Logging the time that we use for the current events range

It appears that sometimes logcat -d returns events that are earlier than
that time, but we need to be sure.

Example:
ACTION_UP from the previous TAPL method:
https://sponge.corp.google.com/target?show=FAILED&sortBy=STATUS&id=1aceab23-6d2a-4b2d-9630-47a74cafe7b9&target=com.google.android.apps.nexuslauncher.tests

Change-Id: Ib83e1cc01402ef638f8ac8a0862e16c5773b82cd