Bug 1374761 part 1. Properly restyle the viewport and its child anonymous box when we do a restyle. r=heycam

The child anon box may be an nsHTMLScrollFrame, a nsRootBoxFrame, or a
nsSimplePageSequenceFrame.   nsHTMLScrollFrame already knows how to deal with
its anonymous box kids, nsRootBoxFrame doesn't have any, and the next changeset
will deal with anon box kids of nsSimplePageSequenceFrame.

MozReview-Commit-ID: 2ZV061EhRmc

--HG--
extra : rebase_source : 43084315454284fc6d7353ccdb20137611b2ee46

layout/base/ServoRestyleManager.cpp

@@ -10,6 +10,7 @@
 #include "mozilla/ServoBindings.h"
 #include "mozilla/ServoStyleSet.h"
 #include "mozilla/Unused.h"
+#include "mozilla/ViewportFrame.h"
 #include "mozilla/dom/ChildIterator.h"
 #include "mozilla/dom/ElementInlines.h"
 #include "nsBlockFrame.h"
@@ -432,6 +433,15 @@ ServoRestyleManager::ProcessPostTraversal(Element* aElement,
       UpdateFramePseudoElementStyles(styleFrame, *aStyleSet, aChangeList);
     }
 
+    if (!aElement->GetParent()) {
+      // This is the root.  Update styles on the viewport as needed.
+      ViewportFrame* viewport =
+        do_QueryFrame(mPresContext->PresShell()->GetRootFrame());
+      if (viewport) {
+        viewport->UpdateStyle(*aStyleSet, aChangeList);
+      }
+    }
+
     // Some changes to animations don't affect the computed style and yet still
     // require the layer to be updated. For example, pausing an animation via
     // the Web Animations API won't affect an element's style but still

layout/base/nsCSSFrameConstructor.cpp

@@ -2761,6 +2761,8 @@ nsCSSFrameConstructor::ConstructRootFrame()
   // What would that break?
   viewportFrame->Init(nullptr, nullptr, nullptr);
 
+  viewportFrame->AddStateBits(NS_FRAME_OWNS_ANON_BOXES);
+
   // Bind the viewport frame to the root view
   nsView* rootView = mPresShell->GetViewManager()->GetRootView();
   viewportFrame->SetView(rootView);

layout/generic/ViewportFrame.cpp

@@ -415,6 +415,35 @@ ViewportFrame::ComputeCustomOverflow(nsOverflowAreas& aOverflowAreas)
   return nsContainerFrame::ComputeCustomOverflow(aOverflowAreas);
 }
 
+void
+ViewportFrame::UpdateStyle(ServoStyleSet& aStyleSet,
+                           nsStyleChangeList& aChangeList)
+{
+  nsStyleContext* oldContext = StyleContext();
+  nsIAtom* pseudo = oldContext->GetPseudo();
+  RefPtr<nsStyleContext> newContext =
+    aStyleSet.ResolveInheritingAnonymousBoxStyle(pseudo, nullptr);
+
+  // We're special because we have a null GetContent(), so don't call things
+  // like UpdateStyleOfOwnedChildFrame that try to append changes for the
+  // content to the change list.  Nor do we computed a changehint, since we have
+  // no way to apply it anyway.
+  newContext->EnsureSameStructsCached(oldContext);
+
+  MOZ_ASSERT(!GetNextContinuation(), "Viewport has continuations?");
+  SetStyleContext(newContext);
+
+  UpdateStyleOfOwnedAnonBoxes(aStyleSet, aChangeList, nsChangeHint_Empty);
+}
+
+void
+ViewportFrame::AppendDirectlyOwnedAnonBoxes(nsTArray<OwnedAnonBox>& aResult)
+{
+  if (mFrames.NotEmpty()) {
+    aResult.AppendElement(mFrames.FirstChild());
+  }
+}
+
 #ifdef DEBUG_FRAME_DUMP
 nsresult
 ViewportFrame::GetFrameName(nsAString& aResult) const

layout/generic/ViewportFrame.h

@@ -72,6 +72,17 @@ public:
    */
   nsRect AdjustReflowInputAsContainingBlock(ReflowInput* aReflowInput) const;
 
+  /**
+   * Update our style (and recursively the styles of any anonymous boxes we
+   * might own)
+   */
+  void UpdateStyle(ServoStyleSet& aStyleSet, nsStyleChangeList& aChangeList);
+
+  /**
+   * Return our single anonymous box child.
+   */
+  void AppendDirectlyOwnedAnonBoxes(nsTArray<OwnedAnonBox>& aResult) override;
+
 #ifdef DEBUG_FRAME_DUMP
   virtual nsresult GetFrameName(nsAString& aResult) const override;
 #endif

layout/generic/nsFrame.cpp

@@ -10208,7 +10208,8 @@ nsIFrame::UpdateStyleOfChildAnonBox(nsIFrame* aChildFrame,
 {
   MOZ_ASSERT(aChildFrame->GetParent() == this,
              "This should only be used for children!");
-  MOZ_ASSERT(aChildFrame->GetContent() == GetContent(),
+  MOZ_ASSERT((!GetContent() && IsViewportFrame()) ||
+             aChildFrame->GetContent() == GetContent(),
              "What content node is it a frame for?");
   MOZ_ASSERT(!aChildFrame->GetPrevContinuation(),
              "Only first continuations should end up here");