Add Drm playback tests to TreeHugger presubmit.

Most players are using exoplayer, and Widevine DRM is
required. These CL adds three tests to TreeHugger
presubmit to reduce regression.

This CL adds three tests to presubmit process,
most time is spent running one exoplayer test.

Test: time atest

bug: 148287604
Change-Id: Ia550ad82207f2f85bb38a560a47eef4a087fb810