Issue 6803 - Implement readd snippet

lib/content/snippets.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 149 matching lines @@
  * @param {...*} [args] The arguments to log.
  */
 function trace(...args)
 {
   // We could simply use console.log here, but the goal is to demonstrate the
   // usage of snippet dependencies.
   log(...args);
 }
 
 exports.trace = makeInjector(trace, log);
+
+// This is an implementation of the uabinject-defuser technique used by uBlock
+// Origin
+// https://github.com/uBlockOrigin/uAssets/blob/c091f861b63cd2254b8e9e4628f6bdcd89d43caa/filters/resources.txt#L640
+function uabinjectDefuser()
+{
+  window.trckd = true;
+  window.uabpdl = true;
+  window.uabInject = true;
+  window.uabDetect = true;
+}
+
+exports["uabinject-defuser"] = makeInjector(uabinjectDefuser);
 
 /**
  * Hides any HTML element or one of its ancestors matching a CSS selector if
  * the text content of the element's shadow contains a given string.
  *
  * @param {string} search The string to look for in every HTML element's
  *   shadow.
  * @param {string} selector The CSS selector that an HTML element must match
  *   for it to be hidden.
  */
@@ skipping 61 matching lines @@
 
       return root;
     }
   });
 }
 
 exports["hide-if-shadow-contains"] = makeInjector(hideIfShadowContains,
                                                   hideElement);
 
 /**
- * Untrashes a document by readding removed elements that match a CSS selector.
- *
- * @param {string} selector The CSS selector that a removed element should
+ * Readds to the document any removed HTML elements that match a CSS selector.
+ *
+ * @param {string} selector The CSS selector that a removed HTML element should
  *   match for it to be added back.
- * @param {string?} [parentSelector] The CSS selector that a removed element's
- *   former parent should match for it to be added back.
- */
-function untrash(selector, parentSelector = null)
+ * @param {string?} [parentSelector] The CSS selector that a removed HTML
+ *   element's former parent should match for it to be added back.
+ */
+function readd(selector, parentSelector = null)
 {
   observe(document, {childList: true, subtree: true}, mutation =>
   {
     if (mutation.removedNodes &&
-        (!parentSelector || mutation.target.matches(parentSelector)))
+        (!parentSelector || (mutation.target instanceof Element &&
+                             mutation.target.matches(parentSelector))))
     {
       for (let node of mutation.removedNodes)
       {
         if (node instanceof HTMLElement && node.matches(selector))
         {
           // We don't have the location of the element in its former parent,
           // but it's usually OK to just add it at the end.
           mutation.target.appendChild(node);
         }
       }
     }
   });
 }
 
-exports.untrash = untrash;
+exports.readd = readd;