Added a flag to AudioCodecSpec to indicate adaptive bitrate support.

webrtc/modules/audio_coding/codecs/audio_format.cc

 /*
  *  Copyright (c) 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.
  */
 
@@ skipping 59 matching lines @@
   os << ", parameters: {";
   const char* sep = "";
   for (const auto& kv : saf.parameters) {
     os << sep << kv.first << ": " << kv.second;
     sep = ", ";
   }
   os << "}}";
   return os;
 }
 
+AudioCodecSpec::AudioCodecSpec(const SdpAudioFormat& format)
+    : format(format) {}
+
+AudioCodecSpec::AudioCodecSpec(SdpAudioFormat&& format)
+    : format(std::move(format)) {}
+
 }  // namespace webrtc