Mozilla and Chrome do, but disabled by default. Chrome recently tried to enable it and they had to notice that a bunch of crap-devices by bluecoat prevented it

Mozilla and Chrome do, but disabled by default. Chrome recently tried to enable it and they had to notice that a bunch of crap-devices by bluecoat prevented it from working: https://bugs.chromium.org/p/chromium/issues/detail?id=694593 https://bugs.chromium.org/p/chromium/issues/detail?id=694593