Add option --dump-render-tree to content_shell to dump the render tree as text.

ipc/ipc_message_utils.h

 // Copyright (c) 2011 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 IPC_IPC_MESSAGE_UTILS_H_
 #define IPC_IPC_MESSAGE_UTILS_H_
 #pragma once
 
 #include <algorithm>
 #include <map>
@@ skipping 80 matching lines @@
   QuotaMsgStart,
   IconMsgStart,
   TextInputClientMsgStart,
   ChromeUtilityMsgStart,
   MediaStreamMsgStart,
   ChromePluginMsgStart,
   ChromeBenchmarkingMsgStart,
   IntentsMsgStart,
   JavaBridgeMsgStart,
   GamepadMsgStart,
+  ShellMsgStart,
   LastIPCMsgStart      // Must come last.
 };
 
 class FilePath;
 class NullableString16;
 
 namespace base {
 class DictionaryValue;
 class ListValue;
 class Time;
@@ skipping 1027 matching lines @@
     ReplyParam p(a, b, c, d, e);
     WriteParam(reply, p);
   }
 };
 
 //-----------------------------------------------------------------------------
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_MESSAGE_UTILS_H_