Eliminate usage of InterfacePtr::WaitForIncomingResponse.

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.mojom;
 
 import "components/filesystem/public/interfaces/file.mojom";
 import "components/filesystem/public/interfaces/types.mojom";
 
 struct FileOpenDetails {
@@ skipping 73 matching lines @@
 
   // Gets information about this file. On success, |file_information| is
   // non-null and will contain this information.
   [Sync]
   StatFile(string path) => (FileError error, FileInformation? file_information);
 
   // Creates a copy of this directory.
   Clone(Directory& directory);
 
   // Reads the contents of an entire file.
+  [Sync]
   ReadEntireFile(string path) => (FileError error, array<uint8> data);
 
   // Writes |data| to |path|, overwriting the file if it already exists.
+  [Sync]
   WriteFile(string path, array<uint8> data) => (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"?
 };