Remove the VoiceEngineObserver callback interface.

test/mock_voice_engine.h

 /*
  *  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 76 matching lines @@
   // Allows injecting a ChannelProxy factory.
   MOCK_METHOD1(ChannelProxyFactory, voe::ChannelProxy*(int channel_id));
 
   // VoiceEngineImpl
   virtual std::unique_ptr<voe::ChannelProxy> GetChannelProxy(
       int channel_id) /* override */ {
     return std::unique_ptr<voe::ChannelProxy>(ChannelProxyFactory(channel_id));
   }
 
   // VoEBase
-  MOCK_METHOD1(RegisterVoiceEngineObserver, int(VoiceEngineObserver& observer));
-  MOCK_METHOD0(DeRegisterVoiceEngineObserver, int());
   MOCK_METHOD3(
       Init,
       int(AudioDeviceModule* external_adm,
           AudioProcessing* external_apm,
           const rtc::scoped_refptr<AudioDecoderFactory>& decoder_factory));
   MOCK_METHOD0(audio_device_module, AudioDeviceModule*());
   MOCK_METHOD0(transmit_mixer, voe::TransmitMixer*());
   MOCK_METHOD0(Terminate, int());
   MOCK_METHOD0(CreateChannel, int());
   MOCK_METHOD1(CreateChannel, int(const ChannelConfig& config));
@@ skipping 15 matching lines @@
 
   std::map<int, std::unique_ptr<MockRtpRtcp>> mock_rtp_rtcps_;
 
   MockAudioDeviceModule mock_audio_device_;
   MockAudioTransport mock_audio_transport_;
 };
 }  // namespace test
 }  // namespace webrtc
 
 #endif  // AUDIO_MOCK_VOICE_ENGINE_H_