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

ui/webui/resources/css/overlay.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. */
 
 /* The shield that overlays the background. */
 .overlay {
   -webkit-box-align: center;
   -webkit-box-orient: vertical;
   -webkit-box-pack: center;
   /* TODO(dbeam): remove perspective when http://crbug.com/374970 is fixed. */
@@ skipping 81 matching lines @@
 .overlay .page > .close-button:hover {
   background-image: url(chrome://theme/IDR_CLOSE_DIALOG_H);
 }
 
 .overlay .page > .close-button:active {
   background-image: url(chrome://theme/IDR_CLOSE_DIALOG_P);
 }
 
 .overlay .page h1 {
   -webkit-padding-end: 24px;
-  -webkit-user-select: none;
   color: #333;
   /* 120% of the body's font-size of 84% is 16px. This will keep the relative
    * size between the body and these titles consistent. */
   font-size: 120%;
   /* TODO(flackr): Pages like sync-setup and delete user collapse the margin
    * above the top of the page. Use padding instead to make sure that the
    * headers of these pages have the correct spacing, but this should not be
    * necessary. See http://crbug.com/119029. */
   margin: 0;
   padding: 14px 17px 14px;
   text-shadow: white 0 1px 2px;
+  user-select: none;
 }
 
 .overlay .page .content-area {
   -webkit-box-flex: 1;
   overflow: auto;
   padding: 6px 17px 6px;
   position: relative;
 }
 
 .overlay .page .action-area {
@@ skipping 72 matching lines @@
 #overlay-container-1 {
   z-index: 11;
 }
 #overlay-container-2 {
   z-index: 12;
 }
 
 .transparent {
   opacity: 0;
 }