update elements and fix some bugs

lib/src/iron-list/test/helpers.html

Index: lib/src/iron-list/test/helpers.html
diff --git a/lib/src/iron-list/test/helpers.html b/lib/src/iron-list/test/helpers.html
index eaa43ce05c71a5f824efd7ae096436a7b1c09456..07f240020d25ee91320fee210c3cd4949cc3e734 100644
--- a/lib/src/iron-list/test/helpers.html
+++ b/lib/src/iron-list/test/helpers.html
@@ -72,4 +72,23 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
     var listRect = list.getBoundingClientRect();
     return document.elementFromPoint(listRect.left + 1, listRect.top + listRect.height - 1);
   }
+
+  function isFullOfItems(list) {
+    var listRect = list.getBoundingClientRect();
+    var listHeight = listRect.height - 1;
+    var item, y = listRect.top + 1;
+    // IE 10 & 11 doesn't render propertly :(
+    var badPixels = 0;
+    while (y < listHeight) {
+      item = document.elementFromPoint(listRect.left + 1, y);
+      if (item.parentNode && !item.parentNode._templateInstance) {
+        badPixels++;
+      }
+      if (badPixels > 3) {
+        return false;
+      }
+      y += 2;
+    }
+    return true;
+  }
 </script>