Delegate root layer scroll offset to android_webview.

content/public/browser/android/synchronous_compositor.h

Index: content/public/browser/android/synchronous_compositor.h
diff --git a/content/public/browser/android/synchronous_compositor.h b/content/public/browser/android/synchronous_compositor.h
index dbc9af5807577d56227c33bf7dc6ac03dbbb0e50..4eaa5741dff19db4f6477f80849a69b0ce94a248 100644
--- a/content/public/browser/android/synchronous_compositor.h
+++ b/content/public/browser/android/synchronous_compositor.h
@@ -51,6 +51,11 @@ class SynchronousCompositor {
   // and clip set there-in).
   virtual bool DemandDrawSw(SkCanvas* canvas) = 0;
 
+  // Should be called by the embedder after the embedder had modified the
+  // scroll offset of the root layer (as returned by
+  // SynchronousCompositorClient::GetTotalRootLayerScrollOffset).
+  virtual void DidChangeRootLayerScrollOffset() = 0;
+
  protected:
   virtual ~SynchronousCompositor() {}
 };