Fix errors in destruction sequence of GpuVideoEncodeAccelerator::OnWillDestroyStub()

media/gpu/ipc/service/gpu_video_encode_accelerator.h

Index: media/gpu/ipc/service/gpu_video_encode_accelerator.h
diff --git a/media/gpu/ipc/service/gpu_video_encode_accelerator.h b/media/gpu/ipc/service/gpu_video_encode_accelerator.h
index 351a97c3eef4df19dd890db24d52129a0c793c6d..f6ed332ddc955ef2872edf679b9129f97fe2cb8c 100644
--- a/media/gpu/ipc/service/gpu_video_encode_accelerator.h
+++ b/media/gpu/ipc/service/gpu_video_encode_accelerator.h
@@ -159,12 +159,16 @@ class GpuVideoEncodeAccelerator
   // otherwise |main_thread_task_runner_|.
   scoped_refptr<base::SingleThreadTaskRunner> encode_task_runner_;
 
+  base::WeakPtr<GpuVideoEncodeAccelerator> weak_this_for_encoder_worker_;
+  base::WeakPtr<GpuVideoEncodeAccelerator> weak_this_;
+
   // Weak pointer for referring back to |this| on |encoder_worker_task_runner_|.
   base::WeakPtrFactory<GpuVideoEncodeAccelerator>
       weak_this_factory_for_encoder_worker_;
 
   // Weak pointer for VideoFrames that refer back to |this| on
-  // |main_task_runner| or |io_task_runner_|.
+  // |main_task_runner| or |io_task_runner_|. |io_task_runner_| is used if and
+  // only if |filter_| is applied.
   base::WeakPtrFactory<GpuVideoEncodeAccelerator> weak_this_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuVideoEncodeAccelerator);