Add MediaGpuChannelManager::LookupChannel().

media/renderers/gpu_video_accelerator_factories.h

Index: media/renderers/gpu_video_accelerator_factories.h
diff --git a/media/renderers/gpu_video_accelerator_factories.h b/media/renderers/gpu_video_accelerator_factories.h
index 59695ac76c55dffde7c37d9cd5c83914da8664b0..a8d3c52d6e30a82847e987731254d0191d2c7c8e 100644
--- a/media/renderers/gpu_video_accelerator_factories.h
+++ b/media/renderers/gpu_video_accelerator_factories.h
@@ -73,6 +73,9 @@ class MEDIA_EXPORT GpuVideoAcceleratorFactories {
   // Return the channel token, or an empty token if the channel is unusable.
   virtual base::UnguessableToken GetChannelToken() = 0;
 
+  // Returns the |route_id| of the command buffer.
+  virtual int32_t GetCommandBufferRouteId() = 0;

[tguilbert, 2017/01/10 01:16:35]

Should '0' as the error value be documented?

+
   // Caller owns returned pointer, but should call Destroy() on it (instead of
   // directly deleting) for proper destruction, as per the
   // VideoDecodeAccelerator interface.