Plumbing though mode parameter to open, since fusefs can make use of it.

native_client_sdk/src/libraries/nacl_io/memfs/mem_fs.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 LIBRARIES_NACL_IO_MEMFS_MEM_FS_H_
 #define LIBRARIES_NACL_IO_MEMFS_MEM_FS_H_
 
 #include "nacl_io/filesystem.h"
 #include "nacl_io/typed_fs_factory.h"
 
@@ skipping 11 matching lines @@
   // required to use correct locking as needed.
 
   // Allocate or free an INODE number.
   int AllocateINO();
   void FreeINO(int ino);
 
   // Find a Node specified node optionally failing if type does not match.
   virtual Error FindNode(const Path& path, int type, ScopedNode* out_node);
 
  public:
-  virtual Error Open(const Path& path, int mode, ScopedNode* out_node);
+  virtual Error OpenWithMode(const Path& path, int open_flags, mode_t mode,
+                             ScopedNode* out_node);
   virtual Error Unlink(const Path& path);
   virtual Error Mkdir(const Path& path, int perm);
   virtual Error Rmdir(const Path& path);
   virtual Error Remove(const Path& path);
   virtual Error Rename(const Path& path, const Path& newpath);
 
  private:
   static const int REMOVE_DIR = 1;
   static const int REMOVE_FILE = 2;
   static const int REMOVE_ALL = REMOVE_DIR | REMOVE_FILE;
 
   Error RemoveInternal(const Path& path, int remove_type);
 
   ScopedNode root_;
 
   friend class TypedFsFactory<MemFs>;
   DISALLOW_COPY_AND_ASSIGN(MemFs);
 };
 
 }  // namespace nacl_io
 
 #endif  // LIBRARIES_NACL_IO_MEMFS_MEM_FS_H_