Enable iOS AppRTCDemo send side BWE.

BUG=

Review URL: https://codereview.webrtc.org/1757173002

Cr-Commit-Position: refs/heads/master@{#11865}

webrtc/base/BUILD.gn

@@ -637,6 +637,8 @@ if (is_ios) {
       "objc/RTCCameraPreviewView.m",
       "objc/RTCDispatcher.h",
       "objc/RTCDispatcher.m",
+      "objc/RTCFieldTrials.h",
+      "objc/RTCFieldTrials.mm",
       "objc/RTCFileLogger.h",
       "objc/RTCFileLogger.mm",
       "objc/RTCLogging.h",

webrtc/base/base.gyp

@@ -36,6 +36,8 @@
             'objc/NSString+StdString.mm',
             'objc/RTCDispatcher.h',
             'objc/RTCDispatcher.m',
+            'objc/RTCFieldTrials.h',
+            'objc/RTCFieldTrials.mm',
             'objc/RTCFileLogger.h',
             'objc/RTCFileLogger.mm',
             'objc/RTCLogging.h',

webrtc/base/objc/RTCFieldTrials.h

@@ -0,0 +1,21 @@
+/*
+ *  Copyright 2016 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.
+ */
+
+#include "webrtc/base/objc/RTCMacros.h"
+
+typedef NS_OPTIONS(NSUInteger, RTCFieldTrialOptions) {
+  RTCFieldTrialOptionsNone = 0,
+  RTCFieldTrialOptionsSendSideBwe = 1 << 0,
+};
+
+/** Must be called before any other call into WebRTC. See:
+ *  webrtc/system_wrappers/include/field_trial_default.h
+ */
+RTC_EXPORT void RTCInitFieldTrials(RTCFieldTrialOptions options);

webrtc/base/objc/RTCFieldTrials.mm

@@ -0,0 +1,37 @@
+/*
+ *  Copyright 2016 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 "webrtc/base/objc/RTCFieldTrials.h"
+
+#include <memory>
+#include "webrtc/system_wrappers/include/field_trial_default.h"
+
+#import <Foundation/Foundation.h>
+#import "webrtc/base/objc/RTCLogging.h"
+
+static NSString * const kRTCEnableSendSideBweString =
+    @"WebRTC-SendSideBwe/Enabled/";
+static std::unique_ptr<char[]> gFieldTrialInitString;
+
+void RTCInitFieldTrials(RTCFieldTrialOptions options) {
+  NSMutableString *fieldTrialInitString = [NSMutableString string];
+  if (options & RTCFieldTrialOptionsSendSideBwe) {
+    [fieldTrialInitString appendString:kRTCEnableSendSideBweString];
+  }
+  size_t len = fieldTrialInitString.length + 1;
+  gFieldTrialInitString.reset(new char[len]);
+  if (![fieldTrialInitString getCString:gFieldTrialInitString.get()
+                              maxLength:len
+                               encoding:NSUTF8StringEncoding]) {
+    RTCLogError(@"Failed to convert field trial string.");
+    return;
+  }
+  webrtc::field_trial::InitFieldTrialsFromString(gFieldTrialInitString.get());
+}

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

@@ -10,6 +10,7 @@
 
 #import "ARDAppDelegate.h"
 
+#import "webrtc/base/objc/RTCFieldTrials.h"
 #import "webrtc/base/objc/RTCTracing.h"
 #import "RTCLogging.h"
 #import "RTCPeerConnectionFactory.h"
@@ -24,6 +25,7 @@
 
 - (BOOL)application:(UIApplication *)application
     didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
+  RTCInitFieldTrials(RTCFieldTrialOptionsSendSideBwe);
   [RTCPeerConnectionFactory initializeSSL];
   RTCSetupInternalTracer();
   _window =  [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];