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

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

 // Copyright (c) 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_NODE_H_
 #define LIBRARIES_NACL_IO_GOOGLEDRIVEFS_NODE_H_
 
 #include <sys/stat.h>
 
 #include "nacl_io/googledrivefs/googledrivefs.h"
 #include "nacl_io/kernel_handle.h"
 #include "nacl_io/node.h"
 #include "nacl_io/osdirent.h"
 
 namespace nacl_io {
 
+// This is not further implemented.
+// PNaCl is on a path to deprecation, and WebAssembly is
+// the focused technology.
+
 class GoogleDriveFsNode : public Node {
  public:
   GoogleDriveFsNode(GoogleDriveFs* googledrivefs);
 
   Error GetDents(size_t offs, struct dirent* pdir, size_t size, int* out_bytes);
   Error Write(const HandleAttr& attr,
               const void* buf,
               size_t count,
               int* out_bytes);
   Error FTruncate(off_t length);
   Error Read(const HandleAttr& attr, void* buf, size_t count, int* out_bytes);
   Error GetSize(off_t* out_size);
   Error GetStat(struct stat* pstat);
   Error Init(int open_flags);
 };
 
 }  // namespace nacl_io
 
 #endif  // LIBRARIES_NACL_IO_GOOGLEDRIVEFS_NODE_H_