--- a/dom/html/HTMLFormElement.cpp
+++ b/dom/html/HTMLFormElement.cpp
@@ -855,54 +855,26 @@ nsresult HTMLFormElement::NotifySubmitOb
     if (NS_FAILED(rv)) {
       return rv;
     }
     if (*aCancelSubmit) {
       return NS_OK;
     }
   }
 
-  // Notify observers that the form is being submitted.
-  nsCOMPtr<nsIObserverService> service =
-      mozilla::services::GetObserverService();
-  if (!service) return NS_ERROR_FAILURE;
-
-  nsCOMPtr<nsISimpleEnumerator> theEnum;
-  nsresult rv = service->EnumerateObservers(
-      aEarlyNotify ? NS_EARLYFORMSUBMIT_SUBJECT : NS_FORMSUBMIT_SUBJECT,
-      getter_AddRefs(theEnum));
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  if (theEnum) {
-    nsCOMPtr<nsISupports> inst;
-    *aCancelSubmit = false;
-
-    // XXXbz what do the submit observers actually want?  The window
-    // of the document this is shown in?  Or something else?
-    // sXBL/XBL2 issue
-    nsCOMPtr<nsPIDOMWindowOuter> window = OwnerDoc()->GetWindow();
-
-    bool loop = true;
-    while (NS_SUCCEEDED(theEnum->HasMoreElements(&loop)) && loop) {
-      theEnum->GetNext(getter_AddRefs(inst));
-
-      nsCOMPtr<nsIFormSubmitObserver> formSubmitObserver(
-          do_QueryInterface(inst));
-      if (formSubmitObserver) {
-        rv = formSubmitObserver->Notify(
-            this, window ? window->GetCurrentInnerWindow() : nullptr,
-            aActionURL, aCancelSubmit);
-        NS_ENSURE_SUCCESS(rv, rv);
-      }
-      if (*aCancelSubmit) {
-        return NS_OK;
-      }
-    }
+  bool defaultAction = true;
+  nsresult rv = nsContentUtils::DispatchEventOnlyToChrome(
+      OwnerDoc(), static_cast<nsINode*>(this),
+      aEarlyNotify ? NS_LITERAL_STRING("DOMFormBeforeSubmit")
+                   : NS_LITERAL_STRING("DOMFormSubmit"),
+      CanBubble::eYes, Cancelable::eYes, &defaultAction);
+  *aCancelSubmit = !defaultAction;
+  if (*aCancelSubmit) {
+    return NS_OK;
   }
-
   return rv;
 }
 
 nsresult HTMLFormElement::WalkFormElements(
     HTMLFormSubmission* aFormSubmission) {
   // This shouldn't be called recursively, so use a rather large value
   // for the preallocated buffer.
   AutoTArray<RefPtr<nsGenericHTMLFormElement>, 100> sortedControls;

--- a/dom/html/nsIFormSubmitObserver.idl
+++ b/dom/html/nsIFormSubmitObserver.idl
@@ -11,19 +11,15 @@ interface nsIURI;
 interface nsIArray;
 
 webidl HTMLFormElement;
 webidl Element;
 
 [scriptable, uuid(867cb7e7-835d-408b-9788-d2834d284e03)]
 interface nsIFormSubmitObserver: nsISupports
 {
-  void notify(in HTMLFormElement formNode, in mozIDOMWindow window, in nsIURI actionURL, out boolean cancelSubmit);
-
   void notifyInvalidSubmit(in HTMLFormElement formNode,
                            in Array<Element> invalidElements);
 };
 
 %{C++
-#define NS_FORMSUBMIT_SUBJECT "formsubmit"
-#define NS_EARLYFORMSUBMIT_SUBJECT "earlyformsubmit"
 #define NS_INVALIDFORMSUBMIT_SUBJECT "invalidformsubmit"
 %}