mail-addons/mail_archives/views/templates.xml

<?xml version="1.0"?>
<openerp>
    <data>
        <template id="res_partner_mails_count_assets_backend"
                  name="res_partner_mails_count_assets_backend"
                  inherit_id="web.assets_backend">
            <xpath expr="." position="inside">
                <script src="/mail_archives/static/src/js/archives.js" type="text/javascript"></script>
            </xpath>
        </template>
    </data>
</openerp>