Replace AudioConferenceMixer with AudioMixer.

webrtc/modules/audio_mixer/audio_mixer_impl.cc

 /*
  *  Copyright (c) 2012 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 362 matching lines @@
   rtc::CritScope lock(&crit_);
 
   const auto iter = FindSourceInList(audio_source, &audio_source_list_);
   if (iter != audio_source_list_.end()) {
     return (*iter)->is_mixed;
   }
 
   LOG(LS_ERROR) << "Audio source unknown";
   return false;
 }
+
+bool AudioMixerImpl::GetSourcePresenceStatusForTest(
+    AudioMixerImpl::Source* audio_source) const {
+  RTC_DCHECK_RUNS_SERIALIZED(&race_checker_);
+  rtc::CritScope lock(&crit_);
+
+  const auto iter = FindSourceInList(audio_source, &audio_source_list_);
+  return iter != audio_source_list_.end();
+}
 }  // namespace webrtc