Support Opus Ambisonics playback

media/renderers/audio_renderer_impl.h

Index: media/renderers/audio_renderer_impl.h
diff --git a/media/renderers/audio_renderer_impl.h b/media/renderers/audio_renderer_impl.h
index f7915d31a607bdc512ac96704a1ddc7085c8d5cf..1f8550df33da64f6fe6ff4a53892e4bccb76c186 100644
--- a/media/renderers/audio_renderer_impl.h
+++ b/media/renderers/audio_renderer_impl.h
@@ -242,6 +242,10 @@ class MEDIA_EXPORT AudioRendererImpl
   // given to the |algorithm_| for efficient playback rate changes.
   ChannelLayout last_decoded_channel_layout_;
 
+  // Similar to |last_decoded_channel_layout_|, used to configure the channel
+  // mask given to the |algorithm_| for efficient playback rate changes.
+  int last_decoded_channels_;
+
   // After Initialize() has completed, all variables below must be accessed
   // under |lock_|. ------------------------------------------------------------
   base::Lock lock_;