Fixed an issue where notifications wouldn't animate on height change

When switching between templates, the old intrinsic height was 0
before the layout, which suppressed the height animation. We're now
also animating if the previous height was 0 but the view already
had a height.

Fixes: 187979400
Test: add gmail notification, archive, observe animation
Change-Id: I3fa2edf9a39b586a685a96f89a74ead597143981