[fsp] Add support for creating directories.

chrome/test/data/extensions/api_test/file_system_provider/evil/test.js

 // Copyright 2014 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.
 
 'use strict';
 
 /**
- * @type {DOMFileSystem}
- */
-var fileSystem = null;
-
-/**
  * Map of opened files, from a <code>openRequestId</code> to <code>filePath
  * </code>.
  * @type {Object.<number, string>}
  */
 var openedFiles = {};
 
 /**
  * Metadata for a testing file.
  * @type {Object}
  * @const
@@ skipping 277 matching lines @@
             chrome.test.fail('Opening a file should fail.');
           },
           function(error) {
             onTestSuccess();
           });
     },  ]);
 }
 
 // Setup and run all of the test cases.
 setUp(runTests);