--- a/dom/base/CustomElementsRegistry.h
+++ b/dom/base/CustomElementsRegistry.h
@@ -117,20 +117,16 @@ struct CustomElementDefinition
   JS::Heap<JSObject *> mConstructor;
 
   // The prototype to use for new custom elements of this type.
   JS::Heap<JSObject *> mPrototype;
 
   // The lifecycle callbacks to call for this custom element.
   nsAutoPtr<mozilla::dom::LifecycleCallbacks> mCallbacks;
 
-  // Whether we're currently calling the created callback for a custom element
-  // of this type.
-  bool mElementIsBeingCreated;
-
   // A construction stack.
   // TODO: Bug 1287348 - Implement construction stack for upgrading an element
 
   // The document custom element order.
   uint32_t mDocOrder;
 };
 
 class CustomElementsRegistry final : public nsISupports,