We include `WebAnimation.h` in `AcceleratedTimeline.cpp` even though we never deal with such objects in this code.
<rdar://problem/118881524>
Pull request: https://github.com/WebKit/WebKit/pull/20995
Committed 271227@main (92554e579aba): <https://commits.webkit.org/271227@main> Reviewed commits have been landed. Closing PR #20995 and removing active labels.