Merge "Add test mechanism to check whether the shell drop target window has drawn" into udc-dev am: d4760a4d am: f7f174be am: 58c261fe

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/22939180



Change-Id: I70e46a0655028b67d953a55dbd62959eb96f62f2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>