Bug 1679482 - Don't compute external surface dependencies when not using the Draw compositor. r=gw
Bug 1679482 - Don't compute external surface dependencies when not using the Draw compositor. r=gw

Differential Revision: https://phabricator.services.mozilla.com/D98272

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/41fc102c92a332aa20dfa6c6591a24cc2295bd36

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