Generate param traits even when shared by mutliple message files.

chrome/common/automation_messages.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.
 
 // Multiply-included message file, no traditional include guard.
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "chrome/common/automation_constants.h"
 #include "chrome/common/automation_events.h"
+#include "chrome/common/common_param_traits.h"
 #include "chrome/common/content_settings.h"
 #include "content/public/common/common_param_traits.h"
 #include "content/public/common/page_type.h"
 #include "content/public/common/security_style.h"
 #include "content/public/common/webkit_param_traits.h"
 #include "googleurl/src/gurl.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_message_utils.h"
 #include "net/base/cert_status_flags.h"
 #include "net/base/host_port_pair.h"
@@ skipping 187 matching lines @@
   static void Log(const param_type& p, std::string* l);
 };
 
 }  // namespace IPC
 
 #endif  // CHROME_COMMON_AUTOMATION_MESSAGES_H_
 
 // Keep this internal message file unchanged to preserve line numbering
 // (and hence the dubious __LINE__-based message numberings) across versions.
 #include "chrome/common/automation_messages_internal.h"