Issue 2408 - Improved accessibility of checkboxes in options page

skin/options.css

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2015 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 401 matching lines @@
   border-radius: 5px;
   padding: 0px 40px;
 }
 
 .table::-webkit-scrollbar-thumb:hover,
 #custom-wrapper::-webkit-scrollbar-thumb:hover
 {
   background-color: #A1A1A1;
 }
 
+.table input[type="checkbox"]
+{
+  margin-top: 0px;
+  -moz-margin-end: 20px;
+  -webkit-margin-end: 20px;
+  padding: 0px 0px 0px 0px;
+  visibility: hidden;
+}
+
+.table input[type="checkbox"]::before
+{
+  content: "";
+  background-position: -51px 0px;
+  height: 18px;
+  width: 18px;
+  visibility: visible;
+}
+
+.table input[type="checkbox"]:checked::before
+{
+  content: "";
+  background-position: -68px 0px;
+  height: 18px;
+  padding: 0px;
+  width: 18px;
+  visibility: visible;
+}
+
 .table button.delete
 {
   background-color: transparent;
   background-position: -9px -32px;
   border: 0px;
   height: 10px;
   margin-top: 5px;
   -moz-margin-end: 20px;
   -webkit-margin-end: 20px;
   padding: 0px;
@@ skipping 26 matching lines @@
 }
 
 .tabs.horizontal li.active
 {
   border-bottom: 2px solid #1E8728;
   color: black;
   font-weight: 600;
   padding-bottom: 10px;
 }
 
-.icon,
-button[role="checkbox"],
-.table button.delete,
-#content-help a::before,
-#dialog-close::before,
+.icon, .table button[role="checkbox"], .table button.delete,
+#content-help a::before, #dialog-close::before,
 #custom-filters-add button::after,
 #dialog-body button::before
 {
   background-image: url(options-sprite.png);
   display: inline-block;
 }
 
 .icon-add
 {
   background-position: -0px -0px;
@@ skipping 613 matching lines @@
 #other-language .button-add::before
 {
   display: none;
 }
 
 #other-language .display
 {
   -webkit-margin-start: 10px;
   -moz-margin-start: 10px;
 }