Support using a Mojo message pipe in a ChannelHandle.

ipc/ipc_mojo_param_traits.h

 // Copyright 2015 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_MOJO_PARAM_TRAITS_H_
 #define IPC_IPC_MOJO_PARAM_TRAITS_H_
 
 #include <string>
 
 #include "ipc/ipc_export.h"
 #include "ipc/ipc_param_traits.h"
 #include "mojo/public/cpp/system/message_pipe.h"
 
 namespace base {
 class PickleIterator;
+class PickleSizer;
 }
 
 namespace IPC {
 
 class Message;
 
 template <>
 struct IPC_EXPORT ParamTraits<mojo::MessagePipeHandle> {
   typedef mojo::MessagePipeHandle param_type;
+  static void GetSize(base::PickleSizer* sizer, const param_type& p);
   static void Write(Message* m, const param_type& p);
   static bool Read(const Message* m, base::PickleIterator* iter, param_type* r);
   static void Log(const param_type& p, std::string* l);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_MOJO_PARAM_TRAITS_H_