Avoid sending empty OnRepaint msgs and propagate window damage correctly

content/renderer/gpu/render_widget_compositor.h

 // 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.
 
 #ifndef CONTENT_RENDERER_GPU_RENDER_WIDGET_COMPOSITOR_H_
 #define CONTENT_RENDERER_GPU_RENDER_WIDGET_COMPOSITOR_H_
 
 #include "base/time.h"
 #include "cc/debug/rendering_stats.h"
 #include "cc/trees/layer_tree_host_client.h"
 #include "cc/trees/layer_tree_settings.h"
 #include "skia/ext/refptr.h"
 #include "third_party/WebKit/Source/Platform/chromium/public/WebLayerTreeView.h"
+#include "ui/gfx/rect.h"
 
 class SkPicture;
 
 namespace cc {
 class LayerTreeHost;
 }
 
 namespace content {
 class RenderWidget;
 
 class RenderWidgetCompositor : public WebKit::WebLayerTreeView,
                                public cc::LayerTreeHostClient {
  public:
   // Attempt to construct and initialize a compositor instance for the widget
   // with the given settings. Returns NULL if initialization fails.
   static scoped_ptr<RenderWidgetCompositor> Create(RenderWidget* widget);
 
   virtual ~RenderWidgetCompositor();
 
   void SetSuppressScheduleComposite(bool suppress);
   void Animate(base::TimeTicks time);
   void Composite(base::TimeTicks frame_begin_time);
   void GetRenderingStats(cc::RenderingStats* stats);
   skia::RefPtr<SkPicture> CapturePicture();
   void UpdateTopControlsState(bool enable_hiding,
                               bool enable_showing,
                               bool animate);
   void SetOverdrawBottomHeight(float overdraw_bottom_height);
+  void SetNeedsRedrawRect(gfx::Rect damage_rect);
 
   // WebLayerTreeView implementation.
   virtual void setSurfaceReady();
   virtual void setRootLayer(const WebKit::WebLayer& layer);
   virtual void clearRootLayer();
   virtual void setViewportSize(
       const WebKit::WebSize& unused_deprecated,
       const WebKit::WebSize& device_viewport_size);
   virtual WebKit::WebSize layoutViewportSize() const;
   virtual WebKit::WebSize deviceViewportSize() const;
@@ skipping 53 matching lines @@
   bool threaded_;
   bool suppress_schedule_composite_;
   RenderWidget* widget_;
   scoped_ptr<cc::LayerTreeHost> layer_tree_host_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_GPU_RENDER_WIDGET_COMPOSITOR_H_