When DatePicker has focus, the App cannot be exited with Cmd+Q shortcut.
Steps to observe the issue:

1. Launch Ensemble
2. Navigate to DatePicker sample
3. Click on the DatePicker TextField
4. Press Cmd+Q => App does not quit
5. Open DatePicker popup menu
6. Press Cmd+Q => App does not quit
7. Click on the search text box on right top corner, so that DatePicker looses focus
8. Press Cmd+Q => App quits