sale_mrp_link/views/mrp_production.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
  <data>
      <record id="act_so_2_mo" model="ir.actions.act_window">
          <field name="name">Production</field>
          <field name="res_model">mrp.production</field>
          <field name="view_type">form</field>
          <field name="view_mode">tree,form,graph</field>
          <field name="context">{'search_default_sale_order_id': active_id}</field>
      </record>

      <record id="sale_order_form_buttons" model="ir.ui.view">
          <field name="name">sale.order.form.buttons</field>
          <field name="model">sale.order</field>
          <field name="inherit_id" ref="sale.view_order_form"/>
          <field name="priority" eval="30"/>
          <field name="arch" type="xml">
              <xpath expr="//h1" position="attributes">
                  <attribute name="class">oe_left</attribute>
              </xpath>
              <xpath expr="//h1" position="after">
                  <div class="oe_right oe_button_box" name="buttons">
                      <button class="oe_inline oe_stat_button" type="action"
                              name="%(act_so_2_mo)d"
                              attrs="{'invisible': [('production_count', '=', 0)]}"
                              icon="fa-gears">
                          <field string="Production" name="production_count" widget="statinfo"/>
                      </button>
                  </div>
              </xpath>
          </field>
      </record>

      <record id="mrp_production_sale_info_search_view" model="ir.ui.view">
          <field name="name">mrp.production.sale.info.search</field>
          <field name="model">mrp.production</field>
          <field name="inherit_id" ref="mrp.view_mrp_production_filter"/>
          <field name="arch" type="xml">
              <field name="product_id" position="after">
                  <field name="partner_id" string="Customer"/>
                  <field name="sale_order_id" string="Sale Order"/>
              </field>
              <filter string="Product" position="before">
                  <filter string="Customer" icon="terp-accessories-archiver"
                          domain="[]" context="{'group_by':'partner_id'}"/>
                  <filter string="Sale Order" icon="terp-accessories-archiver"
                          domain="[]" context="{'group_by':'sale_order_id'}"/>
              </filter>
          </field>
      </record>

  </data>
</openerp>