Merge "Start blocking relayout sooner in exit/cancel enter desktop...

Merge "Start blocking relayout sooner in exit/cancel enter desktop transitions." into udc-qpr-dev am: c350b3fc am: bdfd2dce

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23519154



Change-Id: I2ea2e3550accb9be1c0601daa7489afca8f85b1e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>