pos_stock_quantity/views/header.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <template id="assets_backend" inherit_id="web.assets_backend" name="pos_stock_quantity assets">
            <xpath expr="." position="inside">
                <script type="text/javascript" src="/pos_stock_quantity/static/src/js/pos_stock.js"></script>
                <script type="text/javascript" src="/pos_stock_quantity/static/src/js/popup.js"></script>
                <script type="text/javascript" src="/pos_stock_quantity/static/src/js/main.js"></script>
            </xpath>
        </template>

        <template id="pos_css" inherit_id="point_of_sale.index">
            <xpath expr="//head" position="inside">
                <link rel="stylesheet" href="/pos_stock_quantity/static/src/css/stock_qty.css"/>
            </xpath>
        </template>
    </data>
</openerp>