Add MediaGpuChannelManager::LookupChannel().

content/renderer/media/renderer_gpu_video_accelerator_factories.cc

Index: content/renderer/media/renderer_gpu_video_accelerator_factories.cc
diff --git a/content/renderer/media/renderer_gpu_video_accelerator_factories.cc b/content/renderer/media/renderer_gpu_video_accelerator_factories.cc
index 1fbdb829d93a9dbf2c364afb21ed0418bedf90fc..dff894ac58efdab4fd319e578aaeb671c15890df 100644
--- a/content/renderer/media/renderer_gpu_video_accelerator_factories.cc
+++ b/content/renderer/media/renderer_gpu_video_accelerator_factories.cc
@@ -127,6 +127,13 @@ base::UnguessableToken RendererGpuVideoAcceleratorFactories::GetChannelToken() {
   return channel_token_;
 }
 
+int32_t RendererGpuVideoAcceleratorFactories::GetCommandBufferRouteId() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  if (!context_provider_)
+    return 0;
+  return context_provider_->GetCommandBufferProxy()->route_id();
+}
+
 std::unique_ptr<media::VideoDecodeAccelerator>
 RendererGpuVideoAcceleratorFactories::CreateVideoDecodeAccelerator() {
   DCHECK(video_accelerator_enabled_);