[ObjC ARC] Converts ios/chrome/common to ARC

ios/chrome/common/string_util.mm

 // Copyright 2013 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.
 
 #include "ios/chrome/common/string_util.h"
 
 #import <UIKit/UIKit.h>
 
 #include "base/logging.h"
 #include "base/mac/scoped_block.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 typedef BOOL (^ArrayFilterProcedure)(id object, NSUInteger index, BOOL* stop);
 typedef NSString* (^SubstringExtractionProcedure)(NSUInteger);
 }
 
 NSString* ParseStringWithLink(NSString* text, NSRange* out_link_range) {
   // Find the range within |text| and create a substring without the link tags.
   NSRange begin_range = [text rangeOfString:@"BEGIN_LINK[ \t]*"
                                     options:NSRegularExpressionSearch];
   NSRange link_text_range = NSMakeRange(NSNotFound, 0);
@@ skipping 144 matching lines @@
       else {
         substring = getSubstring.get()(characters - increment);
         break;  // Growing the string, found the right size.
       }
     }
     prevWidth = thisWidth;
   } while (characters > 0 && characters < [string length]);
 
   return substring;
 }