Remove root resource id aliasing from DriveResourceMetadata.

chrome/browser/resources/file_manager/js/volume_manager.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';
 
 /**
  * VolumeManager is responsible for tracking list of mounted volumes.
  *
  * @constructor
@@ skipping 295 matching lines @@
  *
  * @param {string} mountPath Drive mount path.
  * @param {function(boolean, FileError=)} callback To be called when waiting
  *     finishes. If the case of error, there may be a FileError parameter.
  * @private
  */
 VolumeManager.prototype.waitDriveLoaded_ = function(mountPath, callback) {
   chrome.fileBrowserPrivate.requestLocalFileSystem(function(filesystem) {
     filesystem.root.getDirectory(mountPath, {},
         function(entry) {
-            // After introducion of the 'fast-fetch' feature, getting the root
-            // entry does not start fetching data. Rather, it starts when the
-            // entry is read.
-            entry.createReader().readEntries(
-                callback.bind(null, true),
-                callback.bind(null, false));
+          // After file system is mounted, we need to "read" drive grand root
+          // entry at first. It loads mydrive root entry as a part of
+          // 'fast-fetch' quickly, and starts full feed fetch in parallel.
+          // Without this read, accessing mydrive root will be 'full-fetch'
+          // rather than 'fast-fetch' on the current architecture.
+          // Just "getting" the grand root entry doesn't trigger it. Rather,
+          // it starts when the entry is "read".
+          entry.createReader().readEntries(
+              callback.bind(null, true),
+              callback.bind(null, false));
         },
         callback.bind(null, false));
   });
 };
 
 /**
  * @param {string} mountPath Path to the volume.
  * @param {VolumeManager?} error Mounting error if any.
  * @param {function(Object)} callback Result acceptor.
  * @private
@@ skipping 251 matching lines @@
 
 /**
  * @param {string} mountPath Mount path.
  * @private
  */
 VolumeManager.prototype.validateMountPath_ = function(mountPath) {
   if (!/^\/(drive|drive_offline|Downloads)$/.test(mountPath) &&
       !/^\/((archive|removable|drive)\/[^\/]+)$/.test(mountPath))
     throw new Error('Invalid mount path: ', mountPath);
 };