Merge from Widevine repo of http://go/wvgerrit/100110
The unit test TimeRollbackPrevention was broken for several
reasons. This CL reduces the test to its most basic functionality and
updates it to be compatible with a v16 oemcrypto.
This CL also adjusts the fake clock used by the buildbot to fake
sleeping backwards, so that the TimeRollbackPrevention test can also
be run on the buildbot.
Bug: 155773482
Bug: 79422351
Test: unit tests on buildbot, and on flame w/v16 modmock
Change-Id: I3027018b17b738281989e63ae6b0729757217d05
75575418d0