We shouldn't IdleExit a GPU Process if it has WebProcess clients that have DOM Rendering in the GPU Process enabled.
<rdar://110742027>
Pull request: https://github.com/WebKit/WebKit/pull/15269
Committed 265623@main (3db4e668e80e): <https://commits.webkit.org/265623@main> Reviewed commits have been landed. Closing PR #15269 and removing active labels.