Run VDA::Decode on GPU IO thread if VDA supports it.

content/common/gpu/media/gpu_video_decode_accelerator.cc

Index: content/common/gpu/media/gpu_video_decode_accelerator.cc
diff --git a/content/common/gpu/media/gpu_video_decode_accelerator.cc b/content/common/gpu/media/gpu_video_decode_accelerator.cc
index 2b0bb848b69fba9b2acf8d68839441932af28917..fb7bdb8b3a5c3fa96d9bf9b24d599510be0b774c 100644
--- a/content/common/gpu/media/gpu_video_decode_accelerator.cc
+++ b/content/common/gpu/media/gpu_video_decode_accelerator.cc
@@ -63,6 +63,7 @@ GpuVideoDecodeAccelerator::GpuVideoDecodeAccelerator(int32 host_route_id,
   DCHECK(stub_);
   stub_->AddDestructionObserver(this);
   stub_->channel()->AddRoute(host_route_id_, this);
+  stub_->channel()->AddMessageFilterRoute(host_route_id_, this);
   make_context_current_ =
       base::Bind(&MakeDecoderContextCurrent, stub_->AsWeakPtr());
 }
@@ -73,6 +74,7 @@ GpuVideoDecodeAccelerator::~GpuVideoDecodeAccelerator() {
     video_decode_accelerator_.release()->Destroy();
 
   stub_->channel()->RemoveRoute(host_route_id_);
+  stub_->channel()->RemoveMessageFilterRoute(host_route_id_);
   stub_->RemoveDestructionObserver(this);
 }