Backed out changeset 95324d36ded5 (Bug 1518405) for causing performance regressions.

commit7adb490485eff0783071a3e132005bceeb337461
parent1b2c69a5c17254393a51a095ab61ca4674a9c3d1
hg340d5146c4052a47c5aa4f70817dc3ee9fd4e7da
git7adb490485eff0783071a3e132005bceeb337461
authorMatt Woodrow <mwoodrow@mozilla.com>
committerMatt Woodrow <mwoodrow@mozilla.com>
commit timeFri, 11 Jan 2019 18:59:46 +1300