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 0c8935a745eb8fc7ce9d07111c34bc0f6befd3e9..bb6b97a01c6d5cc7bff5dc9ab8ca8285880f89bc 100644
--- a/include.preload.js
+++ b/include.preload.js
@@ -339,11 +339,32 @@ function reinjectStyleSheetWhenRemoved(document, style)
   if (!MutationObserver)
     return null;
 
+  var rules = style.sheet.rules;
   var parentNode = style.parentNode;
   var observer = new MutationObserver(function()
   {
     if (style.parentNode != parentNode)
+    {
       parentNode.appendChild(style);
+
+      if (style.sheet.rules.length == 0)
+      {
+        for (var i = 0; i < rules.length; i += 1)
+          style.sheet.addRule(rules[i].selectorText, "display: none !important;");
+
+        style.id = id;
+        injectJS(
+          function(id)
+          {
+            var style = document.getElementById(id) ||
+                        document.documentElement.shadowRoot.getElementById(id);
+            style.removeAttribute("id");
+            Object.defineProperty(style.sheet, "disabled",
+                                  {value: false, enumerable: true});
+          }, id
+        );
+      }
+    }
   });
 
   observer.observe(parentNode, {childList: true});