Merge "Wait for shell drop target to be ready for handling drags in tests" into udc-dev am: 52cc03e42c am: d03767df3d

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/22935091

Change-Id: I9e6e787a2f15472261caf2e990141876fb261bbb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>