GN: Add targets for AppRTCDemo on Mac+iOS

BUG=webrtc:6022
NOTRY=True

Review-Url: https://codereview.webrtc.org/2211413003
Cr-Commit-Position: refs/heads/master@{#13666}

webrtc/examples/objc/AppRTCDemo/mac/APPRTCViewController.m

@@ -47,12 +47,14 @@ static NSUInteger const kLogViewHeight = 280;
   NSTextField* _roomLabel;
   NSTextField* _roomField;
   NSTextView* _logView;
-  RTCNSGLVideoView* _localVideoView;
-  RTCNSGLVideoView* _remoteVideoView;
   CGSize _localVideoSize;
   CGSize _remoteVideoSize;
 }
 
+@synthesize delegate = _delegate;
+@synthesize localVideoView = _localVideoView;
+@synthesize remoteVideoView = _remoteVideoView;
+
 + (BOOL)requiresConstraintBasedLayout {
   return YES;
 }