[RootLayerScrolls] Annotate non-fast-scroll regions to correct layer

third_party/WebKit/Source/platform/scroll/ScrollableArea.h

Index: third_party/WebKit/Source/platform/scroll/ScrollableArea.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollableArea.h b/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
index f5f6a86dd3463eda42ea8a71a86622a9c72d28ce..4df2ffb0bfe153c7fc401710cabc6afbd4c38a90 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
@@ -41,6 +41,7 @@
 
 namespace blink {
 
+class ClientRectList;
 class CompositorAnimationHost;
 class CompositorAnimationTimeline;
 class GraphicsLayer;
@@ -306,6 +307,8 @@ class PLATFORM_EXPORT ScrollableArea : public GarbageCollectedMixin {
   void cancelScrollAnimation();
   virtual void cancelProgrammaticScrollAnimation();
 
+  virtual ClientRectList* nonFastScrollableRects() const { return 0; }
+
   virtual ~ScrollableArea();
 
   // Called when any of horizontal scrollbar, vertical scrollbar and scroll