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

ios/chrome/browser/passwords/js_password_manager.mm

 // Copyright 2012 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/passwords/js_password_manager.h"
 
 #include "base/json/string_escape.h"
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 // Sanitizes |JSONString| and wraps it in quotes so it can be injected safely in
 // JavaScript.
 NSString* JSONEscape(NSString* JSONString) {
   return base::SysUTF8ToNSString(
       base::GetQuotedJSONString(base::SysNSStringToUTF8(JSONString)));
 }
 }  // namespace
 
 @interface JsPasswordManager ()
@@ skipping 72 matching lines @@
 - (void)evaluateExtraScript:(NSString*)script
           completionHandler:(void (^)(NSString*))completionHandler {
   DCHECK(completionHandler);
   NSString* JS = [[self injectionContent] stringByAppendingString:script];
   [self executeJavaScript:JS completionHandler:^(id result, NSError*) {
     completionHandler(base::mac::ObjCCastStrict<NSString>(result));
   }];
 }
 
 @end