message: Changed onBack to match onNavigate syntax
diff: @@ -4,22 +4,9 @@ import { BackAndroid } from 'react-native';
  class NavigationBackAndroid extends React.Component<any, any> {
  private url: string;
  - private onBack = () => {
  - var stateNavigator = this.getStateNavigator();
  - if (this.url === stateNavigator.stateContext.url) {
  - var listener = this.props.navigating;
  - var navigate = true;
  - if (listener)
  - navigate = listener();
  - var canNavigateBack = stateNavigator.canNavigateBack(1);
  - if (navigate && canNavigateBack)
  - stateNavigator.navigateBack(1);
  - return !navigate || canNavigateBack;
  - }
  - return false;
  - }
  constructor(props, context) {
  super(props, context);
  + this.onBack = this.onBack.bind(this);
  this.url = this.getStateNavigator().stateContext.url;
  }
  static contextTypes = {
  @@ -34,6 +21,20 @@ class NavigationBackAndroid extends React.Component<any, any> {
  componentWillUnmount() {
  BackAndroid.removeEventListener('hardwareBackPress', this.onBack);
  }
  + onBack() {
  + var stateNavigator = this.getStateNavigator();
  + if (this.url === stateNavigator.stateContext.url) {
  + var listener = this.props.navigating;
  + var navigate = true;
  + if (listener)
  + navigate = listener();
  + var canNavigateBack = stateNavigator.canNavigateBack(1);
  + if (navigate && canNavigateBack)
  + stateNavigator.navigateBack(1);
  + return !navigate || canNavigateBack;
  + }
  + return false;
  + }
  render() {
  return null;
  }
  