Improve enter and dismiss transition by using snapshot

If reparent and bounds changed case, we have snapshot on those
transition change and we could use them to do cross fade animation.
And it could reduce flicker caused by black screen if we only do
fade-in animation(black screen on start of fade-in).

Bug: 245472831
Fix: 280013136
Fix: 281769738
Test: manual
Test: pass existing tests
Change-Id: I145f777ba5ec100be2ecbe4759a8c3d59fe59b27