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

mojo/system/local_data_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_LOCAL_DATA_PIPE_H_
 #define MOJO_SYSTEM_LOCAL_DATA_PIPE_H_
 
 #include "base/basictypes.h"
 #include "base/memory/aligned_memory.h"
 #include "base/memory/ref_counted.h"
@@ skipping 17 matching lines @@
  private:
   friend class base::RefCountedThreadSafe<LocalDataPipe>;
   virtual ~LocalDataPipe();
 
   // |DataPipe| implementation:
   virtual void ProducerCloseImplNoLock() OVERRIDE;
   virtual MojoResult ProducerWriteDataImplNoLock(const void* elements,
                                                  uint32_t* num_bytes,
                                                  bool all_or_none) OVERRIDE;
   virtual MojoResult ProducerBeginWriteDataImplNoLock(
-      void** buffer,
-      uint32_t* buffer_num_bytes,
-      bool all_or_none) OVERRIDE;
+      UserPointer<void*> buffer,
+      UserPointer<uint32_t> buffer_num_bytes,
+      uint32_t min_num_bytes_to_write) OVERRIDE;
   virtual MojoResult ProducerEndWriteDataImplNoLock(
       uint32_t num_bytes_written) OVERRIDE;
   virtual HandleSignalsState
       ProducerGetHandleSignalsStateNoLock() const OVERRIDE;
   virtual void ConsumerCloseImplNoLock() OVERRIDE;
   virtual MojoResult ConsumerReadDataImplNoLock(void* elements,
                                                 uint32_t* num_bytes,
                                                 bool all_or_none) OVERRIDE;
   virtual MojoResult ConsumerDiscardDataImplNoLock(uint32_t* num_bytes,
                                                    bool all_or_none) OVERRIDE;
@@ skipping 24 matching lines @@
   size_t start_index_;
   size_t current_num_bytes_;
 
   DISALLOW_COPY_AND_ASSIGN(LocalDataPipe);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_LOCAL_DATA_PIPE_H_