Earlier quoted context omitted.
This is implemented. It works for me in chrome
You're right, thank you. At least it works on chrome on osx. It didn't work when I tested it earlier in dev channel chrome on windows.
It works on OSX because it appears the operating system automatically creates a keypress of scancode 27 (escape) when you press "^[".
The special code in term_keypress_inner to handle this combination of keys is never hit, because no keypress event is created for ^[, but it isn't necessary on OSX due to the above feature.
You could expand your handling of keyup/keydown to handle it. For example, change your keyup handler to the following:
$(document).keyup(function(e) { if(e.keyCode === 27 || (e.ctrlKey && e.keyCode === 219)) { do_escape(); } });