Provide isAudioEnabled flag to control audio unit.

webrtc/modules/audio_device/ios/voice_processing_audio_unit.h

 /*
  *  Copyright 2016 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 15 matching lines @@
                                          AudioBufferList* io_data) = 0;
 
   // Callback function called on a real-time priority I/O thread from the audio
   // unit. This method is used to provide audio samples to the audio unit.
   virtual OSStatus OnGetPlayoutData(AudioUnitRenderActionFlags* io_action_flags,
                                     const AudioTimeStamp* time_stamp,
                                     UInt32 bus_number,
                                     UInt32 num_frames,
                                     AudioBufferList* io_data) = 0;
 
+  // Callback function called when the sample rate changes.
+  virtual void OnSampleRateChange(float sample_rate) = 0;
+
  protected:
   ~VoiceProcessingAudioUnitObserver() {}
 };
 
 // Convenience class to abstract away the management of a Voice Processing
 // I/O Audio Unit. The Voice Processing I/O unit has the same characteristics
 // as the Remote I/O unit (supports full duplex low-latency audio input and
 // output) and adds AEC for for two-way duplex communication. It also adds AGC,
 // adjustment of voice-processing quality, and muting. Hence, ideal for
 // VoIP applications.
@@ skipping 54 matching lines @@
                                    const AudioTimeStamp* time_stamp,
                                    UInt32 bus_number,
                                    UInt32 num_frames,
                                    AudioBufferList* io_data);
   static OSStatus OnDeliverRecordedData(void* in_ref_con,
                                         AudioUnitRenderActionFlags* flags,
                                         const AudioTimeStamp* time_stamp,
                                         UInt32 bus_number,
                                         UInt32 num_frames,
                                         AudioBufferList* io_data);
+  static void OnSampleRateChange(void* in_ref_con,
+                                 AudioUnit audio_unit,
+                                 AudioUnitPropertyID property_id,
+                                 AudioUnitScope scope,
+                                 AudioUnitElement element);
 
   // Notifies observer that samples are needed for playback.
   OSStatus NotifyGetPlayoutData(AudioUnitRenderActionFlags* flags,
                                 const AudioTimeStamp* time_stamp,
                                 UInt32 bus_number,
                                 UInt32 num_frames,
                                 AudioBufferList* io_data);
   // Notifies observer that recorded samples are available for render.
   OSStatus NotifyDeliverRecordedData(AudioUnitRenderActionFlags* flags,
                                      const AudioTimeStamp* time_stamp,
                                      UInt32 bus_number,
                                      UInt32 num_frames,
                                      AudioBufferList* io_data);
+  // Notifies observer that sample rate has changed.
+  void NotifySampleRateChange(AudioUnit audio_unit,
+                              AudioUnitPropertyID property_id,
+                              AudioUnitScope scope,
+                              AudioUnitElement element);
 
   // Returns the predetermined format with a specific sample rate. See
   // implementation file for details on format.
   AudioStreamBasicDescription GetFormat(Float64 sample_rate) const;
 
   // Deletes the underlying audio unit.
   void DisposeAudioUnit();
 
   VoiceProcessingAudioUnitObserver* observer_;
   AudioUnit vpio_unit_;
   VoiceProcessingAudioUnit::State state_;
 };
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_DEVICE_IOS_VOICE_PROCESSING_AUDIO_UNIT_H_