update elements and fix some bugs

lib/iron_a11y_keys_behavior.dart

Index: lib/iron_a11y_keys_behavior.dart
diff --git a/lib/iron_a11y_keys_behavior.dart b/lib/iron_a11y_keys_behavior.dart
index 0f06fa5a405768ad87075e7365a3e84e47d5f94a..6c5155d0eda2e0ef2a8624d885905596c69a1b66 100644
--- a/lib/iron_a11y_keys_behavior.dart
+++ b/lib/iron_a11y_keys_behavior.dart
@@ -31,6 +31,11 @@ abstract class IronA11yKeysBehavior implements CustomElementProxyMixin {
   get keyEventTarget => jsElement[r'keyEventTarget'];
   set keyEventTarget(value) { jsElement[r'keyEventTarget'] = (value is Map || (value is Iterable && value is! JsArray)) ? new JsObject.jsify(value) : value;}
 
+  /// If true, this property will cause the implementing element to
+  /// automatically stop propagation on any handled KeyboardEvents.
+  bool get stopKeyboardEventPropagation => jsElement[r'stopKeyboardEventPropagation'];
+  set stopKeyboardEventPropagation(bool value) { jsElement[r'stopKeyboardEventPropagation'] = value; }
+
   /// Can be used to imperatively add a key binding to the implementing
   /// element. This is the imperative equivalent of declaring a keybinding
   /// in the `keyBindings` prototype property.