Before this change, we'd skip storing the new ComputedProperties in
Element::recompute_style() if there was no invalidation needed.
This caused us to lose the information about which properties are
inherited and/or important (which is also carried by ComputedProperties,
but doesn't affect invalidation).
Consequently, we'd then fail to recompute inherited styles, since that
mechanism depends on this data.
The fix is simply to always store the new ComputedProperties.
