Drive: Add "Clear Local Cache" in the Gear menu to clear all local cache of Drive.

chrome/browser/resources/file_manager/css/file_manager.css

 /* 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. */
 
 html.col-resize * {
   cursor: col-resize !important;
 }
 
 /* Outer frame of the dialog. */
 body {
@@ skipping 1288 matching lines @@
 
 body[ash] .dialog-title,
 body[type='full-page'] [invisibleif='full-page'],
 body:not([type='full-page']) [visibleif='full-page'],
 body:not([type='saveas-file']) [visibleif='saveas-file'],
 body:not([type='saveas-file']):not([type='full-page'])
     [visibleif='saveas-file full-page'] {
   display: none;
 }
 
+body:not([ctrl-pressing]) [visibleif='ctrl'] {
+  display: none;
+}
+
 #gdata-settings {
   background-image: url('../images/files/ui/settings.svg');
   background-position: 20px center;
   background-repeat: no-repeat;
   overflow: hidden;
   text-align: left;
   width: 54px;
 }
 
 #gdata-settings span.disclosureindicator {
@@ skipping 145 matching lines @@
   height: 100%;
 }
 
 #list-container .table-header-cell:hover {
   background-color: #f2f2f2;
 }
 
 button:focus {
   outline-color: rgb(77, 144, 254);
 }