Depends on D19755

Differential Revision: https://phabricator.services.mozilla.com/D19757

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1398095
gecko-commit: b8393b9641e543cd482526dfbaa81cb673d39d6f
gecko-integration-branch: central
gecko-reviewers: ato