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

content/renderer/gpu/compositor_output_surface.cc

Index: content/renderer/gpu/compositor_output_surface.cc
diff --git a/content/renderer/gpu/compositor_output_surface.cc b/content/renderer/gpu/compositor_output_surface.cc
index 93e0fd50f9b14a58b27c48fec74e922e67cb5083..1f1257ebd612ddc75dc02560bf43563d461d3f62 100644
--- a/content/renderer/gpu/compositor_output_surface.cc
+++ b/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()