Merge "[18/n] Letterbox Education: start dialog enter animation after all...

Merge "[18/n] Letterbox Education: start dialog enter animation after all shell transitions have finished" into tm-dev am: 5059dbde

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/17136515

Change-Id: I4ddb70134b5223fd52438f0f015e20019875a4de