Provide isAudioEnabled flag to control audio unit.

webrtc/modules/audio_device/ios/audio_session_observer.h

Index: webrtc/modules/audio_device/ios/audio_session_observer.h
diff --git a/webrtc/modules/audio_device/ios/audio_session_observer.h b/webrtc/modules/audio_device/ios/audio_session_observer.h
index 6c4a9cd9e27f5679889fe1e600ca059bccbb89f2..def8c2322b00d0471b75ef8bf8fc8e13d2fa19eb 100644
--- a/webrtc/modules/audio_device/ios/audio_session_observer.h
+++ b/webrtc/modules/audio_device/ios/audio_session_observer.h
@@ -28,8 +28,8 @@ class AudioSessionObserver {
   // Called when audio route changes.
   virtual void OnValidRouteChange() = 0;
 
-  // Called when audio session has been configured for WebRTC.
-  virtual void OnConfiguredForWebRTC() = 0;
+  // Called when the ability to play or record changes.
+  virtual void OnCanPlayOrRecordChange(bool can_play_or_record) = 0;
 
  protected:
   virtual ~AudioSessionObserver() {}