Handful of changes to get mus to shutdown correctly

components/mus/gles2/gpu_state.h

Index: components/mus/gles2/gpu_state.h
diff --git a/components/mus/gles2/gpu_state.h b/components/mus/gles2/gpu_state.h
index dca04b680a963b9c3a9e48e0c8b1ae1ed0cabfc0..aec23e4f11d399f28143bd3c8642166e7ffa75c9 100644
--- a/components/mus/gles2/gpu_state.h
+++ b/components/mus/gles2/gpu_state.h
@@ -33,7 +33,7 @@ class GpuState : public base::RefCountedThreadSafe<GpuState> {
   // most method class to the CommandBufferDriver, which runs on the "driver",
   // thread (i.e., the thread on which GpuImpl instances are created).
   scoped_refptr<base::SingleThreadTaskRunner> control_task_runner() {
-    return control_thread_.task_runner();
+    return control_thread_task_runner_;
   }
 
   void StopThreads();
@@ -74,11 +74,17 @@ class GpuState : public base::RefCountedThreadSafe<GpuState> {
 
   void InitializeOnGpuThread(base::WaitableEvent* event);
 
+  void DestroyGpuSpecificStateOnGpuThread();
+
   // |gpu_thread_| is for executing OS GL calls.
   base::Thread gpu_thread_;
   // |control_thread_| is for mojo incoming calls of CommandBufferImpl.
   base::Thread control_thread_;
 
+  // Same as control_thread_->task_runner(). The TaskRunner is cached as it may
+  // be needed during shutdown.
+  scoped_refptr<base::SingleThreadTaskRunner> control_thread_task_runner_;
+
   gpu::GpuPreferences gpu_preferences_;
   scoped_refptr<CommandBufferTaskRunner> command_buffer_task_runner_;
   scoped_ptr<CommandBufferDriverManager> driver_manager_;