+  uint32_t index = 0;
+  while (auto* oldContext = aFrame->GetAdditionalStyleContext(index)) {
+    UpdateOneAdditionalStyleContext(
+        aFrame, index++, *oldContext->AsServo(), aRestyleState);
+  }
+}
+
 static void
 UpdateFramePseudoElementStyles(nsIFrame* aFrame,
                                ServoRestyleState& aRestyleState)
@@ -571,6 +623,7 @@ ServoRestyleManager::ProcessPostTraversal(
     // This does mean that we may be setting the wrong style context on our
     // initial continuations; ::first-line fixes that up after the fact.
     for (nsIFrame* f = styleFrame; f; f = f->GetNextContinuation()) {
+      MOZ_ASSERT_IF(f != styleFrame, !f->GetAdditionalStyleContext(0));
       f->SetStyleContext(newContext);
     }
 
@@ -580,6 +633,7 @@ ServoRestyleManager::ProcessPostTraversal(
     }
 
     if (styleFrame) {
+      UpdateAdditionalStyleContexts(styleFrame, aRestyleState);
       styleFrame->UpdateStyleOfOwnedAnonBoxes(childrenRestyleState);
     }
 

layout/generic/nsFrame.cpp

@@ -10257,6 +10257,9 @@ nsIFrame::UpdateStyleOfOwnedChildFrame(
   ServoRestyleState& aRestyleState,
   const Maybe<nsStyleContext*>& aContinuationStyleContext)
 {
+  MOZ_ASSERT(!aChildFrame->GetAdditionalStyleContext(0),
+             "We don't handle additional style contexts here");
+
   // Figure out whether we have an actual change.  It's important that we do
   // this, for several reasons:
   //
@@ -10304,6 +10307,7 @@ nsIFrame::UpdateStyleOfOwnedChildFrame(
   for (nsIFrame* kid = aChildFrame->GetNextContinuation();
        kid;
        kid = kid->GetNextContinuation()) {
+    MOZ_ASSERT(!kid->GetAdditionalStyleContext(0));
     kid->SetStyleContext(continuationStyle);
   }