Bug 1664735 - micro-optimizations for WR sample_gradient. r=mattwoodrow
Bug 1664735 - micro-optimizations for WR sample_gradient. r=mattwoodrow

Differential Revision: https://phabricator.services.mozilla.com/D90054

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/b9ca78d0a835ee9432d00637a96b3067b5d799dd

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