iOS:Add loopback launch argument functionality in AppRTCMobile.

It will enable us to start immediate loopback just by passing
the "loopback" string, as argument when launching.
Usefull for testing and command line profiling.

BUG=NONE

Review-Url: https://codereview.webrtc.org/2777983004
Cr-Commit-Position: refs/heads/master@{#17426}

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

@@ -304,14 +304,8 @@ static CGFloat const kCallControlMargin = 8;
 }
 
 - (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
+               didInputRoom:_roomText.roomText
                  isLoopback:_loopbackSwitch.isOn
                 isAudioOnly:_audioOnlySwitch.isOn
           shouldMakeAecDump:_aecdumpSwitch.isOn

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

@@ -25,6 +25,9 @@
 
 static NSString *const barButtonImageString = @"ic_settings_black_24dp.png";
 
+// Launch argument to be passed to indicate that the app should start loopback immediatly
+static NSString *const loopbackLaunchProcessArgument = @"loopback";
+
 @interface ARDMainViewController () <
     ARDMainViewDelegate,
     ARDVideoCallViewControllerDelegate,
@@ -37,6 +40,19 @@ static NSString *const barButtonImageString = @"ic_settings_black_24dp.png";
   BOOL _useManualAudio;
 }
 
+- (void)viewDidLoad {
+  [super viewDidLoad];
+  if ([[[NSProcessInfo processInfo] arguments] containsObject:loopbackLaunchProcessArgument]) {
+    [self mainView:nil
+                 didInputRoom:@""
+                   isLoopback:YES
+                  isAudioOnly:NO
+            shouldMakeAecDump:NO
+        shouldUseLevelControl:NO
+               useManualAudio:NO];
+  }
+}
+
 - (void)loadView {
   self.title = @"AppRTC Mobile";
   _mainView = [[ARDMainView alloc] initWithFrame:CGRectZero];
@@ -66,6 +82,12 @@ static NSString *const barButtonImageString = @"ic_settings_black_24dp.png";
   self.navigationItem.rightBarButtonItem = settingsButton;
 }
 
++ (NSString *)loopbackRoomString {
+  NSString *loopbackRoomString =
+      [[NSUUID UUID].UUIDString stringByReplacingOccurrencesOfString:@"-" withString:@""];
+  return loopbackRoomString;
+}
+
 #pragma mark - ARDMainViewDelegate
 
 - (void)mainView:(ARDMainView *)mainView
@@ -76,9 +98,14 @@ static NSString *const barButtonImageString = @"ic_settings_black_24dp.png";
     shouldUseLevelControl:(BOOL)shouldUseLevelControl
            useManualAudio:(BOOL)useManualAudio {
   if (!room.length) {
+    if (isLoopback) {
+      // If this is a loopback call, allow a generated room name.
+      room = [[self class] loopbackRoomString];
+    } else {
       [self showAlertWithMessage:@"Missing room name."];
       return;
     }
+  }
   // Trim whitespaces.
   NSCharacterSet *whitespaceSet = [NSCharacterSet whitespaceCharacterSet];
   NSString *trimmedRoom = [room stringByTrimmingCharactersInSet:whitespaceSet];