Add IPC allowing GPU process to tell browser process to temporarily drop a front buffer.

content/browser/gpu/gpu_process_host_ui_shim.cc

Index: content/browser/gpu/gpu_process_host_ui_shim.cc
===================================================================
--- content/browser/gpu/gpu_process_host_ui_shim.cc	(revision 119674)
+++ content/browser/gpu/gpu_process_host_ui_shim.cc	(working copy)
@@ -187,6 +187,8 @@
                         OnAcceleratedSurfaceBuffersSwapped)
     IPC_MESSAGE_HANDLER(GpuHostMsg_AcceleratedSurfacePostSubBuffer,
                         OnAcceleratedSurfacePostSubBuffer)
+    IPC_MESSAGE_HANDLER(GpuHostMsg_AcceleratedSurfaceSuspend,
+                        OnAcceleratedSurfaceSuspend)
     IPC_MESSAGE_HANDLER(GpuHostMsg_GraphicsInfoCollected,
                         OnGraphicsInfoCollected)
 
@@ -371,6 +373,17 @@
   view->AcceleratedSurfacePostSubBuffer(params, host_id_);
 }
 
+void GpuProcessHostUIShim::OnAcceleratedSurfaceSuspend(int32 surface_id) {
+  TRACE_EVENT0("renderer",
+      "GpuProcessHostUIShim::OnAcceleratedSurfaceSuspend");
+
+  RenderWidgetHostView* view = GetRenderWidgetHostViewFromSurfaceID(surface_id);
+  if (!view)
+    return;
+
+  view->AcceleratedSurfaceSuspend();
+}
+
 #if defined(UI_COMPOSITOR_IMAGE_TRANSPORT)
 
 void GpuProcessHostUIShim::OnAcceleratedSurfaceRelease(