Add video codec setting to AppRTCMobile on iOS.

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

Index: webrtc/examples/objc/AppRTCMobile/ios/ARDSettingsStore.m
diff --git a/webrtc/examples/objc/AppRTCMobile/ios/ARDSettingsStore.m b/webrtc/examples/objc/AppRTCMobile/ios/ARDSettingsStore.m
index fd396b53815bacf2f4e144d7d0a3e108d1f60600..c05df4416a5253ca682dfdfc2ca2af8a56e28084 100644
--- a/webrtc/examples/objc/AppRTCMobile/ios/ARDSettingsStore.m
+++ b/webrtc/examples/objc/AppRTCMobile/ios/ARDSettingsStore.m
@@ -11,6 +11,7 @@
 #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
@@ -38,6 +39,15 @@ NS_ASSUME_NONNULL_BEGIN
   [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];
 }