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

Merge "Set alpha to 0 on attach to avoid flicker at transition start." into udc-dev am: dc472531 am: 8c98d4e9 am: 77500885 am: 2c32b852

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



Change-Id: I66120dac599c7b89dfa8ead683e4bf6e8bf33d0d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>