[web_dev_style] Changing :pseudo-element to ::pseudo-element to match

chrome/browser/resources/task_manager/task_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 {
   overflow: hidden;
 }
 
 /* Outer frame of the dialog. */
 body {
@@ skipping 50 matching lines @@
   -webkit-box-flex: 1;
 }
 
 /* Title Column text containers. */
 .detail-title {
   display: -webkit-box;
   height: 20px;
 }
 
 /* Bullets on the left of row. */
-.table-row > .table-row-cell:first-child:before {
+.table-row > .table-row-cell:first-child::before {
   -webkit-border-radius: 3px;
   background: #ccc;
   content: '';
   display: block;
   margin: 7px 4px 7px 7px;
   width: 6px;
 }
 
 .table-background-row {
   background-color: hsl(34, 91%, 87%);
@@ skipping 60 matching lines @@
 
 /* Container for the ok/cancel buttons. */
 .footer-right-container {
   -webkit-box-flex: 1;
   text-align: right;
 }
 
 button {
   margin: 2px 0 2px 8px;
 }