Bug 1605380 - Avoid calculating snapped bounds for some display items twice r=aosmond
Bug 1605380 - Avoid calculating snapped bounds for some display items twice r=aosmond

Differential Revision: https://phabricator.services.mozilla.com/D57976

[wrupdater] From https://hg.mozilla.org/mozilla-central/rev/71e04bcbb142f644dcc49c7ff98a770f3aa0e0ff

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