Merge "Supporting independent back nav while task embedded" into sc-v2-dev am:...

Merge "Supporting independent back nav while task embedded" into sc-v2-dev am: c3a85ce0 am: 66919a7c

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15390767

Change-Id: I767ee85a9ac388bc1a1ce562b13fd7a60a7c8f15