Add support for external video renderers in mojo.

media/mojo/services/renderer_config.cc

Index: media/mojo/services/renderer_config.cc
diff --git a/media/mojo/services/renderer_config.cc b/media/mojo/services/renderer_config.cc
index 3981ed5a5e523f2ef00fa3beb78205910101fe44..311a260dbac377a029f7dddb4ce1714d34ba90a0 100644
--- a/media/mojo/services/renderer_config.cc
+++ b/media/mojo/services/renderer_config.cc
@@ -24,6 +24,12 @@ ScopedVector<AudioDecoder> RendererConfig::GetAudioDecoders(
   return renderer_config_->GetAudioDecoders(media_task_runner, media_log_cb);
 }
 
+ScopedVector<VideoDecoder> RendererConfig::GetVideoDecoders(
+    const scoped_refptr<base::SingleThreadTaskRunner>& media_task_runner,
+    const LogCB& media_log_cb) {
+  return renderer_config_->GetVideoDecoders(media_task_runner, media_log_cb);
+}
+
 scoped_refptr<AudioRendererSink> RendererConfig::GetAudioRendererSink() {
   return renderer_config_->GetAudioRendererSink();
 }