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

chrome/browser/resources/shared/css/menu.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. */
 
 menu {
   -webkit-box-shadow: 0 2px 4px rgba(0, 0, 0, .50);
   background: white;
   color: black;
   cursor: default;
   left: 0;
@@ skipping 47 matching lines @@
 
 menu > :not(hr)[selected] {
   background-color: rgb(220, 229, 250);
 }
 
 menu > :not(hr)[selected]:active {
   background-color: rgb(66, 109, 201);
   color: #fff;
 }
 
-menu > [checked]:before {
+menu > [checked]::before {
   content: url('../images/checkbox_black.png');
   display: inline-block;
   height: 9px;
   margin: 0 5px;
   vertical-align: 50%;
   width: 9px;
 }
 
 menu > [checked] {
   -webkit-padding-start: 0;
 }
 
-menu > [selected][checked]:active:before {
+menu > [selected][checked]:active::before {
   content: url('../images/checkbox_white.png');
 }
 
-/* TODO(zvorygin) menu > [shortcutText]:after - this selector is much better,
- * but it's buggy in current webkit revision, so I have to use [showShortcuts]
+/* TODO(zvorygin) menu > [shortcutText]::after - this selector is much better,
+ * but it's buggy in current webkit revision, so I have to use [showShortcuts].
  */
-menu[showShortcuts] > :after {
+menu[showShortcuts] > ::after {
   -webkit-padding-start: 30px;
   color: #999;
   content: attr(shortcutText);
   float: right;
 }