Avoid sending empty OnRepaint msgs and propagate window damage correctly

content/browser/renderer_host/render_widget_host_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 
 #include <math.h>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 742 matching lines @@
   if (!view_)
     return NULL;
   return view_->AllocBackingStore(size);
 }
 
 void RenderWidgetHostImpl::DonePaintingToBackingStore() {
   Send(new ViewMsg_UpdateRect_ACK(GetRoutingID()));
 }
 
 void RenderWidgetHostImpl::ScheduleComposite() {
-  if (is_hidden_ || !is_accelerated_compositing_active_) {
+  if (is_hidden_ || !is_accelerated_compositing_active_ ||
+      current_size_.IsEmpty()) {
       return;
   }
 
   // Send out a request to the renderer to paint the view if required.
   if (!repaint_ack_pending_ && !resize_ack_pending_ && !view_being_painted_) {
     repaint_start_time_ = TimeTicks::Now();
     repaint_ack_pending_ = true;
     Send(new ViewMsg_Repaint(routing_id_, current_size_));
   }
 }
@@ skipping 1691 matching lines @@
     return;
 
   OnRenderAutoResized(new_size);
 }
 
 void RenderWidgetHostImpl::DetachDelegate() {
   delegate_ = NULL;
 }
 
 }  // namespace content