Loopback and audio only mode.

Adds a loopback button that will connect to itself by simulating another client connection to the web socket server.

Adds an audio only mode switch.

BUG=

Review URL: https://codereview.webrtc.org/1334003002

Cr-Commit-Position: refs/heads/master@{#10153}
diff --git a/webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m b/webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m
index 674c97b..8de6b95 100644
--- a/webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m
+++ b/webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m
@@ -31,10 +31,14 @@
 
 @synthesize videoCallView = _videoCallView;
 
-- (instancetype)initForRoom:(NSString *)room {
+- (instancetype)initForRoom:(NSString *)room
+                 isLoopback:(BOOL)isLoopback
+                isAudioOnly:(BOOL)isAudioOnly {
   if (self = [super init]) {
     _client = [[ARDAppClient alloc] initWithDelegate:self];
-    [_client connectToRoomWithId:room options:nil];
+    [_client connectToRoomWithId:room
+                      isLoopback:isLoopback
+                     isAudioOnly:isAudioOnly];
   }
   return self;
 }