Open these WPT test in WebKit and compare the rendering of the backdrop filter with the expected pages which use the css filter. Or compare the rendering with the backdrop filter rendering in other browsers. imported/w3c/web-platform-tests/css/filter-effects/backdrop-filters-grayscale-001.html imported/w3c/web-platform-tests/css/filter-effects/backdrop-filters-sepia.html
<rdar://problem/127322912>