Implementing document.setRootScroller API for main thread scrolling.

third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h

Index: third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h
diff --git a/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h b/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h
index e2bd270cfc88fce789d9d62343c9b955c4275fb8..c6113ba7872ce59896a6edfaaae2e20576f1a67a 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h
+++ b/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.h
@@ -11,27 +11,31 @@
 
 namespace blink {
 
-class Document;
 class FloatSize;
 class FrameHost;
 class Element;
 class ScrollableArea;
 class ScrollState;
+class TopControls;
+class OverscrollController;
 
 class ViewportScrollCallback : public ScrollStateCallback {
 public:
-    ViewportScrollCallback(Document&);
+    ViewportScrollCallback(TopControls&, OverscrollController&);
     ~ViewportScrollCallback();
 
     void handleEvent(ScrollState*) override;
 
+    void setScroller(ScrollableArea&);
+
     DECLARE_VIRTUAL_TRACE();
 
 private:
     bool shouldScrollTopControls(const FloatSize&, ScrollGranularity) const;
-    ScrollableArea* getRootFrameViewport() const;
 
-    WeakMember<Document> m_document;
+    WeakMember<TopControls> m_topControls;
+    WeakMember<OverscrollController> m_overscrollController;
+    WeakMember<ScrollableArea> m_scroller;
 };
 
 } // namespace blink