Add utility method to run a native JS function

gwtquery-core/src/main/java/com/google/gwt/query/client/js/JsUtils.java

@@ -228,6 +228,14 @@ public class JsUtils {
     }
   }
 
+  /**
+   * Execute a native javascript function.
+   */
+  public static <T> T exec(JavaScriptObject jsFunction, Object... args) {
+    assert isFunction(jsFunction);
+    return jsni(jsFunction, "call", jsFunction, args);
+  }
+
   /**
    * Assign a function to a property of the window object.
    */