Provide isAudioEnabled flag to control audio unit.

webrtc/modules/audio_device/ios/objc/RTCAudioSessionDelegateAdapter.mm

Index: webrtc/modules/audio_device/ios/objc/RTCAudioSessionDelegateAdapter.mm
diff --git a/webrtc/modules/audio_device/ios/objc/RTCAudioSessionDelegateAdapter.mm b/webrtc/modules/audio_device/ios/objc/RTCAudioSessionDelegateAdapter.mm
index 2df502e0872de4977ed50a16597877058fddaece..b554e51ece05bcf240e02a8436b465b3d16cc479 100644
--- a/webrtc/modules/audio_device/ios/objc/RTCAudioSessionDelegateAdapter.mm
+++ b/webrtc/modules/audio_device/ios/objc/RTCAudioSessionDelegateAdapter.mm
@@ -70,14 +70,15 @@
 - (void)audioSessionMediaServicesWereReset:(RTCAudioSession *)session {
 }
 
-- (void)audioSessionShouldConfigure:(RTCAudioSession *)session {
+- (void)audioSession:(RTCAudioSession *)session
+    didChangeCanPlayOrRecord:(BOOL)canPlayOrRecord {
+  _observer->OnCanPlayOrRecordChange(canPlayOrRecord);
 }
 
-- (void)audioSessionShouldUnconfigure:(RTCAudioSession *)session {
+- (void)audioSessionDidStartPlayOrRecord:(RTCAudioSession *)session {
 }
 
-- (void)audioSessionDidConfigure:(RTCAudioSession *)session {
-  _observer->OnConfiguredForWebRTC();
+- (void)audioSessionDidStopPlayOrRecord:(RTCAudioSession *)session {
 }
 
 @end