Merge "Fix flicker when task move to back" into sc-v2-dev am: d2f034f1d5 am: cfb5de081e

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15810446

Change-Id: I903bde406235a63368e8ee74c30f4c57305cfbc0