Adding "adapter" ORTC objects on top of ChannelManager/BaseChannel/etc.

webrtc/api/mediatypes.h

 /*
  *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_API_MEDIATYPES_H_
 #define WEBRTC_API_MEDIATYPES_H_
 
 #include <string>
 
 namespace cricket {
 
 enum MediaType {
   MEDIA_TYPE_AUDIO,
   MEDIA_TYPE_VIDEO,
   MEDIA_TYPE_DATA
 };
 
 std::string MediaTypeToString(MediaType type);
+// Aborts on invalid string. Only expected to be used on strings that are
+// guaranteed to be valid, such as MediaStreamTrackInterface::kind().
+MediaType MediaTypeFromString(const std::string& type_str);
 
 }  // namespace cricket
 
 #endif  // WEBRTC_API_MEDIATYPES_H_