Fixes snooze button.

This change replaces the code in NotificationMenuRow which handles
button clicks by finding the index of the clicked view and looking up
the corresponding menu item by index.  Instead, we maintain a map of
views to menu items.

Test: manual
Change-Id: Ie493b575d57f7834b7be1096c5f114ed2be28ad3
Fixes: 120613998