Moves some files into mojo/common

mojo/shell/scoped_message_pipe.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/shell/scoped_message_pipe.h"
-
-namespace mojo {
-namespace shell {
-
-ScopedMessagePipe::ScopedMessagePipe()
-    : handle_0_(MOJO_HANDLE_INVALID),
-      handle_1_(MOJO_HANDLE_INVALID) {
-  MojoCreateMessagePipe(&handle_0_, &handle_1_);
-}
-
-ScopedMessagePipe::~ScopedMessagePipe() {
-  if (handle_0_ != MOJO_HANDLE_INVALID)
-    MojoClose(handle_0_);
-
-  if (handle_1_ != MOJO_HANDLE_INVALID)
-    MojoClose(handle_1_);
-}
-
-}  // namespace shell
-}  // namespace mojo