anchor.diff:  
   var mainComponent = react.registerComponent(() => new _MainComponent());
   
  -class _ContextComponent extends react.Component2 {
  +class _ContextComponent extends react.Component {
     @override
     Iterable<String> get childContextKeys => const ['foo', 'bar', 'renderCount'];
   
  
positive.code: import "package:react/react.dart" as react;
  import "package:react/react_dom.dart" as react_dom;
  
  class _HelloComponent extends react.Component2 {
    void componentWillReceiveProps(nextProps) {
      if (nextProps["name"].length > 20) {
        print("Too long Hello!");
  
negative.code: 
  var helloGreeter = react.registerComponent(() => new _HelloGreeter());
  
  class _CheckBoxComponent extends react.Component {
    getInitialState() => {"checked": false};
  
    change(e) {
  