Bug 1614655 - Part 1: Remove item_key from CommonItemProperties r=jrmuizel
Bug 1614655 - Part 1: Remove item_key from CommonItemProperties r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D66442

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/10897d6106a85383569ac03d8d14907a4c063d9b

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