Convert base::ScopedFD to (mojo::embedder::)ScopedPlatformHandle.

mojo/edk/embedder/scoped_platform_handle.h

 // Copyright 2014 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_EDK_EMBEDDER_SCOPED_PLATFORM_HANDLE_H_
 #define MOJO_EDK_EMBEDDER_SCOPED_PLATFORM_HANDLE_H_
 
 #include "base/move.h"
 #include "mojo/edk/embedder/platform_handle.h"
 #include "mojo/edk/system/system_impl_export.h"
 #include "mojo/public/c/system/macros.h"
 
 namespace mojo {
 namespace embedder {
 
+// Scoper for |PlatformHandle|s, which are file descriptors on POSIX and
+// |HANDLE|s on Windows.
 class MOJO_SYSTEM_IMPL_EXPORT ScopedPlatformHandle {
   MOVE_ONLY_TYPE_WITH_MOVE_CONSTRUCTOR_FOR_CPP_03(ScopedPlatformHandle)
 
  public:
   ScopedPlatformHandle() {}
   explicit ScopedPlatformHandle(PlatformHandle handle) : handle_(handle) {}
   ~ScopedPlatformHandle() { handle_.CloseIfNecessary(); }
 
   // Move-only constructor and operator=.
   ScopedPlatformHandle(ScopedPlatformHandle&& other)
@@ skipping 27 matching lines @@
   bool is_valid() const { return handle_.is_valid(); }
 
  private:
   PlatformHandle handle_;
 };
 
 }  // namespace embedder
 }  // namespace mojo
 
 #endif  // MOJO_EDK_EMBEDDER_SCOPED_PLATFORM_HANDLE_H_