Merge "Merge "Set alpha to 0 on attach to avoid flicker at transition start."...

Merge "Merge "Set alpha to 0 on attach to avoid flicker at transition start." into udc-dev am: dc472531 am: bdb153f5 am: 29001875" into udc-qpr-dev-plus-aosp am: e3949d42

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23252176



Change-Id: Ia0f0760db9426f034e07ce0255c93a74daf09e11
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>