[File Manager] Hide hover state when using keyboard.

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. */
 
 /* Outer frame of the dialog. */
 body {
    -webkit-box-flex: 1;
    -webkit-box-orient: vertical;
    -webkit-transition: opacity 70ms linear;
    -webkit-user-select: none;
@@ skipping 629 matching lines @@
   background-color: rgb(193, 211, 236);
 }
 
 .list-container list > .accepts,
 .list-container list > :hover,
 .list-container grid > :hover {
   background-color: rgb(242, 246, 250);
   border-color: rgb(242, 246, 250);
 }
 
+.list-container.nohover list > :not([selected]):hover,
+.list-container.nohover grid > :not([selected]):hover {
+  background-color: transparent;
+  border-color: transparent;
+}
+
 .table-row-cell .filename-label,
 .thumbnail-item .filename-label,
 /* Show ellipsis in cells. The name column has different structure and overrides
    this rule. */
 .table-row-cell > div {
   display: block;
   overflow: hidden;
   text-overflow: ellipsis;
   white-space: nowrap;
 }
@@ skipping 580 matching lines @@
   top: 0;
   width: 40px;
 }
 
 .unmounted-panel:not([loading]) > .gdata.loading,
 .unmounted-panel:not([error]) > .gdata.error,
 .unmounted-panel:not([retry]) > .gdata.retry,
 .unmounted-panel:not([retry]) > .gdata.learn-more {
   display: none;
 }