Move functionality out from AudioFrame and into AudioFrameOperations.

webrtc/modules/audio_conference_mixer/source/audio_conference_mixer_impl.cc

Index: webrtc/modules/audio_conference_mixer/source/audio_conference_mixer_impl.cc
diff --git a/webrtc/modules/audio_conference_mixer/source/audio_conference_mixer_impl.cc b/webrtc/modules/audio_conference_mixer/source/audio_conference_mixer_impl.cc
index dce3d0b5451b85a7558cb4abf9d5976cde2b005f..d6aa97714f2404f58dda787225c280ad502da518 100644
--- a/webrtc/modules/audio_conference_mixer/source/audio_conference_mixer_impl.cc
+++ b/webrtc/modules/audio_conference_mixer/source/audio_conference_mixer_impl.cc
@@ -40,7 +40,7 @@ void MixFrames(AudioFrame* mixed_frame, AudioFrame* frame, bool use_limiter) {
   if (use_limiter) {
     // Divide by two to avoid saturation in the mixing.
     // This is only meaningful if the limiter will be used.
-    *frame >>= 1;
+    AudioFrameOperations::ShiftDown(frame);

[the sun, 2016/10/19 09:23:16]

Note, if this function was called DivideBy2(), ApplyHalfGain() or similar, the
comment could be removed.

[aleloi, 2016/10/20 08:27:05]

Done.

   }
   if (mixed_frame->num_channels_ > frame->num_channels_) {
     // We only support mono-to-stereo.
@@ -49,7 +49,7 @@ void MixFrames(AudioFrame* mixed_frame, AudioFrame* frame, bool use_limiter) {
     AudioFrameOperations::MonoToStereo(frame);
   }
 
-  *mixed_frame += *frame;
+  AudioFrameOperations::AddFrames(*frame, mixed_frame);
 }
 
 // Return the max number of channels from a |list| composed of AudioFrames.
@@ -284,9 +284,10 @@ void AudioConferenceMixerImpl::Process() {
             std::max(MaxNumChannels(&additionalFramesList),
                      MaxNumChannels(&rampOutList)));
 
-        mixedAudio->UpdateFrame(-1, _timeStamp, NULL, 0, _outputFrequency,
-                                AudioFrame::kNormalSpeech,
-                                AudioFrame::kVadPassive, num_mixed_channels);
+        AudioFrameOperations::UpdateFrame(
+            -1, _timeStamp, NULL, 0, _outputFrequency,
+            AudioFrame::kNormalSpeech, AudioFrame::kVadPassive,
+            num_mixed_channels, mixedAudio);
 
         _timeStamp += static_cast<uint32_t>(_sampleSize);
 
@@ -303,7 +304,7 @@ void AudioConferenceMixerImpl::Process() {
         if(mixedAudio->samples_per_channel_ == 0) {
             // Nothing was mixed, set the audio samples to silence.
             mixedAudio->samples_per_channel_ = _sampleSize;
-            mixedAudio->Mute();
+            AudioFrameOperations::Mute(mixedAudio);
         } else {
             // Only call the limiter if we have something to mix.
             LimitMixedAudio(mixedAudio);
@@ -922,7 +923,7 @@ bool AudioConferenceMixerImpl::LimitMixedAudio(AudioFrame* mixedAudio) const {
     //
     // Instead we double the frame (with addition since left-shifting a
     // negative value is undefined).
-    *mixedAudio += *mixedAudio;
+    AudioFrameOperations::AddFrames(*mixedAudio, mixedAudio);
 
     if(error != _limiter->kNoError) {
         WEBRTC_TRACE(kTraceError, kTraceAudioMixerServer, _id,