During a positive `animationDelay` with `animationFillMode: backwards`,
`CSSAnimationsRegistry::applyViewAnimationsStyle` computed the backwards
fill but wrote it only to `updatesRegistry_`, not to the per-frame delta
batch. The registry is committed to the tree only on a React-source commit
(via the commit hook), so during a pure delay window with no re-render the
fill was never painted and the view kept its base style - e.g. a width-less
flex child stretched to full width instead of showing the from-keyframe 0.

Enqueue the computed fill into the delta batch as well (as the running
update path and CSS transitions already do), so the CSS loop commits it
without needing a React commit.

4.4/4.5 fixed this as part of the larger OperationsLoop rewrite (#9248),
which is impractical to backport to 4.3 wholesale; this is the minimal port.

Removed comments explaining the commit behavior of the registry during animation delays.