Make RootScroller set the outer viewport scroll layer in the compositor

third_party/WebKit/Source/core/page/ChromeClient.h

Index: third_party/WebKit/Source/core/page/ChromeClient.h
diff --git a/third_party/WebKit/Source/core/page/ChromeClient.h b/third_party/WebKit/Source/core/page/ChromeClient.h
index 6f55c92a086890b6b9452a03ce54111917ad9e03..1cda8496fa1aa9d57483f505480b613598f3035f 100644
--- a/third_party/WebKit/Source/core/page/ChromeClient.h
+++ b/third_party/WebKit/Source/core/page/ChromeClient.h
@@ -70,6 +70,7 @@ class PopupOpeningObserver;
 class WebDragData;
 class WebFrameScheduler;
 class WebImage;
+class WebLayer;
 
 struct CompositedSelection;
 struct DateTimeChooserParameters;
@@ -266,6 +267,7 @@ public:
     virtual void onMouseDown(Node*) { }
 
     virtual void didUpdateTopControls() const { }
+    virtual void didUpdateRootScrollerLayer(WebLayer*) const { }
 
     virtual void registerPopupOpeningObserver(PopupOpeningObserver*) = 0;
     virtual void unregisterPopupOpeningObserver(PopupOpeningObserver*) = 0;