Patch forthcoming.
Created attachment 319447 [details] work in progress
Created attachment 319450 [details] the patch
Comment on attachment 319450 [details] the patch seems reasonable r=me
Landed in https://trac.webkit.org/changeset/221434/webkit
<rdar://problem/34694045>
Migrated to https://github.com/gpuweb/WHLSL/issues/210