Converts parts of ios/web to ARC

ios/web/url_scheme_util.mm

 // Copyright 2014 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/web/public/url_scheme_util.h"
 
 #import <Foundation/Foundation.h>
 
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 bool UrlHasWebScheme(const GURL& url) {
   return url.SchemeIs(url::kHttpScheme) ||
          url.SchemeIs(url::kHttpsScheme) ||
          url.SchemeIs(url::kDataScheme);
 }
 
 bool UrlHasWebScheme(NSURL* url) {
   NSString* scheme = [url scheme];
   if (![scheme length])
     return false;
 
   // Use the GURL implementation, but with a scheme-only URL to avoid
   // unnecessary parsing in GURL construction.
   NSString* schemeURLString = [scheme stringByAppendingString:@":"];
   GURL gurl([schemeURLString UTF8String]);
   return UrlHasWebScheme(gurl);
 }
 
 }  // namespace web