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..ad27adaa33fab8186745b5b81be19e537ca02bdf 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, or 0 if there is none.
+  virtual int32_t GetCommandBufferRouteId() = 0;
+
   // Caller owns returned pointer, but should call Destroy() on it (instead of
   // directly deleting) for proper destruction, as per the
   // VideoDecodeAccelerator interface.