Mojo: Move system embedder API files to mojo/system/embedder.

mojo/system/platform_handle.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_PLATFORM_HANDLE_H_
-#define MOJO_SYSTEM_PLATFORM_HANDLE_H_
-
-#include "build/build_config.h"
-#include "mojo/system/system_impl_export.h"
-
-#if defined(OS_WIN)
-#include <windows.h>
-#endif
-
-namespace mojo {
-namespace embedder {
-
-#if defined(OS_POSIX)
-struct MOJO_SYSTEM_IMPL_EXPORT PlatformHandle {
-  PlatformHandle() : fd(-1) {}
-  explicit PlatformHandle(int fd) : fd(fd) {}
-
-  void CloseIfNecessary();
-
-  bool is_valid() const { return fd != -1; }
-
-  int fd;
-};
-#elif defined(OS_WIN)
-struct MOJO_SYSTEM_IMPL_EXPORT PlatformHandle {
-  PlatformHandle() : handle(INVALID_HANDLE_VALUE) {}
-  explicit PlatformHandle(HANDLE handle) : handle(handle) {}
-
-  void CloseIfNecessary();
-
-  bool is_valid() const { return handle != INVALID_HANDLE_VALUE; }
-
-  HANDLE handle;
-};
-#else
-#error "Platform not yet supported."
-#endif
-
-}  // namespace embedder
-}  // namespace mojo
-
-#endif  // MOJO_SYSTEM_PLATFORM_HANDLE_H_