Generate param traits even when shared by mutliple message files.

content/public/common/common_param_traits.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.
 
 // This file is used to define IPC::ParamTraits<> specializations for a number
 // of types so that they can be serialized over IPC.  IPC::ParamTraits<>
 // specializations for basic types (like int and std::string) and types in the
 // 'base' project can be found in ipc/ipc_message_utils.h.  This file contains
 // specializations for types that are used by the content code, and which need
 // manual serialization code.  This is usually because they're not structs with
 // public members, or because the same type is being used in multiple
 // *_messages.h headers.
 
 #ifndef CONTENT_PUBLIC_COMMON_COMMON_PARAM_TRAITS_H_
 #define CONTENT_PUBLIC_COMMON_COMMON_PARAM_TRAITS_H_
 #pragma once
 
 #include "base/memory/ref_counted.h"
 #include "content/common/content_export.h"
-#include "content/public/common/console_message_level.h"
 #include "content/public/common/page_transition_types.h"
 #include "content/public/common/security_style.h"
 #include "googleurl/src/gurl.h"
 #include "ipc/ipc_message_utils.h"
 #include "net/base/ip_endpoint.h"
 #include "net/url_request/url_request_status.h"
 #include "third_party/WebKit/Source/Platform/chromium/public/WebReferrerPolicy.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/surface/transport_dib.h"
 #include "webkit/glue/resource_type.h"
 
+// Explicitly guarded include of _defs.h files in header files.

[jam, 2012/06/20 21:55:48]

even though I see why, it's odd reading that ifdef in  traits/message files.

how many traits does this cover? i guess you'd want to get rid of
common_param_traits in content/chrome completely?

+#ifndef CONTENT_PUBLIC_COMMON_COMMON_PARAM_TRAITS_DEFS_H_
+#include "content/public/common/common_param_traits_defs.h"
+#endif
+
 class SkBitmap;
 
 namespace content {
 struct Referrer;
 }
 
 namespace gfx {
 class Point;
 class Rect;
 class Size;
@@ skipping 199 matching lines @@
 template <>
 struct SimilarTypeTraits<content::PageTransition> {
   typedef int Type;
 };
 
 template <>
 struct SimilarTypeTraits<content::SecurityStyle> {
   typedef int Type;
 };
 
-template<>
-struct CONTENT_EXPORT ParamTraits<content::ConsoleMessageLevel> {
-  typedef content::ConsoleMessageLevel param_type;
-  static void Write(Message* m, const param_type& p);
-  static bool Read(const Message* m, PickleIterator* iter, param_type* r);
-  static void Log(const param_type& p, std::string* l);
-};
-
 }  // namespace IPC
 
 #endif  // CONTENT_PUBLIC_COMMON_COMMON_PARAM_TRAITS_H_