Updated mixer unittests and fixed a related bug in the new mixer.

webrtc/modules/audio_mixer/new_audio_conference_mixer_impl.cc

Index: webrtc/modules/audio_mixer/new_audio_conference_mixer_impl.cc
diff --git a/webrtc/modules/audio_mixer/new_audio_conference_mixer_impl.cc b/webrtc/modules/audio_mixer/new_audio_conference_mixer_impl.cc
index 0485e37819e9c6dc518e7a81ba9e252f0a5fb326..535cc7e12a31d407af18a66382cab97c805d60af 100644
--- a/webrtc/modules/audio_mixer/new_audio_conference_mixer_impl.cc
+++ b/webrtc/modules/audio_mixer/new_audio_conference_mixer_impl.cc
@@ -187,7 +187,6 @@ void NewAudioConferenceMixerImpl::Mix(int sample_rate,
                                       size_t number_of_channels,
                                       AudioFrame* audio_frame_for_mixing) {
   RTC_DCHECK(number_of_channels == 1 || number_of_channels == 2);
-  size_t remainingAudioSourcesAllowedToMix = kMaximumAmountOfMixedAudioSources;
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
   AudioFrameList mixList;
   AudioFrameList additionalFramesList;
@@ -218,8 +217,7 @@ void NewAudioConferenceMixerImpl::Mix(int sample_rate,
       SetOutputFrequency(mixing_frequency);
     }
 
-    mixList = UpdateToMix(remainingAudioSourcesAllowedToMix);
-    remainingAudioSourcesAllowedToMix -= mixList.size();

[aleloi, 2016/08/18 09:21:14]

The changes above are a simplification of the handling for the number of
participants. With the new mixer, it may happen that mixList.size() >
kMaximumAmountOfMixedAudioSources, because RampOut participants are also placed
in mixList.

+    mixList = UpdateToMix(kMaximumAmountOfMixedAudioSources);
     GetAdditionalAudio(&additionalFramesList);
   }
 
@@ -526,15 +524,6 @@ int32_t NewAudioConferenceMixerImpl::MixFromList(
 
   for (AudioFrameList::const_iterator iter = audioFrameList.begin();
        iter != audioFrameList.end(); ++iter) {
-    if (position >= kMaximumAmountOfMixedAudioSources) {
-      WEBRTC_TRACE(
-          kTraceMemory, kTraceAudioMixerServer, id,
-          "Trying to mix more than max amount of mixed audio sources:%d!",
-          kMaximumAmountOfMixedAudioSources);
-      // Assert and avoid crash
-      RTC_NOTREACHED();
-      position = 0;
-    }

[aleloi, 2016/08/18 09:21:14]

It may happen that audioFrameList.size() > kMax..Sources, because RampOut
participants are placed in mixList.

     if (!iter->muted) {
       MixFrames(mixedAudio, iter->frame, use_limiter);
     }