Bug 683614 - Fix typo in oninvalid event handler name in test. r=mounir

content/html/content/test/test_bug618948.html

@@ -74,7 +74,7 @@ i.onchange = function(event) {
 
 i.oninvalid = function(event) {
   eventHandler(event);
-  i.oninvad = null;
+  i.oninvalid = null;
   endTest();
 };