update elements and fix some bugs

lib/iron_form_element_behavior.dart

 // DO NOT EDIT: auto-generated with `pub run custom_element_apigen:update`
 
 /// Dart API for the polymer element `iron_form_element_behavior`.
 @HtmlImport('iron_form_element_behavior_nodart.html')
 library polymer_elements.lib.src.iron_form_element_behavior.iron_form_element_behavior;
 
 import 'dart:html';
 import 'dart:js' show JsArray, JsObject;
 import 'package:web_components/web_components.dart';
 import 'package:polymer_interop/polymer_interop.dart';
 
 /// Polymer.IronFormElementBehavior enables a custom element to be included
 ///   in an `iron-form`.
 @BehaviorProxy(const ['Polymer', 'IronFormElementBehavior'])
 abstract class IronFormElementBehavior implements CustomElementProxyMixin {
 
   /// The name of this element.
   String get name => jsElement[r'name'];
   set name(String value) { jsElement[r'name'] = value; }
 
   /// Set to true to mark the input as required. If used in a form, a
   /// custom element that uses this behavior should also use
   /// Polymer.IronValidatableBehavior and define a custom validation method.
   /// Otherwise, a `required` element will always be considered valid.
-  /// It's also strongly recomended to provide a visual style for the element
-  /// when it's value is invalid.
+  /// It's also strongly recommended to provide a visual style for the element
+  /// when its value is invalid.
   bool get required => jsElement[r'required'];
   set required(bool value) { jsElement[r'required'] = value; }
 
   /// The value for this element.
   String get value => jsElement[r'value'];
   set value(String value) { jsElement[r'value'] = value; }
 }