update elements and fix some bugs

lib/iron_autogrow_textarea.dart

 // DO NOT EDIT: auto-generated with `pub run custom_element_apigen:update`
 
 /// Dart API for the polymer element `iron_autogrow_textarea`.
 @HtmlImport('iron_autogrow_textarea_nodart.html')
 library polymer_elements.lib.src.iron_autogrow_textarea.iron_autogrow_textarea;
 
 import 'dart:html';
 import 'dart:js' show JsArray, JsObject;
 import 'package:web_components/web_components.dart';
 import 'package:polymer_interop/polymer_interop.dart';
 import 'iron_form_element_behavior.dart';
 import 'iron_validatable_behavior.dart';
 import 'iron_control_state.dart';
 import 'iron_flex_layout/classes/iron_flex_layout.dart';
 
 /// `iron-autogrow-textarea` is an element containing a textarea that grows in height as more
 /// lines of input are entered. Unless an explicit height or the `maxRows` property is set, it will
 /// never scroll.
 ///
 /// Example:
 ///
 ///     <iron-autogrow-textarea></iron-autogrow-textarea>
 ///
 /// Because the `textarea`'s `value` property is not observable, you should use
 /// this element's `bind-value` instead for imperative updates.
+///
+/// ### Styling
+/// The following custom properties and mixins are available for styling:
+/// Custom property | Description | Default
+/// ----------------|-------------|----------
+/// `--iron-autogrow-textarea` | Mixin applied to the textarea | `{}`
 @CustomElementProxy('iron-autogrow-textarea')
 class IronAutogrowTextarea extends HtmlElement with CustomElementProxyMixin, PolymerBase, IronFormElementBehavior, IronValidatableBehavior, IronControlState {
   IronAutogrowTextarea.created() : super.created();
   factory IronAutogrowTextarea() => new Element.tag('iron-autogrow-textarea');
 
   /// Bound to the textarea's `autocomplete` attribute.
   String get autocomplete => jsElement[r'autocomplete'];
   set autocomplete(String value) { jsElement[r'autocomplete'] = value; }
 
   /// Bound to the textarea's `autofocus` attribute.
@@ skipping 51 matching lines @@
   /// The value for this input, same as `bindValue`
   String get value => jsElement[r'value'];
   set value(String value) { jsElement[r'value'] = value; }
 
   /// Returns true if `value` is valid. The validator provided in `validator`
   /// will be used first, if it exists; otherwise, the `textarea`'s validity
   /// is used.
   bool validate() =>
       jsElement.callMethod('validate', []);
 }