https://github.com/web-platform-tests/wpt/blob/4f26de067e0a83751bf0102f3a944ebb492b095b/html/canvas/element/pixel-manipulation/2d.imageData.object.ctor.basics.html#L72 Currently WebKit probably returns the right thing but fails the tests. See the discussion in https://bugs.webkit.org/show_bug.cgi?id=250543