web/web_sheet_full_width/view/qweb.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
    <data>
        <template id="assets_backend" name="web_sheet_full_width" inherit_id="web.assets_backend">
            <xpath expr="." position="inside">
                <link rel="stylesheet" href="/web_sheet_full_width/static/src/css/web_sheet_full_width.less"/>
            </xpath>
        </template>
    </data>
</openerp>