imported/w3c/web-platform-tests/css/css-color/composited-filters-under-opacity.html Only the overlapping area of the divs is drawn. Link to sample results: https://build.webkit.org/results/GTK-Linux-64-bit-Release-Tests/r269816%20(16989)/imported/w3c/web-platform-tests/css/css-color/composited-filters-under-opacity-diffs.html Its first failure was in the build containing revisions r269569-r269571. Bisecting shows r269570 introduced it.
Fixed by r270040. Expectations updated in r270735. Closing bug.