fix(backdrop): disable tap longer after backdrop close

To prevent unwanted clicks from happening, such as an input getting
focus after clicking “OK” on a popup, keep the backdrop visible for a
longer period of time. The simulated click is what closes the popup’s
backdrop, but the native click will still happen 300ms later, which may
cause another input to receive focus. Closes #1536

js/angular/service/backdrop.js

@@ -76,7 +76,7 @@ function($document) {
       el.removeClass('active');
       setTimeout(function() {
         !backdropHolds && el.removeClass('visible');
-      }, 100);
+      }, 400);
     }
   }