DevTools: implement basic handshake for remote debugging.

net/server/http_server_request_info.h

 // Copyright (c) 2010 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.
 
 #ifndef NET_SERVER_HTTP_SERVER_REQUEST_INFO_H_
 #define NET_SERVER_HTTP_SERVER_REQUEST_INFO_H_
 
 #include <string>
 #include <map>
 
@@ skipping 11 matching lines @@
   std::string method;
 
   // Request line.
   std::string path;
 
   // Request data.
   std::string data;
 
   // A map of the names -> values for HTTP headers.
   typedef std::map<std::string, std::string> HeadersMap;
-  HeadersMap headers;
+  mutable HeadersMap headers;
 };
 
 #endif  // NET_SERVER_HTTP_SERVER_REQUEST_INFO_H_