Issue 5864 - Remove previous style sheet before adding one

polyfill.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present 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 19 matching lines @@
     "storage.local.get",
     "storage.local.remove",
     "storage.local.set",
     "storage.managed.get",
     "tabs.create",
     "tabs.get",
     "tabs.getCurrent",
     "tabs.insertCSS",
     "tabs.query",
     "tabs.reload",
+    "tabs.removeCSS",
     "tabs.sendMessage",
     "tabs.update",
     "webNavigation.getAllFrames",
     "webRequest.handlerBehaviorChanged",
     "windows.create",
     "windows.update"
   ];
 
   // Since we add a callback for all messaging API calls in our wrappers,
   // Chrome assumes we're interested in the response; when there's no response,
@@ skipping 171 matching lines @@
 
   // Workaround since HTMLCollection, NodeList, StyleSheetList, and CSSRuleList
   // didn't have iterator support before Chrome 51.
   // https://bugs.chromium.org/p/chromium/issues/detail?id=401699
   for (let object of [HTMLCollection, NodeList, StyleSheetList, CSSRuleList])
   {
     if (!(Symbol.iterator in object.prototype))
       object.prototype[Symbol.iterator] = Array.prototype[Symbol.iterator];
   }
 }