[automerger skipped] Mark an ActivityThreadTest as flaky am: 0492d8fe am: 63177b91 -s ours am: 9978a945 -s ours

am skip reason: Merged-In I2452db8523438de4d06c938c3c3fa1d8a9aa0f4e with SHA-1 0492d8fe is already in history

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

Change-Id: Iff302b120f9e1717aeea6b336a0496b02daa158c