Defer scroll offset change notification to browser

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 46b4f74666d5a47078ad74f16adc7ce92c8c8883..af6a09b68f9c71c001b2f2230929a480e200d1ed 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -718,6 +718,7 @@ RenderViewImpl::RenderViewImpl(RenderViewImplParams* params)
       top_controls_constraints_(cc::BOTH),
 #endif
       has_scrolled_focused_editable_node_into_rect_(false),
+      has_scrolled_main_frame_(false),
       speech_recognition_dispatcher_(NULL),
       browser_plugin_manager_(NULL),
       devtools_agent_(NULL),
@@ -2504,15 +2505,19 @@ BrowserPluginManager* RenderViewImpl::GetBrowserPluginManager() {
   return browser_plugin_manager_.get();
 }
 
-void RenderViewImpl::UpdateScrollState(WebFrame* frame) {
-  Send(new ViewHostMsg_DidChangeScrollOffset(routing_id_));
+void RenderViewImpl::didCommitAndDrawCompositorFrame() {
+  RenderWidget::didCommitAndDrawCompositorFrame();
+  if (has_scrolled_main_frame_) {
+    has_scrolled_main_frame_ = false;
+    Send(new ViewHostMsg_DidChangeScrollOffset(routing_id_));
+  }
 }
 
 void RenderViewImpl::didChangeScrollOffset(WebLocalFrame* frame) {
   StartNavStateSyncTimerIfNecessary();
 
   if (webview()->mainFrame() == frame)
-    UpdateScrollState(frame);
+    has_scrolled_main_frame_ = true;
 
   FOR_EACH_OBSERVER(
       RenderViewObserver, observers_, DidChangeScrollOffset(frame));
@@ -3340,7 +3345,7 @@ void RenderViewImpl::OnResize(const ViewMsg_Resize_Params& params) {
           ShouldDisplayScrollbars(params.new_size.width(),
                                   params.new_size.height()));
     }
-    UpdateScrollState(webview()->mainFrame());
+    has_scrolled_main_frame_ = true;
   }
 
   gfx::Size old_visible_viewport_size = visible_viewport_size_;