sale_order_line_view/views/res_partner.xml

<?xml version="1.0"?>
<openerp>
    <data>
       <record id="action_sale_order_line_tree" model="ir.actions.act_window">
            <field name="name">Sale order lines</field>
            <field name="res_model">sale.order.line</field>
            <field name="view_type">form</field>
            <field name="view_mode">tree,form</field>
            <field name="domain">[('order_partner_id', '=', active_id)]</field>
            <field name="context">{'search_default_partner_id': active_id}</field>
        </record>

        <record id="res_partner_order_line_button_form" model="ir.ui.view">
            <field name="name">res.partner.order.line.button.form</field>
            <field name="model">res.partner</field>
            <field name="inherit_id" ref="base.view_partner_form" />
            <field name="arch" type="xml">
                <xpath expr="//div[@name='buttons']" position="inside">
                    <button class="oe_inline oe_stat_button" type="action"
                        icon="fa-align-justify"
                        attrs="{'invisible': [('customer', '=', False)]}"
                        name="%(sale_order_line_view.action_sale_order_line_tree)d">
                        <field string="Sale order lines" name="lines_count" widget="statinfo"/>
                    </button>
                 </xpath>
            </field>
        </record>
    </data>
</openerp>