[ObjC ARC] Converts ios/chrome/browser:browser to ARC.

ios/chrome/browser/open_url_util.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/open_url_util.h"
 
 #import <UIKit/UIKit.h>
 
 #include "base/ios/ios_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 void OpenUrlWithCompletionHandler(NSURL* url,
                                   void (^completion_handler)(BOOL success)) {
   if (base::ios::IsRunningOnIOS10OrLater()) {
     [[UIApplication sharedApplication] openURL:url
                                        options:@{}
                              completionHandler:completion_handler];
   } else {
     BOOL result = [[UIApplication sharedApplication] openURL:url];
     if (!completion_handler)
       return;
     dispatch_async(dispatch_get_main_queue(), ^{
       completion_handler(result);
     });
   }
 }