Revert of Remove ignored return code from modules.

webrtc/modules/audio_conference_mixer/source/audio_conference_mixer_impl.h

 /*
  *  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 46 matching lines @@
     enum {kProcessPeriodicityInMs = 10};
 
     AudioConferenceMixerImpl(int id);
     ~AudioConferenceMixerImpl();
 
     // Must be called after ctor.
     bool Init();
 
     // Module functions
     int64_t TimeUntilNextProcess() override;
-    void Process() override;
+    int32_t Process() override;
 
     // AudioConferenceMixer functions
     int32_t RegisterMixedStreamCallback(
         AudioMixerOutputReceiver* mixReceiver) override;
     int32_t UnRegisterMixedStreamCallback() override;
     int32_t SetMixabilityStatus(MixerParticipant* participant,
                                 bool mixable) override;
     bool MixabilityStatus(const MixerParticipant& participant) const override;
     int32_t SetMinimumMixingFrequency(Frequency freq) override;
     int32_t SetAnonymousMixabilityStatus(
@@ skipping 99 matching lines @@
     // Counter keeping track of concurrent calls to process.
     // Note: should never be higher than 1 or lower than 0.
     int16_t _processCalls;
 
     // Used for inhibiting saturation in mixing.
     rtc::scoped_ptr<AudioProcessing> _limiter;
 };
 }  // namespace webrtc
 
 #endif // WEBRTC_MODULES_AUDIO_CONFERENCE_MIXER_SOURCE_AUDIO_CONFERENCE_MIXER_IMPL_H_