Provide isAudioEnabled flag to control audio unit.

webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m

Index: webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m
diff --git a/webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m b/webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m
index 80bbb10bb39d4dfe73259fe218280cd870643a4a..d35e1e6b2d0274792d9da8526ca65032731cc065 100644
--- a/webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m
+++ b/webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m
@@ -34,11 +34,14 @@
 }
 
 @synthesize videoCallView = _videoCallView;
+@synthesize delegate = _delegate;
 
 - (instancetype)initForRoom:(NSString *)room
                  isLoopback:(BOOL)isLoopback
-                isAudioOnly:(BOOL)isAudioOnly {
+                isAudioOnly:(BOOL)isAudioOnly
+                   delegate:(id<ARDVideoCallViewControllerDelegate>)delegate {
   if (self = [super init]) {
+    _delegate = delegate;
     _client = [[ARDAppClient alloc] initWithDelegate:self];
     [_client connectToRoomWithId:room
                       isLoopback:isLoopback
@@ -177,10 +180,7 @@
   self.remoteVideoTrack = nil;
   self.localVideoTrack = nil;
   [_client disconnect];
-  if (![self isBeingDismissed]) {
-    [self.presentingViewController dismissViewControllerAnimated:YES
-                                                      completion:nil];
-  }
+  [_delegate viewControllerDidFinish:self];
 }
 
 - (void)switchCamera {