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

ipc/ipc_message_utils.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 "ipc/ipc_message_utils.h"
 
 #include "base/file_path.h"
 #include "base/json/json_writer.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/nullable_string16.h"
@@ skipping 80 matching lines @@
       m->WriteData(binary->GetBuffer(), static_cast<int>(binary->GetSize()));
       break;
     }
     case Value::TYPE_DICTIONARY: {
       const DictionaryValue* dict = static_cast<const DictionaryValue*>(value);
 
       WriteParam(m, static_cast<int>(dict->size()));
 
       for (DictionaryValue::key_iterator it = dict->begin_keys();
            it != dict->end_keys(); ++it) {
-        Value* subval;
+        const Value* subval;
         if (dict->GetWithoutPathExpansion(*it, &subval)) {
           WriteParam(m, *it);
           WriteValue(m, subval, recursion + 1);
         } else {
           NOTREACHED() << "DictionaryValue iterators are filthy liars.";
         }
       }
       break;
     }
     case Value::TYPE_LIST: {
@@ skipping 723 matching lines @@
   return result;
 }
 
 void ParamTraits<MSG>::Log(const param_type& p, std::string* l) {
   l->append("<MSG>");
 }
 
 #endif  // OS_WIN
 
 }  // namespace IPC