Issue 4298 - Enforce 'display: none' for ElemHide

include.preload.js

Index: include.preload.js
diff --git a/include.preload.js b/include.preload.js
index bb6b97a01c6d5cc7bff5dc9ab8ca8285880f89bc..5133b364532cb718528401ba64c90f16b3aee048 100644
--- a/include.preload.js
+++ b/include.preload.js
@@ -347,6 +347,9 @@ function reinjectStyleSheetWhenRemoved(document, style)
     {
       parentNode.appendChild(style);
 
+      // Our style element's sheet is sometimes lost when the element is removed
+      // from the DOM. A new empty sheet is then created in its place so we have
+      // to restore the rules ourselves.
       if (style.sheet.rules.length == 0)
       {
         for (var i = 0; i < rules.length; i += 1)
@@ -359,6 +362,7 @@ function reinjectStyleSheetWhenRemoved(document, style)
             var style = document.getElementById(id) ||
                         document.documentElement.shadowRoot.getElementById(id);
             style.removeAttribute("id");
+
             Object.defineProperty(style.sheet, "disabled",
                                   {value: false, enumerable: true});
           }, id
@@ -394,28 +398,36 @@ function protectStyleSheet(document, style)
                 document.documentElement.shadowRoot.getElementById(id);
     style.removeAttribute("id");
 
-    var i;
-    var disableables = [style, style.sheet];
-    for (i = 0; i < disableables.length; i += 1)
-      Object.defineProperty(disableables[i], "disabled",
-                            {value: false, enumerable: true});
+    Object.defineProperty(style, "disabled",
+                          {value: false, enumerable: true});
+    Object.defineProperty(style.sheet, "disabled",
+                          {value: false, enumerable: true});
 
-    var methods = ["deleteRule", "removeRule"];
-    for (i = 0; i < methods.length; i += 1)
+    function wrapMethods(methodNames, descKey, defaultReturnValue)
     {
-      if (methods[i] in CSSStyleSheet.prototype)
+      for (var i = 0; i < methodNames.length; i += 1)
       {
-        (function(method)
+        if (methodNames[i] in CSSStyleSheet.prototype)
         {
-          var original = CSSStyleSheet.prototype[method];
-          CSSStyleSheet.prototype[method] = function(index)
+          (function(method)
           {
-            if (this != style.sheet)
-              original.call(this, index);
-          };
-        }(methods[i]));
+            var desc = Object.getOwnPropertyDescriptor(CSSStyleSheet.prototype,
+                                                       method);
+            var original = desc[descKey];
+            desc[descKey] = function()
+            {
+              if (this != style.sheet)
+                return original.apply(this, arguments);
+              return defaultReturnValue;
+            };
+            Object.defineProperty(CSSStyleSheet.prototype, method, desc);
+          }(methodNames[i]));
+        }
       }
     }
+
+    wrapMethods(["deleteRule", "removeRule"], "value");
+    wrapMethods(["rules", "cssRules"], "get", []);
   };
 
   injectJS(protector, id);