Explicitly @synthesize ObjC @properties

This is required after https://code.google.com/p/gyp/source/detail?r=1768
turned on -Wobjc-missing-property-synthesis for ninja builds (until then it
was only enabled for xcode builds) to allow chromium_deps to roll in
webrtc/DEPS.

BUG=2560
R=kjellander@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/3089004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5047 4adac7df-926f-26a2-2b94-8c16560cd09d

talk/examples/ios/AppRTCDemo/APPRTCViewController.m

@@ -33,6 +33,10 @@
 
 @implementation APPRTCViewController
 
+@synthesize textField = _textField;
+@synthesize textInstructions = _textInstructions;
+@synthesize textOutput = _textOutput;
+
 - (void)viewDidLoad {
   [super viewDidLoad];
   self.textField.delegate = self;