Files.app: Keep the background color of top buttons as pressed until it is released.

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 {
   height: 100%;
 }
 
 html.col-resize * {
   cursor: col-resize !important;
@@ skipping 751 matching lines @@
   min-width: 0;
   outline: none;
   padding: 0;
   width: 32px;
 }
 
 body[new-ui] .dialog-header .buttonbar button:not(:active) {
   -webkit-box-shadow: none;
 }
 
-body[new-ui] .dialog-header button:not(:hover):not(focus) {
+body[new-ui] .dialog-header button:not(:hover):not(focus):not(:active) {
   background-color: transparent;
   border-color: transparent;
 }
 
 #search-box,
 #filename-input-box input {
   border: 1px solid #d9d9d9;
   border-radius: 1px;
   border-top: 1px solid #c0c0c0;
   box-sizing: border-box;
@@ skipping 1573 matching lines @@
 body[new-ui] #iframe-drag-area {
   -webkit-app-region: drag;
   height: 45px;
   left: 64px;
   position: absolute;
   right: 70px;
   top: 0;
   width: auto;
   z-index: 101;
 }