Merge "re-organize recents transition code for future changes" into udc-dev...

Merge "re-organize recents transition code for future changes" into udc-dev am: ca939575 am: 1f5ec79f

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/21497556



Change-Id: Ia6f8cbce01f9e4d478435e047e91fdb9a5e51945
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>