[automerger] Add tests for thumbnail cleanup am: 9245c121b6 am: 4d88079608 am: a49310632c am: dcf186ffe5 am: edaeab5e29 am: 3a41965be8 am: e51033c90e am: 096557beef am: 6909f22274 am: c3cf578553
am: 62a54c699c

Change-Id: I9cb284e3b3bb7eba747ef2710f5278b763fa182a