Fix the CG_DISPLAY_LIST_BACKED_IMAGE_BUFFER build
<rdar://problem/104990302>
Pull request: https://github.com/WebKit/WebKit/pull/9581
Committed 259797@main (fe80d6ae2624): <https://commits.webkit.org/259797@main> Reviewed commits have been landed. Closing PR #9581 and removing active labels.