drive: Use "/drive/root" namespace and fix Files app and tests.

chrome/browser/resources/file_manager/js/directory_model.js

 // Copyright (c) 2012 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';
 
 // If directory files changes too often, don't rescan directory more than once
 // per specified interval
 var SIMULTANEOUS_RESCAN_INTERVAL = 1000;
 // Used for operations that require almost instant rescan.
@@ skipping 38 matching lines @@
 }
 
 /**
  * Fake entry to be used in currentDirEntry_ when current directory is
  * unmounted DRIVE. TODO(haruki): Support "drive/root" and "drive/other".
  * @type {Object}
  * @const
  * @private
  */
 DirectoryModel.fakeDriveEntry_ = {
-  fullPath: RootDirectory.DRIVE,
+  fullPath: RootDirectory.DRIVE + '/' + DriveSubRootDirectory.ROOT,
   isDirectory: true
 };
 
 /**
  * Fake entry representing a psuedo directory, which contains Drive files
  * available offline. This entry works as a trigger to start a search using
  * DirectoryContentsDriveOffline. specialSearch() must be called to start a
  * special search.
  * @type {Object}
  * @const
@@ skipping 1368 matching lines @@
         }.bind(this));
   }
 };
 
 /**
  * @return {DirectoryEntry} Current watched directory entry.
  */
 FileWatcher.prototype.getWatchedDirectoryEntry = function() {
   return this.watchedDirectoryEntry_;
 };