Bug 1659324 - return transparent black when sampling null SWGL texture. r=jimb
Bug 1659324 - return transparent black when sampling null SWGL texture. r=jimb

Differential Revision: https://phabricator.services.mozilla.com/D87190

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/4588aab7372ae20ae1a3cdf4286a198fc240fcbb

servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender