mandoline filesystem: add a sqlite3 vfs to proxy filesystem usage.

components/filesystem/public/interfaces/directory.mojom

 // Copyright 2015 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.
 
 module filesystem;
 
 import "components/filesystem/public/interfaces/file.mojom";
 import "components/filesystem/public/interfaces/types.mojom";
 
 // This interface provides access to a directory in a "file system", providing
@@ skipping 24 matching lines @@
                 Directory&? directory,
                 uint32 open_flags) => (FileError error);
 
   // Renames/moves the file/directory given by |path| to |new_path|.
   Rename(string path, string new_path) => (FileError error);
 
   // Deletes the given path, which may be a file or a directory (see
   // |kDeleteFlag...| for details).
   Delete(string path, uint32 delete_flags) => (FileError error);
 
+  // Returns true if |path| exists.
+  Exists(string path) => (FileError error, bool exists);
+
+  // Returns true if |path| is writable.
+  IsWritable(string path) => (FileError error, bool is_writable);
+
+  // Opens a file descriptor on this directory and calls
+  // fsync()/FlushFileBuffers().
+  Flush() => (FileError error);
+
   // TODO(vtl): directory "streaming"?
   // TODO(vtl): "make root" (i.e., prevent cd-ing, etc., to parent); note that
   // this would require a much more complicated implementation (e.g., it needs
   // to be "inherited" by OpenDirectory(), and the enforcement needs to be valid
   // even if the opened directory is subsequently moved -- e.g., closer to the
   // "root")
   // TODO(vtl): Add a "watch"?
 };