Merge "Override DreamActivity enter and exit animations" into rvc-dev am: 1255a2d20b am: d47b9b1a27

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/11308359

Change-Id: I1ff410e3d6d02f2dae9a13e4a136c950b2308298