EDK: Move {platform_handle,scoped_platform_handle}.* to //mojo/edk/platform.

mojo/edk/embedder/platform_handle.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/edk/embedder/platform_handle.h"
-
-#include <unistd.h>
-
-#include "base/logging.h"
-
-namespace mojo {
-namespace embedder {
-
-void PlatformHandle::CloseIfNecessary() {
-  if (!is_valid())
-    return;
-
-  bool success = (close(fd) == 0);
-  DPCHECK(success);
-  fd = -1;
-}
-
-}  // namespace embedder
-}  // namespace mojo