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

mojo/system/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_DISPATCHER_H_
 #define MOJO_SYSTEM_DISPATCHER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 84 matching lines @@
   MojoResult WriteData(const void* elements,
                        uint32_t* elements_num_bytes,
                        MojoWriteDataFlags flags);
   MojoResult BeginWriteData(UserPointer<void*> buffer,
                             UserPointer<uint32_t> buffer_num_bytes,
                             MojoWriteDataFlags flags);
   MojoResult EndWriteData(uint32_t num_bytes_written);
   MojoResult ReadData(void* elements,
                       uint32_t* num_bytes,
                       MojoReadDataFlags flags);
-  MojoResult BeginReadData(const void** buffer,
-                           uint32_t* buffer_num_bytes,
+  MojoResult BeginReadData(UserPointer<const void*> buffer,
+                           UserPointer<uint32_t> buffer_num_bytes,
                            MojoReadDataFlags flags);
   MojoResult EndReadData(uint32_t num_bytes_read);
   // |options| may be null. |new_dispatcher| must not be null, but
   // |*new_dispatcher| should be null (and will contain the dispatcher for the
   // new handle on success).
   MojoResult DuplicateBufferHandle(
       const MojoDuplicateBufferHandleOptions* options,
       scoped_refptr<Dispatcher>* new_dispatcher);
   MojoResult MapBuffer(uint64_t offset,
                        uint64_t num_bytes,
@@ skipping 109 matching lines @@
                                          uint32_t* num_bytes,
                                          MojoWriteDataFlags flags);
   virtual MojoResult BeginWriteDataImplNoLock(
       UserPointer<void*> buffer,
       UserPointer<uint32_t> buffer_num_bytes,
       MojoWriteDataFlags flags);
   virtual MojoResult EndWriteDataImplNoLock(uint32_t num_bytes_written);
   virtual MojoResult ReadDataImplNoLock(void* elements,
                                         uint32_t* num_bytes,
                                         MojoReadDataFlags flags);
-  virtual MojoResult BeginReadDataImplNoLock(const void** buffer,
-                                             uint32_t* buffer_num_bytes,
-                                             MojoReadDataFlags flags);
+  virtual MojoResult BeginReadDataImplNoLock(
+      UserPointer<const void*> buffer,
+      UserPointer<uint32_t> buffer_num_bytes,
+      MojoReadDataFlags flags);
   virtual MojoResult EndReadDataImplNoLock(uint32_t num_bytes_read);
   virtual MojoResult DuplicateBufferHandleImplNoLock(
       const MojoDuplicateBufferHandleOptions* options,
       scoped_refptr<Dispatcher>* new_dispatcher);
   virtual MojoResult MapBufferImplNoLock(
       uint64_t offset,
       uint64_t num_bytes,
       MojoMapBufferFlags flags,
       scoped_ptr<RawSharedBufferMapping>* mapping);
   virtual MojoResult AddWaiterImplNoLock(Waiter* waiter,
@@ skipping 123 matching lines @@
 
   Dispatcher* dispatcher_;
 
   // Copy and assign allowed.
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_DISPATCHER_H_