function getNormalizedEventCoords(evt, pageOffset, clientRect) {
    if (!evt) {
        return { x: 0, y: 0 };
    }
    var x = pageOffset.x, y = pageOffset.y;
    var documentX = x + clientRect.left;
    var documentY = y + clientRect.top;
    var normalizedX;
    var normalizedY;
    // Determine touch point relative to the ripple container.
    if (evt.type === 'touchstart') {
        var touchEvent = evt;
        normalizedX = touchEvent.changedTouches[0].pageX - documentX;
        normalizedY = touchEvent.changedTouches[0].pageY - documentY;
    }
    else {
        var mouseEvent = evt;
        normalizedX = mouseEvent.pageX - documentX;
        normalizedY = mouseEvent.pageY - documentY;
    }
    return { x: normalizedX, y: normalizedY };
}
Stores result from supportsCssVariables to avoid redundant processing to
detect CSS custom variable support.