Check ProjectBackwards property for childrens after children's syncProperties().

Children's ProjectBackwards is not applied. So it's skipped so far.
This fix a problem that first ripple bg is not shown properly.
:It uses ProjectBackwards&ProjectReceiver concept.

For deeper understanding, refer to
https://partnerissuetracker.corp.google.com/issues/173476923

Test: aosp build , Full test on samsung mobile device
Change-Id: I36a1bc95673093ba2c886703974bf672c53c2cf3