Adds locks for CommandBufferProxyImpl invalidation

media/gpu/ipc/client/gpu_video_decode_accelerator_host.h

Index: media/gpu/ipc/client/gpu_video_decode_accelerator_host.h
diff --git a/media/gpu/ipc/client/gpu_video_decode_accelerator_host.h b/media/gpu/ipc/client/gpu_video_decode_accelerator_host.h
index 2ba09634b483b851cc02029ad6e4a12cc3ccd76c..a2f6ffde7e3f8826a99b128ca62f8e2b9c31a1d9 100644
--- a/media/gpu/ipc/client/gpu_video_decode_accelerator_host.h
+++ b/media/gpu/ipc/client/gpu_video_decode_accelerator_host.h
@@ -11,6 +11,7 @@
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
 #include "base/threading/non_thread_safe.h"
 #include "gpu/ipc/client/command_buffer_proxy_impl.h"
 #include "ipc/ipc_listener.h"
@@ -86,6 +87,10 @@ class GpuVideoDecodeAcceleratorHost
   // The client that will receive callbacks from the decoder.
   Client* client_;
 
+  // Protect |impl_|. |impl_| is used on media thread, but it can be invalidated
+  // on main thread.
+  base::Lock impl_lock_;
+
   // Unowned reference to the gpu::CommandBufferProxyImpl that created us.
   // |this| registers as a DeletionObserver of |impl_|, the so reference is
   // always valid as long as it is not NULL.
@@ -94,6 +99,10 @@ class GpuVideoDecodeAcceleratorHost
   // Requested dimensions of the buffer, from ProvidePictureBuffers().
   gfx::Size picture_buffer_dimensions_;
 
+  // Task runner for tasks that should run on the thread this class is
+  // constructed.
+  scoped_refptr<base::SingleThreadTaskRunner> media_task_runner_;
+
   // WeakPtr factory for posting tasks back to itself.
   base::WeakPtrFactory<GpuVideoDecodeAcceleratorHost> weak_this_factory_;