The normal module to update CCS does not work as it's changing the entire web backend css instead, not just im_chat_printx.css changes. Any ideas what is wrong below? 

__openerp__.py

'depends' : ['im_chat'],
'init_xml' : [],
'demo_xml' : [],
'update_xml' : [],
'data' : ['views/im_chat_printx.xml'],
'installable': True,
'active': True,
'description': """
New Live Chat CSS.
    """,
}

im_chat_printx.xml

<openerp>
    <data>
        <template id="assets_backend" name="im_chat_printx assets" inherit_id="web.assets_backend">
            <xpath expr="." position="inside">
                <link rel="stylesheet" href="/im_chat_printx/static/src/css/im_chat_printx.css"/>
            </xpath>
        </template>
    </data>
</openerp>