After 252266@main, it is now possible to merge ConcreteImageBuffer into ImageBuffer since all the ImageBuffer subclasses are actually subclasses of ConcreteImageBuffer.
<rdar://problem/96837190>
Pull request: https://github.com/WebKit/WebKit/pull/2298
Committed 252369@main (aabcd6f6cd3b): <https://commits.webkit.org/252369@main> Reviewed commits have been landed. Closing PR #2298 and removing active labels.