Update //third_party/protobuf to version 3.

third_party/protobuf/objectivec/Tests/iOSTestHarness/AppDelegate.m

+#import <UIKit/UIKit.h>
+
+@interface AppDelegate : UIResponder <UIApplicationDelegate>
+@property (strong, nonatomic) UIWindow *window;
+@end
+
+@implementation AppDelegate
+
+@synthesize window;
+
+- (BOOL)application:(UIApplication *)application
+    didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
+  #pragma unused (application, launchOptions)
+
+  self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
+  self.window.backgroundColor = [UIColor whiteColor];
+  [self.window makeKeyAndVisible];
+  self.window.rootViewController = [[UIViewController alloc] init];
+
+  UILabel *label =
+      [[UILabel alloc] initWithFrame:CGRectMake(0, 200, CGRectGetWidth(self.window.frame), 40)];
+  label.text = @"Protocol Buffer Test Harness";
+  label.textAlignment = NSTextAlignmentCenter;
+  [self.window addSubview:label];
+
+  return YES;
+}
+
+@end
+
+int main(int argc, char * argv[]) {
+  @autoreleasepool {
+    return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
+  }
+}