Avoid sending empty OnRepaint msgs and propagate window damage correctly

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 2013 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/renderer/gpu/render_widget_compositor.h"
 
 #include <limits>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 316 matching lines @@
   layer_tree_host_->UpdateTopControlsState(enable_hiding,
                                            enable_showing,
                                            animate);
 }
 
 void RenderWidgetCompositor::SetOverdrawBottomHeight(
     float overdraw_bottom_height) {
   layer_tree_host_->SetOverdrawBottomHeight(overdraw_bottom_height);
 }
 
+void RenderWidgetCompositor::SetNeedsRedrawRect(gfx::Rect damage_rect) {
+  layer_tree_host_->SetNeedsRedrawRect(damage_rect);
+}
+
 bool RenderWidgetCompositor::initialize(cc::LayerTreeSettings settings) {
   scoped_ptr<cc::Thread> impl_thread;
   scoped_refptr<base::MessageLoopProxy> compositor_message_loop_proxy =
       RenderThreadImpl::current()->compositor_message_loop_proxy();
   threaded_ = !!compositor_message_loop_proxy;
   if (threaded_) {
     impl_thread = cc::ThreadImpl::CreateForDifferentThread(
         compositor_message_loop_proxy);
   }
   layer_tree_host_ = cc::LayerTreeHost::Create(this,
@@ skipping 204 matching lines @@
   return RenderThreadImpl::current()->OffscreenContextProviderForMainThread();
 }
 
 scoped_refptr<cc::ContextProvider>
 RenderWidgetCompositor::OffscreenContextProviderForCompositorThread() {
   return RenderThreadImpl::current()->
       OffscreenContextProviderForCompositorThread();
 }
 
 }  // namespace content