fix uninitialized variable warning for vs2012 compilation

net/http/http_request_headers.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 "net/http/http_request_headers.h"
 
 #include "base/logging.h"
 #include "base/stringprintf.h"
 #include "base/string_split.h"
 #include "base/string_util.h"
@@ skipping 189 matching lines @@
   return dict;
 }
 
 // static
 bool HttpRequestHeaders::FromNetLogParam(const base::Value* event_param,
                                          HttpRequestHeaders* headers,
                                          std::string* request_line) {
   headers->Clear();
   *request_line = "";
 
-  const base::DictionaryValue* dict;
-  const base::ListValue* header_list;
+  const base::DictionaryValue* dict = NULL;
+  const base::ListValue* header_list = NULL;
 
   if (!event_param ||
       !event_param->GetAsDictionary(&dict) ||
       !dict->GetList("headers", &header_list) ||
       !dict->GetString("line", request_line)) {
     return false;
   }
 
   for (base::ListValue::const_iterator it = header_list->begin();
        it != header_list->end();
@@ skipping 27 matching lines @@
        it != headers_.end(); ++it) {
     if (key.length() == it->key.length() &&
         !base::strncasecmp(key.data(), it->key.data(), key.length()))
       return it;
   }
 
   return headers_.end();
 }
 
 }  // namespace net