iOS:Add loopback launch argument functionality in AppRTCMobile.

webrtc/examples/objc/AppRTCMobile/ios/ARDMainView.m

 /*
  *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 286 matching lines @@
                       forState:UIControlStateNormal];
     [_audioLoopButton sizeToFit];
   }
 }
 
 - (void)onToggleAudioLoop:(id)sender {
   [_delegate mainViewDidToggleAudioLoop:self];
 }
 
 - (void)onStartCall:(id)sender {
-  NSString *room = _roomText.roomText;
-  // If this is a loopback call, allow a generated room name.
-  if (!room.length && _loopbackSwitch.isOn) {
-    room = [[NSUUID UUID] UUIDString];
-  }
-  room = [room stringByReplacingOccurrencesOfString:@"-" withString:@""];
   [_delegate mainView:self
-                didInputRoom:room
-                  isLoopback:_loopbackSwitch.isOn
-                 isAudioOnly:_audioOnlySwitch.isOn
-           shouldMakeAecDump:_aecdumpSwitch.isOn
-       shouldUseLevelControl:_levelControlSwitch.isOn
-              useManualAudio:_useManualAudioSwitch.isOn];
+               didInputRoom:_roomText.roomText
+                 isLoopback:_loopbackSwitch.isOn
+                isAudioOnly:_audioOnlySwitch.isOn
+          shouldMakeAecDump:_aecdumpSwitch.isOn
+      shouldUseLevelControl:_levelControlSwitch.isOn
+             useManualAudio:_useManualAudioSwitch.isOn];
 }
 
 @end