Add video codec setting to AppRTCMobile on iOS.

webrtc/examples/objc/AppRTCMobile/ios/ARDSettingsStore.h

 /*
  *  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 <Foundation/Foundation.h>
 
 NS_ASSUME_NONNULL_BEGIN
 
 /**
  * Light-weight persistent store for user settings.
  *
  * It will persist between application launches and application updates.
  */
 @interface ARDSettingsStore : NSObject
 
+@property(nonatomic) NSString* videoCodec;

[daniela-webrtc, 2017/03/20 13:10:07]

NSString* -> NSString *

+
 /**
  * Returns current video resolution media constraint string stored in the store.
  */
 - (nullable NSString *)videoResolutionConstraints;
 
 /**
  * Stores the provided value as video resolution media constraint.
  * @param value the string to be stored
  */
 - (void)setVideoResolutionConstraints:(NSString *)value;
 
 /**
  * Returns current max bitrate number stored in the store.
  */
 - (nullable NSNumber *)maxBitrate;
 
 /**
  * Stores the provided value as maximum bitrate setting.
  * @param value the number to be stored
  */
 - (void)setMaxBitrate:(nullable NSNumber *)value;
 
 @end
 NS_ASSUME_NONNULL_END