Add video codec setting to AppRTCMobile on iOS.

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

 /*
  *  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 "ARDSettingsStore.h"
 
 static NSString *const kMediaConstraintsKey = @"rtc_video_resolution_media_constraints_key";
+static NSString *const kVideoCodecKey = @"rtc_video_codec_key";
 static NSString *const kBitrateKey = @"rtc_max_bitrate_key";
 
 NS_ASSUME_NONNULL_BEGIN
 @interface ARDSettingsStore () {
   NSUserDefaults *_storage;
 }
 @property(nonatomic, strong) NSUserDefaults *storage;
 @end
 
 @implementation ARDSettingsStore
 
 - (NSUserDefaults *)storage {
   if (!_storage) {
     _storage = [NSUserDefaults standardUserDefaults];
   }
   return _storage;
 }
 
 - (nullable NSString *)videoResolutionConstraints {
   return [self.storage objectForKey:kMediaConstraintsKey];
 }
 
 - (void)setVideoResolutionConstraints:(NSString *)constraintsString {
   [self.storage setObject:constraintsString forKey:kMediaConstraintsKey];
   [self.storage synchronize];
 }
 
+- (NSString *)videoCodec {
+  return [self.storage objectForKey:kVideoCodecKey];
+}
+
+- (void)setVideoCodec:(NSString *)videoCodec {
+  [self.storage setObject:videoCodec forKey:kVideoCodecKey];
+  [self.storage synchronize];
+}
+
 - (nullable NSNumber *)maxBitrate {
   return [self.storage objectForKey:kBitrateKey];
 }
 
 - (void)setMaxBitrate:(nullable NSNumber *)value {
   [self.storage setObject:value forKey:kBitrateKey];
   [self.storage synchronize];
 }
 
 @end
 NS_ASSUME_NONNULL_END