Use RTCAudioSessionDelegate in AudioDeviceIOS.

webrtc/modules/audio_device/ios/audio_device_ios.h

Index: webrtc/modules/audio_device/ios/audio_device_ios.h
diff --git a/webrtc/modules/audio_device/ios/audio_device_ios.h b/webrtc/modules/audio_device/ios/audio_device_ios.h
index 73208864d245a71d157138179004ed3dc6d275a3..82163e3fbdabee19c23128a5c20ddf11bf041404 100644
--- a/webrtc/modules/audio_device/ios/audio_device_ios.h
+++ b/webrtc/modules/audio_device/ios/audio_device_ios.h
@@ -15,9 +15,12 @@
 
 #include <AudioUnit/AudioUnit.h>
 
+#include "webrtc/base/objc/RTCMacros.h"
 #include "webrtc/base/thread_checker.h"
 #include "webrtc/modules/audio_device/audio_device_generic.h"
 
+RTC_FWD_DECL_OBJC_CLASS(RTCAudioSessionDelegateAdapter);
+
 namespace webrtc {
 
 class FineAudioBuffer;
@@ -151,16 +154,16 @@ class AudioDeviceIOS : public AudioDeviceGeneric {
   void ClearRecordingWarning() override {}
   void ClearRecordingError() override {}
 
+  // These methods should be called in response to audio events.

[henrika_webrtc, 2016/03/15 08:53:44]

Any restrictions on the calling thread?

[tkchin_webrtc, 2016/03/15 20:14:58]

Done.

+  void OnInterruptionBegin();
+  void OnInterruptionEnd();
+  void OnValidRouteChange();
+
  private:
   // Uses current |playout_parameters_| and |record_parameters_| to inform the
   // audio device buffer (ADB) about our internal audio parameters.
   void UpdateAudioDeviceBuffer();
 
-  // Registers observers for the AVAudioSessionRouteChangeNotification and
-  // AVAudioSessionInterruptionNotification notifications.
-  void RegisterNotificationObservers();
-  void UnregisterNotificationObservers();
-
   // Since the preferred audio parameters are only hints to the OS, the actual
   // values may be different once the AVAudioSession has been activated.
   // This method asks for the current hardware parameters and takes actions
@@ -286,9 +289,11 @@ class AudioDeviceIOS : public AudioDeviceGeneric {
   // Set to true after successful call to InitPlayout(), false otherwise.
   bool play_is_initialized_;
 
+  // Set to true if audio session is interrupted, false otherwise.
+  bool is_interrupted_;
+
   // Audio interruption observer instance.
-  void* audio_interruption_observer_;
-  void* route_change_observer_;
+  RTCAudioSessionDelegateAdapter* audio_session_observer_;
 
   // Contains the audio data format specification for a stream of audio.
   AudioStreamBasicDescription application_format_;