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

mojo/system/core_unittest.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/core.h"
 
 #include <limits>
 
 #include "base/basictypes.h"
 #include "base/threading/platform_thread.h"
@@ skipping 23 matching lines @@
   EXPECT_EQ(0u, info.GetCtorCallCount());
   MojoHandle h = CreateMockHandle(&info);
   EXPECT_EQ(1u, info.GetCtorCallCount());
   EXPECT_NE(h, MOJO_HANDLE_INVALID);
 
   EXPECT_EQ(0u, info.GetWriteMessageCallCount());
   EXPECT_EQ(MOJO_RESULT_OK,
             core()->WriteMessage(h, NullUserPointer(), 0, NullUserPointer(), 0,
                                  MOJO_WRITE_MESSAGE_FLAG_NONE));
   EXPECT_EQ(1u, info.GetWriteMessageCallCount());
-  EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
-            core()->WriteMessage(h, NullUserPointer(), 1, NullUserPointer(), 0,
-                                 MOJO_WRITE_MESSAGE_FLAG_NONE));
-  EXPECT_EQ(2u, info.GetWriteMessageCallCount());
 
   EXPECT_EQ(0u, info.GetReadMessageCallCount());
   uint32_t num_bytes = 0;
   EXPECT_EQ(MOJO_RESULT_OK,
             core()->ReadMessage(h, NullUserPointer(),
                                 MakeUserPointer(&num_bytes), NullUserPointer(),
                                 NullUserPointer(),
                                 MOJO_READ_MESSAGE_FLAG_NONE));
   EXPECT_EQ(1u, info.GetReadMessageCallCount());
   EXPECT_EQ(MOJO_RESULT_OK,
@@ skipping 935 matching lines @@
   EXPECT_EQ(MOJO_RESULT_OK, core()->Close(h_passing[1]));
   EXPECT_EQ(MOJO_RESULT_OK, core()->Close(ph));
   EXPECT_EQ(MOJO_RESULT_OK, core()->Close(ch));
 }
 
 // TODO(vtl): Test |DuplicateBufferHandle()| and |MapBuffer()|.
 
 }  // namespace
 }  // namespace system
 }  // namespace mojo