WebGLRenderingContextBase::m_layerCleared is a redundant flag It is flipped after compositing, when the new backbuffer has been cleared.
<rdar://problem/117533757>
Pull request: https://github.com/WebKit/WebKit/pull/19588
Committed 269927@main (0a9d09eaf785): <https://commits.webkit.org/269927@main> Reviewed commits have been landed. Closing PR #19588 and removing active labels.