When OES_draw_buffers_indexed is enabled, clearIfComposited must not change color write masks for non-zero draw buffers and it must properly restore the original mask upon completion.
Committed r295485 (251490@main): <https://commits.webkit.org/251490@main> Reviewed commits have been landed. Closing PR #1444 and removing active labels.
<rdar://problem/95004046>