[ARC] Converts part of ios/web to ARC.

ios/web/web_state/js/page_script_util.mm

 // Copyright 2015 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/web_state/js/page_script_util.h"
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/mac/bundle_locations.h"
 #include "base/strings/sys_string_conversions.h"
 #include "ios/web/public/web_client.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 NSString* GetPageScript(NSString* script_file_name) {
   DCHECK(script_file_name);
   NSString* path =
       [base::mac::FrameworkBundle() pathForResource:script_file_name
                                              ofType:@"js"];
   DCHECK(path) << "Script file not found: "
                << base::SysNSStringToUTF8(script_file_name) << ".js";
   NSError* error = nil;
@@ skipping 17 matching lines @@
   // __gCrWeb.windowId variable and will break the ability to send messages from
   // JS to the native code. Wrapping injected script into "if (!injected)" check
   // prevents multiple injections into the same page.
   NSString* kScriptTemplate = @"if (typeof __gCrWeb !== 'object') { %@; %@ }";
   return [NSString stringWithFormat:kScriptTemplate,
                                     GetPageScript(@"web_bundle"),
                                     embedder_page_script];
 }
 
 }  // namespace web