Merge pull request #8681 from asutherland/rox-email-perf-fix-2

Bug 846901 - Reduce complexity of clipping in display list. r=asuth(cherry picked from commit 76185af4659982e750bb625f78bd5c81346eefb0)
Merge pull request #8709 from jrburke/bug846901-translatex

Bug 846901: Use a separate card for account listing, instead of nested translateX. r=asuth(cherry picked from commit 3aa6d4023a246cac1f23f088de40d641505f3f0d)
Merge pull request #8713 from asutherland/email-remove-tray-transition-fps-hit

Bug 852550 - [email] naive drawer tray transition from bug 846901 with stationary folder list impacts fps; remove. r=asuth(cherry picked from commit dac742035dea44f4deab98ee333694e2c43c7159)