Convert WriteMessage...() to use the new user pointer handling (see r285350).

mojo/system/message_pipe.h

 // Copyright 2013 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 MOJO_SYSTEM_MESSAGE_PIPE_H_
 #define MOJO_SYSTEM_MESSAGE_PIPE_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 35 matching lines @@
   // Gets the type of the endpoint (used for assertions, etc.).
   MessagePipeEndpoint::Type GetType(unsigned port);
 
   // These are called by the dispatcher to implement its methods of
   // corresponding names. In all cases, the port |port| must be open.
   void CancelAllWaiters(unsigned port);
   void Close(unsigned port);
   // Unlike |MessagePipeDispatcher::WriteMessage()|, this does not validate its
   // arguments.
   MojoResult WriteMessage(unsigned port,
-                          const void* bytes,
+                          UserPointer<const void> bytes,
                           uint32_t num_bytes,
                           std::vector<DispatcherTransport>* transports,
                           MojoWriteMessageFlags flags);
   MojoResult ReadMessage(unsigned port,
                          UserPointer<void> bytes,
                          UserPointer<uint32_t> num_bytes,
                          DispatcherVector* dispatchers,
                          uint32_t* num_dispatchers,
                          MojoReadMessageFlags flags);
   MojoResult AddWaiter(unsigned port,
@@ skipping 45 matching lines @@
   base::Lock lock_;  // Protects the following members.
   scoped_ptr<MessagePipeEndpoint> endpoints_[2];
 
   DISALLOW_COPY_AND_ASSIGN(MessagePipe);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_MESSAGE_PIPE_H_