Plumb the partial swap though image transport.

content/browser/renderer_host/render_widget_host.cc

 // Copyright (c) 2011 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.h"
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 1461 matching lines @@
       Send(new ViewMsg_LockMouse_ACK(routing_id_, false));
       return false;
     } else {
       Send(new ViewMsg_LockMouse_ACK(routing_id_, true));
       return true;
     }
   }
 }
 
 #if defined(OS_MACOSX) || defined(UI_COMPOSITOR_IMAGE_TRANSPORT)
+// static
 void RenderWidgetHost::AcknowledgeSwapBuffers(int32 route_id, int gpu_host_id) {
   GpuProcessHostUIShim* ui_shim = GpuProcessHostUIShim::FromID(gpu_host_id);
   if (ui_shim)
     ui_shim->Send(new AcceleratedSurfaceMsg_BuffersSwappedACK(route_id));
 }
+
+// static
+void RenderWidgetHost::AcknowledgePostSubBuffer(int32 route_id,
+                                                int gpu_host_id) {
+  GpuProcessHostUIShim* ui_shim = GpuProcessHostUIShim::FromID(gpu_host_id);
+  if (ui_shim)
+    ui_shim->Send(new AcceleratedSurfaceMsg_PostSubBufferACK(route_id));
+}
 #endif