Hedger Wang 809a2dc1d6 [Navigator: Prevent user from over-popping the routes.
Summary:
If user taps the back button quickly, the app crashes becuase "pop"
internally only checks `this.state.presentedIndex` which does not
always update when transtion happens.

This diff addresses this issue.
2015-07-29 11:42:34 -08:00
..