Add a NeededFrequency() method to the AudioMixer::Source interface.

webrtc/voice_engine/channel_proxy.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 203 matching lines @@
   channel()->SetRtcEventLog(event_log);
 }
 
 AudioMixer::Source::AudioFrameInfo ChannelProxy::GetAudioFrameWithInfo(
     int sample_rate_hz,
     AudioFrame* audio_frame) {
   RTC_DCHECK_RUNS_SERIALIZED(&race_checker_);
   return channel()->GetAudioFrameWithInfo(sample_rate_hz, audio_frame);
 }
 
+int ChannelProxy::NeededFrequency() const {
+  return static_cast<int>(channel()->NeededFrequency(-1));
+}
+
 Channel* ChannelProxy::channel() const {
   RTC_DCHECK(channel_owner_.channel());
   return channel_owner_.channel();
 }
 
 }  // namespace voe
 }  // namespace webrtc