Revert of Stop caching supported codecs in WebRtcVideoEngine2

webrtc/media/base/mediaengine.h

Index: webrtc/media/base/mediaengine.h
diff --git a/webrtc/media/base/mediaengine.h b/webrtc/media/base/mediaengine.h
index edf0cb0f30a324bb72f93c50fd260e236b241ba2..d1d162370d494c17649e21ec72b28f363d7143ac 100644
--- a/webrtc/media/base/mediaengine.h
+++ b/webrtc/media/base/mediaengine.h
@@ -74,7 +74,7 @@
   virtual const std::vector<AudioCodec>& audio_send_codecs() = 0;
   virtual const std::vector<AudioCodec>& audio_recv_codecs() = 0;
   virtual RtpCapabilities GetAudioCapabilities() = 0;
-  virtual const std::vector<VideoCodec> video_codecs() = 0;
+  virtual const std::vector<VideoCodec>& video_codecs() = 0;
   virtual RtpCapabilities GetVideoCapabilities() = 0;
 
   // Starts AEC dump using existing file, a maximum file size in bytes can be
@@ -147,7 +147,7 @@
   virtual RtpCapabilities GetAudioCapabilities() {
     return voice_.GetCapabilities();
   }
-  virtual const std::vector<VideoCodec> video_codecs() {
+  virtual const std::vector<VideoCodec>& video_codecs() {
     return video_.codecs();
   }
   virtual RtpCapabilities GetVideoCapabilities() {