Fix flashing artifacts caused by invalidation bugs

Therea re 2 fixes here:
- We sometimes cleared a flag in ViewAncestor too soon that controlled
how invalidated areas were redrawn (related to whether the invalidates
happened on opaque views or not).
- TransitionDrawable was always setting/restoring alpha values on its
drawables every time it was drawn. setAlpha on BitmapDrawable causes
an invalidation, so essentially this was an infinite invalidation/redrawing
loop. The fix was to notice when the animation was done and to simply
draw the appropriate drawable[s].

Change-Id: I1849a5a909b0039a0e9bce0aa3cfc33c50f8f854