Plumb the partial swap though image transport.

content/browser/renderer_host/render_widget_host_view.h

Index: content/browser/renderer_host/render_widget_host_view.h
diff --git a/content/browser/renderer_host/render_widget_host_view.h b/content/browser/renderer_host/render_widget_host_view.h
index 44a8427b6b6f499e62345813e6d055083117b925..6ed0974d5e80e6cead1455099793e7f164c42879 100644
--- a/content/browser/renderer_host/render_widget_host_view.h
+++ b/content/browser/renderer_host/render_widget_host_view.h
@@ -27,6 +27,7 @@
 #include "ui/gfx/surface/transport_dib.h"
 
 struct GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params;
+struct GpuHostMsg_AcceleratedSurfacePostSubBuffer_Params;
 
 class BackingStore;
 class RenderWidgetHost;
@@ -197,6 +198,11 @@ class RenderWidgetHostView {
   virtual void AcceleratedSurfaceBuffersSwapped(
       const GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params& params,
       int gpu_host_id) = 0;
+  // Similar to above, except |params.(x|y|width|height)| define the region
+  // of the surface that changed.
+  virtual void AcceleratedSurfacePostSubBuffer(
+      const GpuHostMsg_AcceleratedSurfacePostSubBuffer_Params& params,
+      int gpu_host_id) = 0;
 
 #if defined(OS_MACOSX)
   // Tells the view whether or not to accept first responder status.  If |flag|