Add video codec setting to AppRTCMobile on iOS.

webrtc/examples/objc/AppRTCMobile/ARDAppClient.h

Index: webrtc/examples/objc/AppRTCMobile/ARDAppClient.h
diff --git a/webrtc/examples/objc/AppRTCMobile/ARDAppClient.h b/webrtc/examples/objc/AppRTCMobile/ARDAppClient.h
index 60ef70071c38117e8b255a3538262852736b9274..0feb01586aab2a0760267f591c3012d6a477886b 100644
--- a/webrtc/examples/objc/AppRTCMobile/ARDAppClient.h
+++ b/webrtc/examples/objc/AppRTCMobile/ARDAppClient.h
@@ -60,7 +60,8 @@ typedef NS_ENUM(NSInteger, ARDAppClientState) {
 @property(nonatomic, weak) id<ARDAppClientDelegate> delegate;
 // Convenience constructor since all expected use cases will need a delegate
 // in order to receive remote tracks.
-- (instancetype)initWithDelegate:(id<ARDAppClientDelegate>)delegate;
+- (instancetype)initWithDelegate:(id<ARDAppClientDelegate>)delegate
+                preferVideoCodec:(NSString*)codec;

[daniela-webrtc, 2017/03/20 13:10:06]

NSString* -> NSString *

[daniela-webrtc, 2017/03/20 13:10:06]

I don't think this is needed as early as the init?
It would be nice to pass all settings the same way i.e either in the initializer
or set as parameters like the media constraints and the bitrate are currently
set.
Having parameters will enable reset of settings when the (ARDApp)client is
cached and not recreated all the time.

 
 // Sets camera constraints.
 - (void)setCameraConstraints:(RTCMediaConstraints *)mediaConstraints;