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

mojo/system/dispatcher.cc

 // 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.
 
 #include "mojo/system/dispatcher.h"
 
 #include "base/logging.h"
 #include "mojo/system/constants.h"
 #include "mojo/system/message_pipe_dispatcher.h"
 #include "mojo/system/platform_handle_dispatcher.h"
@@ skipping 156 matching lines @@
 MojoResult Dispatcher::ReadData(void* elements,
                                 uint32_t* num_bytes,
                                 MojoReadDataFlags flags) {
   base::AutoLock locker(lock_);
   if (is_closed_)
     return MOJO_RESULT_INVALID_ARGUMENT;
 
   return ReadDataImplNoLock(elements, num_bytes, flags);
 }
 
-MojoResult Dispatcher::BeginReadData(const void** buffer,
-                                     uint32_t* buffer_num_bytes,
+MojoResult Dispatcher::BeginReadData(UserPointer<const void*> buffer,
+                                     UserPointer<uint32_t> buffer_num_bytes,
                                      MojoReadDataFlags flags) {
   base::AutoLock locker(lock_);
   if (is_closed_)
     return MOJO_RESULT_INVALID_ARGUMENT;
 
   return BeginReadDataImplNoLock(buffer, buffer_num_bytes, flags);
 }
 
 MojoResult Dispatcher::EndReadData(uint32_t num_bytes_read) {
   base::AutoLock locker(lock_);
@@ skipping 115 matching lines @@
 
 MojoResult Dispatcher::ReadDataImplNoLock(void* /*elements*/,
                                           uint32_t* /*num_bytes*/,
                                           MojoReadDataFlags /*flags*/) {
   lock_.AssertAcquired();
   DCHECK(!is_closed_);
   // By default, not supported. Only needed for data pipe dispatchers.
   return MOJO_RESULT_INVALID_ARGUMENT;
 }
 
-MojoResult Dispatcher::BeginReadDataImplNoLock(const void** /*buffer*/,
-                                               uint32_t* /*buffer_num_bytes*/,
-                                               MojoReadDataFlags /*flags*/) {
+MojoResult Dispatcher::BeginReadDataImplNoLock(
+    UserPointer<const void*> /*buffer*/,
+    UserPointer<uint32_t> /*buffer_num_bytes*/,
+    MojoReadDataFlags /*flags*/) {
   lock_.AssertAcquired();
   DCHECK(!is_closed_);
   // By default, not supported. Only needed for data pipe dispatchers.
   return MOJO_RESULT_INVALID_ARGUMENT;
 }
 
 MojoResult Dispatcher::EndReadDataImplNoLock(uint32_t /*num_bytes_read*/) {
   lock_.AssertAcquired();
   DCHECK(!is_closed_);
   // By default, not supported. Only needed for data pipe dispatchers.
@@ skipping 126 matching lines @@
 // DispatcherTransport ---------------------------------------------------------
 
 void DispatcherTransport::End() {
   DCHECK(dispatcher_);
   dispatcher_->lock_.Release();
   dispatcher_ = NULL;
 }
 
 }  // namespace system
 }  // namespace mojo