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 {
+  RTCInitFieldTrials(RTCFieldTrialOptionsSendSideBwe);
   [RTCPeerConnectionFactory initializeSSL];
   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