Do not dispatch messages when there is no output surface client.

BUG=142919

Review URL: https://chromiumcodereview.appspot.com/10834339

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151769 0039d316-1c4b-4281-b951-d872f2087c98

content/renderer/gpu/compositor_output_surface.cc

@@ -82,6 +82,8 @@ void CompositorOutputSurface::sendFrameToParentCompositor(
 
 void CompositorOutputSurface::OnMessageReceived(const IPC::Message& message) {
   DCHECK(CalledOnValidThread());
+  if (!client_)
+    return;
   IPC_BEGIN_MESSAGE_MAP(CompositorOutputSurface, message)
     IPC_MESSAGE_HANDLER(ViewMsg_UpdateVSyncParameters, OnUpdateVSyncParameters);
   IPC_END_MESSAGE_MAP()