Add MojoVideoDecoder.

media/renderers/default_renderer_factory.cc

Index: media/renderers/default_renderer_factory.cc
diff --git a/media/renderers/default_renderer_factory.cc b/media/renderers/default_renderer_factory.cc
index 88fd15789c27ab84cfe9c350a09bca74753072ef..f1530d640cf512ac88153724aa625bcb1aa0f16e 100644
--- a/media/renderers/default_renderer_factory.cc
+++ b/media/renderers/default_renderer_factory.cc
@@ -56,6 +56,8 @@ ScopedVector<AudioDecoder> DefaultRendererFactory::CreateAudioDecoders(
 
   audio_decoders.push_back(new OpusAudioDecoder(media_task_runner));
 
+  // Use an external decoder only if we cannot otherwise decode in the
+  // renderer.
   if (decoder_factory_)
     decoder_factory_->CreateAudioDecoders(&audio_decoders);
 
@@ -69,6 +71,11 @@ ScopedVector<VideoDecoder> DefaultRendererFactory::CreateVideoDecoders(
   // Create our video decoders and renderer.
   ScopedVector<VideoDecoder> video_decoders;
 
+  // Prefer an external decoder since one will only exist if it is hardware
+  // accelerated.
+  if (decoder_factory_)
+    decoder_factory_->CreateVideoDecoders(&video_decoders);
+
   // |gpu_factories_| requires that its entry points be called on its
   // |GetTaskRunner()|.  Since |pipeline_| will own decoders created from the
   // factories, require that their message loops are identical.
@@ -87,9 +94,6 @@ ScopedVector<VideoDecoder> DefaultRendererFactory::CreateVideoDecoders(
   video_decoders.push_back(new FFmpegVideoDecoder());
 #endif
 
-  if (decoder_factory_)
-    decoder_factory_->CreateVideoDecoders(&video_decoders);
-
   return video_decoders;
 }