Delete chrome_plugin_messages.h which is no longer used

ipc/ipc_message_utils.h

 // 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.
 
 #ifndef IPC_IPC_MESSAGE_UTILS_H_
 #define IPC_IPC_MESSAGE_UTILS_H_
 #pragma once
 
 #include <algorithm>
 #include <map>
@@ skipping 75 matching lines @@
   DragMsgStart,
   PrintMsgStart,
   SpellCheckMsgStart,
   ExtensionMsgStart,
   VideoCaptureMsgStart,
   QuotaMsgStart,
   IconMsgStart,
   TextInputClientMsgStart,
   ChromeUtilityMsgStart,
   MediaStreamMsgStart,
-  ChromePluginMsgStart,
   ChromeBenchmarkingMsgStart,
   IntentsMsgStart,
   JavaBridgeMsgStart,
   GamepadMsgStart,
   ShellMsgStart,
   AccessibilityMsgStart,
   PrerenderMsgStart,
   ChromotingMsgStart,
   LastIPCMsgStart      // Must come last.
 };
@@ skipping 1058 matching lines @@
     ReplyParam p(a, b, c, d, e);
     WriteParam(reply, p);
   }
 };
 
 //-----------------------------------------------------------------------------
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_MESSAGE_UTILS_H_