Use new syntax for DOMException. (#780)

Author: Ms2ger

index.bs

@@ -14129,9 +14129,10 @@ fragment:
 
 <pre class="idl">
 [Exposed=(Window,Worker),
- Constructor(optional DOMString message = "", optional DOMString name = "Error"),
  Serializable]
 interface DOMException { // but see below note about ECMAScript binding
+  constructor(optional DOMString message = "", optional DOMString name = "Error");
+
   readonly attribute DOMString name;
   readonly attribute DOMString message;
   readonly attribute unsigned short code;