odoo_top_trending_products/views/purchase_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record id="view_purchase_order_filter_top25_product" model="ir.ui.view">
            <field name="name">purchase.order.filter</field>
            <field name="model">purchase.order</field>
            <field name="inherit_id" ref="purchase.view_purchase_order_filter"/>
            <field name="arch" type="xml">
                <xpath expr="//search" position="inside">
                    <filter string="Top productos de mayor tendencia" domain="[('id','!=',False)]" context="{'top_25': True}"/>
                </xpath>
            </field>
        </record>
    </data>
</openerp>