[automerger] Rework thumbnail cleanup am: 0dc23f95a1 skipped: 75767d1e3c am: 6720ea0b94 am: 16ee12ac68 am: d08bb4b174
am: b3f50c9ccb  -s ours

Change-Id: I1b214134e879310733ee40b138c29cfc0a78b32e