Enable iOS AppRTCDemo send side BWE.

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

 /*
  *  Copyright 2013 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.
  */
 
 #import "ARDAppDelegate.h"
 
+#import "webrtc/base/objc/RTCFieldTrials.h"
 #import "webrtc/base/objc/RTCTracing.h"
 #import "RTCLogging.h"
 #import "RTCPeerConnectionFactory.h"
 
 #import "ARDMainViewController.h"
 
 @implementation ARDAppDelegate {
   UIWindow *_window;
 }
 
 #pragma mark - UIApplicationDelegate methods
 
 - (BOOL)application:(UIApplication *)application
     didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
   [RTCPeerConnectionFactory initializeSSL];
+  RTCInitFieldTrials(RTCFieldTrialOptionsSendSideBwe);

[Chuck, 2016/03/03 14:37:59]

Just a question, the comment says this must be called before any other WebRTC
method, but this call is after RTCPeerConnectioNFactory initializeSSL.

[tkchin_webrtc, 2016/03/03 17:58:41]

Yeah, that actually isn't a "WebRTC" method. It just loads/initializes the SSL
library.
The reason it needs to be called before WebRTC stuff is because options for
field trials get loaded on init, so if you call it after init it does nothing.
Essentially as long as you init field trials before you create a
peerconnectionfactory instance you should be fine.
Unless we decide to add a field trial to the SSL init method.
Anyway, moving it up to prevent confusion.

   RTCSetupInternalTracer();
   _window =  [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
   [_window makeKeyAndVisible];
   ARDMainViewController *viewController = [[ARDMainViewController alloc] init];
   _window.rootViewController = viewController;
 
 #if defined(NDEBUG)
   // In debug builds the default level is LS_INFO and in non-debug builds it is
   // disabled. Continue to log to console in non-debug builds, but only
   // warnings and errors.
   RTCSetMinDebugLogLevel(kRTCLoggingSeverityWarning);
 #endif
 
   return YES;
 }
 
 - (void)applicationWillResignActive:(UIApplication *)application {
   ARDMainViewController *viewController =
       (ARDMainViewController *)_window.rootViewController;
   [viewController applicationWillResignActive:application];
 }
 
 - (void)applicationWillTerminate:(UIApplication *)application {
   RTCShutdownInternalTracer();
   [RTCPeerConnectionFactory deinitializeSSL];
 }
 
 @end