Early-out from the prepaint tree walk

third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h

Index: third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
diff --git a/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h b/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
index d0c7300095fd2df33147198e94fea34e2351b34e..603fad7e109f1b0a285118950b6940738d61432e 100644
--- a/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
+++ b/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
@@ -22,8 +22,11 @@ class PrePaintTreeWalk {
   void walk(FrameView& rootFrame);
 
  private:
-  void walk(FrameView&, const PrePaintTreeWalkContext&);
-  void walk(const LayoutObject&, const PrePaintTreeWalkContext&);
+  // Throttled rendering (see: FrameView::shouldThrottleRendering()) can prevent
+  // updating a subtree. We return true if the subtree was fully walked/updated,
+  // and false if the walk was interrupted by throttling.
+  bool walk(FrameView&, const PrePaintTreeWalkContext&);
+  bool walk(const LayoutObject&, const PrePaintTreeWalkContext&);
 
   PaintPropertyTreeBuilder m_propertyTreeBuilder;
   PaintInvalidator m_paintInvalidator;