Update iOS AppRTCDemo to use the updated Objective-C API.

webrtc/examples/objc/AppRTCDemo/ios/ARDVideoCallViewController.m

 /*
  *  Copyright 2015 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 "ARDVideoCallViewController.h"
 
-#import "RTCAVFoundationVideoSource.h"
-#import "RTCLogging.h"
+#import "webrtc/api/objc/RTCAVFoundationVideoSource.h"
+#import "webrtc/base/objc/RTCLogging.h"
 
 #import "ARDAppClient.h"
 #import "ARDVideoCallView.h"
 
 @interface ARDVideoCallViewController () <ARDAppClientDelegate,
     ARDVideoCallViewDelegate>
 @property(nonatomic, strong) RTCVideoTrack *localVideoTrack;
 @property(nonatomic, strong) RTCVideoTrack *remoteVideoTrack;
 @property(nonatomic, readonly) ARDVideoCallView *videoCallView;
 @end
@@ skipping 112 matching lines @@
   }
   _videoCallView.localVideoView.captureSession = source.captureSession;
 }
 
 - (void)setRemoteVideoTrack:(RTCVideoTrack *)remoteVideoTrack {
   if (_remoteVideoTrack == remoteVideoTrack) {
     return;
   }
   [_remoteVideoTrack removeRenderer:_videoCallView.remoteVideoView];
   _remoteVideoTrack = nil;
   [_videoCallView.remoteVideoView renderFrame:nil];

[hjon_webrtc, 2016/02/12 18:50:58]

Is this line needed? The updated API is currently assuming this is called with a
nonnull value, and I'm not certain if the API or this line needs to be changed.

   _remoteVideoTrack = remoteVideoTrack;
   [_remoteVideoTrack addRenderer:_videoCallView.remoteVideoView];
 }
 
 - (void)hangup {
   self.remoteVideoTrack = nil;
   self.localVideoTrack = nil;
   [_client disconnect];
   if (![self isBeingDismissed]) {
     [self.presentingViewController dismissViewControllerAnimated:YES
@@ skipping 29 matching lines @@
 - (void)showAlertWithMessage:(NSString*)message {
   UIAlertView* alertView = [[UIAlertView alloc] initWithTitle:nil
                                                       message:message
                                                      delegate:nil
                                             cancelButtonTitle:@"OK"
                                             otherButtonTitles:nil];
   [alertView show];
 }
 
 @end