[NaCl SDK] Add comments in the implementation code of GoogleDriveFs

native_client_sdk/src/libraries/nacl_io/googledrivefs/googledrivefs.h

 // Copyright 2016 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 LIBRARIES_NACL_IO_GOOGLEDRIVEFS_H_
 #define LIBRARIES_NACL_IO_GOOGLEDRIVEFS_H_
 
 #include "nacl_io/filesystem.h"
 #include "nacl_io/node.h"
 #include "nacl_io/path.h"
 #include "nacl_io/typed_fs_factory.h"
 
 namespace nacl_io {
 
+// This is not further implemented.
+// PNaCl is on a path to deprecation, and WebAssembly is
+// the focused technology.
+
 class GoogleDriveFs : public Filesystem {
  protected:
   GoogleDriveFs();
 
   Error Init(const FsInitArgs& args);
 
  public:
   Error OpenWithMode(const Path& path,
                      int open_flags,
                      mode_t mode,
                      ScopedNode* out_node);
   Error Unlink(const Path& path);
   Error Mkdir(const Path& path, int permissions);
   Error Rmdir(const Path& path);
   Error Remove(const Path& path);
   Error Rename(const Path& path, const Path& newPath);
 
  private:
   friend class TypedFsFactory<GoogleDriveFs>;
 };
 
 }  // namespace nacl_io
 
 #endif  // LIBRARIES_NACL_IO_GOOGLEDRIVEFS_H_