Add video codec setting to AppRTCMobile on iOS.

List items in settings menu no longer stay selected. Checkmarks are now
added to the selected options before the view appears.

BUG=webrtc:7316
TBR=denicija

Review-Url: https://codereview.webrtc.org/2735303004
Cr-Commit-Position: refs/heads/master@{#17296}
diff --git a/webrtc/examples/objc/AppRTCMobile/ios/ARDSettingsStore.h b/webrtc/examples/objc/AppRTCMobile/ios/ARDSettingsStore.h
index 69e10e3..b82ec70 100644
--- a/webrtc/examples/objc/AppRTCMobile/ios/ARDSettingsStore.h
+++ b/webrtc/examples/objc/AppRTCMobile/ios/ARDSettingsStore.h
@@ -19,6 +19,8 @@
  */
 @interface ARDSettingsStore : NSObject
 
+@property(nonatomic) NSString* videoCodec;
+
 /**
  * Returns current video resolution media constraint string stored in the store.
  */