There was a known problem with video performance with e10s, though it was fixed two months ago (now Firefox 45 Dev Edition). The e10s sandbox inadvertently blocked hardware video decoding.<p><a href="https:&#x2F;&#x2F;bugzilla.mozilla.org&#x2F;show_bug.cgi?id=1217185" rel="nofollow">https:&#x2F;&#x2F;bugzilla.mozilla.org&#x2F;show_bug.cgi?id=1217185</a>