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

mojo/system/message_in_transit.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_IN_TRANSIT_H_
 #define MOJO_SYSTEM_MESSAGE_IN_TRANSIT_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/aligned_memory.h"
 #include "base/memory/scoped_ptr.h"
 #include "mojo/system/dispatcher.h"
+#include "mojo/system/memory.h"
 #include "mojo/system/system_impl_export.h"
 
 namespace mojo {
 namespace system {
 
 class Channel;
 class TransportData;
 
 // This class is used to represent data in transit. It is thread-unsafe.
 //
@@ skipping 100 matching lines @@
     // own its data. (If you're copying/assigning this, you're probably doing
     // something wrong.)
     DISALLOW_COPY_AND_ASSIGN(View);
   };
 
   // |bytes| is optional; if null, the message data will be zero-initialized.
   MessageInTransit(Type type,
                    Subtype subtype,
                    uint32_t num_bytes,
                    const void* bytes);
+  // |bytes| should be valid (and non-null), unless |num_bytes| is zero.
+  MessageInTransit(Type type,
+                   Subtype subtype,
+                   uint32_t num_bytes,
+                   UserPointer<const void> bytes);
   // Constructs a |MessageInTransit| from a |View|.
   explicit MessageInTransit(const View& message_view);
 
   ~MessageInTransit();
 
   // Gets the size of the next message from |buffer|, which has |buffer_size|
   // bytes currently available, returning true and setting |*next_message_size|
   // on success. |buffer| should be aligned on a |kMessageAlignment| boundary
   // (and on success, |*next_message_size| will be a multiple of
   // |kMessageAlignment|).
@@ skipping 82 matching lines @@
     // Size of actual message data.
     uint32_t num_bytes;
     uint32_t unused;
   };
 
   const Header* header() const {
     return reinterpret_cast<const Header*>(main_buffer_.get());
   }
   Header* header() { return reinterpret_cast<Header*>(main_buffer_.get()); }
 
+  void ConstructorHelper(Type type,
+                         Subtype subtype,
+                         uint32_t num_bytes);
   void UpdateTotalSize();
 
   const size_t main_buffer_size_;
   const scoped_ptr<char, base::AlignedFreeDeleter> main_buffer_;  // Never null.
 
   scoped_ptr<TransportData> transport_data_;  // May be null.
 
   // Any dispatchers that may be attached to this message. These dispatchers
   // should be "owned" by this message, i.e., have a ref count of exactly 1. (We
   // allow a dispatcher entry to be null, in case it couldn't be duplicated for
   // some reason.)
   scoped_ptr<DispatcherVector> dispatchers_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageInTransit);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_MESSAGE_IN_TRANSIT_H_