Issue 4191 - Restore rules for reinjected stylesheets

include.preload.js

Index: include.preload.js
diff --git a/include.preload.js b/include.preload.js
index f4ab60be781c88c27079d7df6f1c4e77a430188d..cbe3b0f9883e398b37e22627eef3c280a2e636ff 100644
--- a/include.preload.js
+++ b/include.preload.js
@@ -334,22 +334,6 @@ ElementHidingTracer.prototype = {
   }
 };
 
-function reinjectStyleSheetWhenRemoved(document, style)
-{
-  if (!MutationObserver)
-    return null;
-
-  var parentNode = style.parentNode;
-  var observer = new MutationObserver(function()
-  {
-    if (style.parentNode != parentNode)
-      parentNode.appendChild(style);
-  });
-
-  observer.observe(parentNode, {childList: true});
-  return observer;
-}
-
 function runInPage(fn, arg)
 {
   var script = document.createElement("script");
@@ -360,33 +344,6 @@ function runInPage(fn, arg)
   document.documentElement.removeChild(script);
 }
 
-function protectStyleSheet(document, style)
-{
-  style.id = id;

[Sebastian Noack, 2016/08/11 12:38:57]

Since the id is only used once (for the WebSocket) now, mind moving the code
creating it, from the global scope to where it is used.

[kzar, 2016/08/11 12:48:18]

Done.

-
-  runInPage(function(id)
-  {
-    var style = document.getElementById(id) ||
-                document.documentElement.shadowRoot.getElementById(id);
-    style.removeAttribute("id");
-
-    var disableables = [style, style.sheet];
-    for (var i = 0; i < disableables.length; i++)
-      Object.defineProperty(disableables[i], "disabled",
-                            {value: false, enumerable: true});
-
-    ["deleteRule", "removeRule"].forEach(function(method)
-    {
-      var original = CSSStyleSheet.prototype[method];
-      CSSStyleSheet.prototype[method] = function(index)
-      {
-        if (this != style.sheet)
-          original.call(this, index);
-      };
-    });
-  }, id);
-}
-
 // Neither Chrome[1] nor Safari allow us to intercept WebSockets, and therefore
 // some ad networks are misusing them as a way to serve adverts and circumvent
 // us. As a workaround we wrap WebSocket, preventing blocked WebSocket
@@ -499,6 +456,22 @@ function init(document)
   {
     shadow = document.documentElement.createShadowRoot();
     shadow.appendChild(document.createElement("shadow"));
+
+    // Stop the website from messing with our shadowRoot
+    runInPage(function()

[Sebastian Noack, 2016/08/11 12:48:11]

You have to pass the document to runInPage(), to make sure that it gets injected
into the right document.

[kzar, 2016/08/11 13:04:46]

Done.

+    {
+      var ourShadowRoot = document.documentElement.shadowRoot;
+      var desc = Object.getOwnPropertyDescriptor(Element.prototype, "shadowRoot");
+      var shadowRoot = Function.prototype.call.bind(desc.get);
+
+      Object.defineProperty(Element.prototype, "shadowRoot", {
+        conifgurable: true, enumerable: true, get: function()
+        {
+          var shadow = shadowRoot(this);
+          return shadow === ourShadowRoot ? null : shadow;

[Sebastian Noack, 2016/08/11 12:38:57]

Nit: As per Mozilla's coding practices, we prefer === over ==.

[Sebastian Noack, 2016/08/11 12:42:37]

(The other way around, I meant, == is preferred over ===)

[kzar, 2016/08/11 12:48:18]

Done.

+        }
+      });
+    }, "");

[Sebastian Noack, 2016/08/11 12:38:57]

Nit: I'd rather pass null, than creating an empty string.

[kzar, 2016/08/11 12:48:18]

Done.

   }
 
   function addElemHideSelectors(selectors)
@@ -521,9 +494,6 @@ function init(document)
       // <style> element to the shadow DOM.
       if (!style.sheet)
         return;
-
-      observer = reinjectStyleSheetWhenRemoved(document, style);
-      protectStyleSheet(document, style);
     }
 
     // If using shadow DOM, we have to add the ::content pseudo-element