stock_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>

        <record id="stock_picking_cancel_form" model="ir.ui.view">
            <field name="name">stock.picking.cancel.form</field>
            <field name="model">stock.picking</field>
            <field name="inherit_id" ref="stock.view_picking_form"/>
            <field name="arch" type="xml">
                <field name="state" position="before">
                    <button name="action_revert_done" string="Reopen"
                        states="done,cancel" type="object" icon="gtk-cancel"
                        confirm="Are you sure you want to reopen this picking?"/>
                </field>
            </field>
        </record>

    </data>
</openerp>