web/web_listview_number_right/views/asset.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <template id="assets_backend" name="web_number_right assets" inherit_id="web.assets_backend">
            <xpath expr="." position="inside">
                 <link rel="stylesheet" type="text/less" href="/web_listview_number_right/static/src/less/list_view.less"/>
            </xpath>
        </template>
    </data>
</openerp>