AudioDecoder: New method SampleRateHz, + implementations for our codecs

webrtc/modules/audio_coding/codecs/opus/audio_decoder_opus.cc

 /*
  *  Copyright (c) 2015 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 69 matching lines @@
   return WebRtcOpus_FecDurationEst(encoded, encoded_len);
 }
 
 bool AudioDecoderOpus::PacketHasFec(const uint8_t* encoded,
                                     size_t encoded_len) const {
   int fec;
   fec = WebRtcOpus_PacketHasFec(encoded, encoded_len);
   return (fec == 1);
 }
 
+int AudioDecoderOpus::SampleRateHz() const {
+  return 48000;
+}
+
 size_t AudioDecoderOpus::Channels() const {
   return channels_;
 }
 
 }  // namespace webrtc