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

mojo/system/message_pipe_dispatcher.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_DISPATCHER_H_
 #define MOJO_SYSTEM_MESSAGE_PIPE_DISPATCHER_H_
 
 #include <utility>
 
 #include "base/basictypes.h"
@@ skipping 65 matching lines @@
   // |Dispatcher| protected methods:
   virtual void CancelAllWaitersNoLock() OVERRIDE;
   virtual void CloseImplNoLock() OVERRIDE;
   virtual scoped_refptr<Dispatcher>
       CreateEquivalentDispatcherAndCloseImplNoLock() OVERRIDE;
   virtual MojoResult WriteMessageImplNoLock(
       const void* bytes,
       uint32_t num_bytes,
       std::vector<DispatcherTransport>* transports,
       MojoWriteMessageFlags flags) OVERRIDE;
-  virtual MojoResult ReadMessageImplNoLock(void* bytes,
-                                           uint32_t* num_bytes,
+  virtual MojoResult ReadMessageImplNoLock(UserPointer<void> bytes,
+                                           UserPointer<uint32_t> num_bytes,
                                            DispatcherVector* dispatchers,
                                            uint32_t* num_dispatchers,
                                            MojoReadMessageFlags flags) OVERRIDE;
   virtual MojoResult AddWaiterImplNoLock(Waiter* waiter,
                                          MojoHandleSignals signals,
                                          uint32_t context) OVERRIDE;
   virtual void RemoveWaiterImplNoLock(Waiter* waiter) OVERRIDE;
   virtual void StartSerializeImplNoLock(Channel* channel,
                                         size_t* max_size,
                                         size_t* max_platform_handles) OVERRIDE;
@@ skipping 24 matching lines @@
     return static_cast<MessagePipeDispatcher*>(dispatcher());
   }
 
   // Copy and assign allowed.
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_MESSAGE_PIPE_DISPATCHER_H_