anchor.diff:        assert(manifest.fromHero != newManifest.fromHero);
         assert(manifest.toHero != newManifest.toHero);
   
  -      heroRect = new RectTween(
  -        begin: heroRect.evaluate(_proxyAnimation),
  -        end: _globalRect(newManifest.toHero.context),
  -      );
  +      heroRect = _doCreateRectTween(heroRect.evaluate(_proxyAnimation), _globalBoundingBoxFor(newManifest.toHero.context));
   
         if (newManifest.type == _HeroFlightType.pop)
           _proxyAnimation.parent = new ReverseAnimation(newManifest.animation);
  
positive.code:   }
  }
  
  // Everything known about a hero flight that's to be started or restarted.
  class _HeroFlightManifest {
    _HeroFlightManifest({
      @required this.type,
  
negative.code:       if (manifest.fromHero != newManifest.toHero) {
          manifest.fromHero.endFlight();
          newManifest.toHero.startFlight();
          heroRect = _doCreateRectTween(heroRect.end, _globalBoundingBoxFor(newManifest.toHero.context));
        } else {
          heroRect = _doCreateRectTween(heroRect.end, heroRect.begin);
        }
      } else {
        // A push or a pop flight is heading to a new route, i.e.
  