Hello maintainers,

Pointerup events ceased to be detected on desktop Safari and on Chrome 49 (with more versions probably affected) once I deleted the following code on the faith that I would not be needing it:

    // Support: Firefox <=44 only
    // FF Ubuntu includes the lifted button in the `buttons` property on
    // mouseup.
    // https://bugzilla.mozilla.org/show_bug.cgi?id=1223366
    e.buttons &= ~BUTTON_TO_BUTTONS[e.button];
    if (e.buttons === 0) {
      dispatcher.up(e);
    } else {
      dispatcher.move(e);
    }

I have a hunch this may be the root cause of issue #352.
Crude test case below, with the whole of pep.js as an inline script and the aforementioned snippet commented out.
Thanks.

bug.txt