Drop the -webkit prefix from user-select CSS rule in ui/.

ui/file_manager/video_player/css/video_player.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. */
 
 body {
-  -webkit-user-select: none;
   background: black;
   font-size: 84%;
   margin: 0;
   overflow: hidden;
+  user-select: none;
 }
 
 #video-player {
   height: 100%;
   left: 0;
   position: absolute;
   top: 0;
   width: 100%;
 }
 
@@ skipping 144 matching lines @@
   color: white;
   display: -webkit-box;
   height: 54px;
   padding-left: 70px;
   padding-right: 35px;
 }
 
 #error:not([visible]) {
   display: none;
 }