Sync some event interfaces with the HTML spec

Source/core/events/AutocompleteErrorEvent.idl

Index: Source/core/events/AutocompleteErrorEvent.idl
diff --git a/Source/core/events/AutocompleteErrorEvent.idl b/Source/core/events/AutocompleteErrorEvent.idl
index 7853cb1ec27912c76da083a8f400723cd25ac0c7..a65f1eed98361bc8630d2e57c88dc1bf84a785ec 100644
--- a/Source/core/events/AutocompleteErrorEvent.idl
+++ b/Source/core/events/AutocompleteErrorEvent.idl
@@ -24,9 +24,10 @@
 
 // https://html.spec.whatwg.org/multipage/forms.html#the-autocompleteerrorevent-interface
 
+enum AutocompleteErrorReason { "" /* empty string */, "cancel", "disabled", "invalid" };
+
 [
     Constructor(DOMString type, optional AutocompleteErrorEventInit eventInitDict),
 ] interface AutocompleteErrorEvent : Event {
-    readonly attribute DOMString reason;
+    readonly attribute AutocompleteErrorReason reason;
 };
-