Add AudioReceiveStream::SetGain() method and use that in WVoMC::SetOutputVolume().

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 175 matching lines @@
   // May be called on either worker thread or network thread.
   return channel()->ReceivedRTPPacket(packet, length, packet_time) == 0;
 }
 
 bool ChannelProxy::ReceivedRTCPPacket(const uint8_t* packet, size_t length) {
   // May be called on either worker thread or network thread.
   return channel()->ReceivedRTCPPacket(packet, length) == 0;
 }
 
 const rtc::scoped_refptr<AudioDecoderFactory>&
-ChannelProxy::GetAudioDecoderFactory() const {
+    ChannelProxy::GetAudioDecoderFactory() const {
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
   return channel()->GetAudioDecoderFactory();
 }
 
+void ChannelProxy::SetChannelOutputVolumeScaling(float scaling) {
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  int error = channel()->SetChannelOutputVolumeScaling(scaling);
+  RTC_DCHECK_EQ(0, error);
+}
+
 Channel* ChannelProxy::channel() const {
   RTC_DCHECK(channel_owner_.channel());
   return channel_owner_.channel();
 }
 
 }  // namespace voe
 }  // namespace webrtc