Fix iOS GN build and cleanup system_wrappers

webrtc/modules/audio_device/ios/audio_device_ios.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 74 matching lines @@
   // Native audio parameters stored during construction.
   // These methods are unique for the iOS implementation.
   int GetPlayoutAudioParameters(AudioParameters* params) const override;
   int GetRecordAudioParameters(AudioParameters* params) const override;
 
   // These methods are currently not fully implemented on iOS:
 
   // See audio_device_not_implemented.cc for trivial implementations.
   int32_t PlayoutBuffer(AudioDeviceModule::BufferType& type,
                         uint16_t& sizeMS) const override;
-  int32_t ActiveAudioLayer(AudioDeviceModule::AudioLayer& audioLayer) const;
+  int32_t ActiveAudioLayer(
+      AudioDeviceModule::AudioLayer& audioLayer) const override;
   int32_t ResetAudioDevice() override;
   int32_t PlayoutIsAvailable(bool& available) override;
   int32_t RecordingIsAvailable(bool& available) override;
   int32_t SetAGC(bool enable) override;
   bool AGC() const override;
   int16_t PlayoutDevices() override;
   int16_t RecordingDevices() override;
   int32_t PlayoutDeviceName(uint16_t index,
                             char name[kAdmMaxDeviceNameSize],
                             char guid[kAdmMaxGuidSize]) override;
@@ skipping 185 matching lines @@
   // Audio interruption observer instance.
   RTCAudioSessionDelegateAdapter* audio_session_observer_;
 
   // Set to true if we've activated the audio session.
   bool has_configured_session_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_DEVICE_IOS_AUDIO_DEVICE_IOS_H_