Correct const accessors in base/values.(h|cc)

chrome/service/cloud_print/print_system_cups.cc

 // Copyright (c) 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.
 
 #include "chrome/service/cloud_print/print_system.h"
 
 #include <cups/cups.h>
 #include <dlfcn.h>
 #include <errno.h>
 #include <pthread.h>
@@ skipping 416 matching lines @@
     bool notify_delete = true;
     if (print_system_settings->GetBoolean(kCUPSNotifyDelete, &notify_delete))
       notify_delete_ = notify_delete;
   }
 
   InitPrintBackends(print_system_settings);
 }
 
 void PrintSystemCUPS::InitPrintBackends(
     const DictionaryValue* print_system_settings) {
-  ListValue* url_list;
+  const ListValue* url_list;
   if (print_system_settings &&
       print_system_settings->GetList(kCUPSPrintServerURLs, &url_list)) {
     for (size_t i = 0; i < url_list->GetSize(); i++) {
       std::string print_server_url;
       if (url_list->GetString(i, &print_server_url))
         AddPrintServer(print_server_url);
     }
   }
 
   // If server list is empty, use default print server.
@@ skipping 417 matching lines @@
 
 void PrintSystemCUPS::RunCapsCallback(
     const PrinterCapsAndDefaultsCallback& callback,
     bool succeeded,
     const std::string& printer_name,
     const printing::PrinterCapsAndDefaults& printer_info) {
   callback.Run(succeeded, printer_name, printer_info);
 }
 
 }  // namespace cloud_print