message: Evaluated crumbs upfront
diff: @@ -99,6 +99,7 @@ class NavigationMotion extends React.Component<any, any> {
  render() {
  var {unmountedStyle, mountedStyle, crumbStyle, style, children, duration, sharedElementMotion} = this.props;
  var {stateContext} = this.getStateNavigator();
  + var crumbs = stateContext.crumbs;
  var navigationProgress = 0;
  return (stateContext.state &&
  <Motion
  @@ -111,8 +112,7 @@ class NavigationMotion extends React.Component<any, any> {
  onRest={({key}) => this.clearScene(key)}>
  {tweenStyles => (
  tweenStyles.map(({key, data: {scene, state, data, url}, progress, style: tweenStyle}) => {
  - if (stateContext.crumbs.length === key)
  - navigationProgress = progress;
  + navigationProgress = crumbs.length === key ? progress : navigationProgress;
  return (children as any)(tweenStyle, scene, key, state, data)
  }).concat(
  sharedElementMotion && sharedElementMotion({
  