Experimental: Notification event viewer.

Long-term goals: help users identify the package responsible
for any notification, and then (eventually) control all
notifications in a single place.

Until full notification history is available in the
NotificationManagerService, all we can do is dig
through the EventLog.

Bug: 5547401 (and others)
Change-Id: I3f18de739f8958db23f18429272ca7e5377e0239
5 files changed