update elements and fix some bugs

lib/google_chart.dart

 // DO NOT EDIT: auto-generated with `pub run custom_element_apigen:update`
 
 /// Dart API for the polymer element `google_chart`.
 @HtmlImport('google_chart_nodart.html')
 library polymer_elements.lib.src.google_chart.google_chart;
 
 import 'dart:html';
 import 'dart:js' show JsArray, JsObject;
 import 'package:web_components/web_components.dart';
 import 'package:polymer_interop/polymer_interop.dart';
@@ skipping 109 matching lines @@
   /// <pre>
   ///   [{row:0,column:1}, {row:1, column:null}]
   /// </pre>
   List get selection => jsElement[r'selection'];
   set selection(List value) { jsElement[r'selection'] = (value != null && value is! JsArray) ? new JsObject.jsify(value) : value;}
 
   /// Sets the type of the chart.
   ///
   /// Should be one of:
   /// - `area`, `bar`, `bubble`, `candlestick`, `column`, `combo`, `geo`,
-  ///   `histogram`, `line`, `pie`, `scatter`, `stepped-area`
+  ///   `histogram`, `line`, `pie`, `scatter`, `stepped-area`, `treemap`
   ///
   /// See <a href="https://google-developers.appspot.com/chart/interactive/docs/gallery">Google Visualization API reference (Chart Gallery)</a> for details.
   String get type => jsElement[r'type'];
   set type(String value) { jsElement[r'type'] = value; }
 
   /// Draws the chart.
   ///
   /// Called automatically on first load and whenever one of the attributes
   /// changes. Can be called manually to handle e.g. page resizes.
   drawChart() =>
       jsElement.callMethod('drawChart', []);
 }