When measuring Safari's button-to-photon latency with html5gamepad.com, I noticed that Safari has roughly double the latency of Chrome for wired USB gamepads (108ms vs 56ms).

I investigated this a bit and found this code in HIDGamepadProvider which I believe accounts for the difference:
https://github.com/WebKit/webkit/blob/950143da027e80924b4bb86defa8a3f21fd3fb1e/Source/WebCore/platform/gamepad/mac/HIDGamepadProvider.cpp#L39

50ms is enormous latency for a gamepad - gaming mice charge a premium in order to deliver ~10ms latency savings.

Could this delay be reduced or eliminated? The rationale around this code isn't entirely clear to me:

    // This isActive check is necessary as we want to delay input notifications from the time of the first input,
    // and not push the notification out on every subsequent input.
    if (!m_inputNotificationTimer.isActive())
        m_inputNotificationTimer.startOneShot(inputNotificationDelay);