[automerger skipped] Mark an ActivityThreadTest as flaky am: 0492d8fe -s ours am: e84a831f -s ours am: 11fef20e -s ours

am skip reason: Merged-In I2452db8523438de4d06c938c3c3fa1d8a9aa0f4e with SHA-1 0b6ea59f is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15336321

Change-Id: I4d2e42d995be09f698ca2662de04e4fe65259b69