project_task_view.xml

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

        <!-- Project Task Form -->
        <record id="project_task_form_view_sla" model="ir.ui.view">
            <field name="name">project_task_form_view_sla</field>
            <field name="model">project.task</field>
            <field name="inherit_id" ref="project.view_task_form2"/>
            <field name="arch" type="xml">

              <page string="Extra Info" position="after">
                <page name="sla_page" string="Service Levels"
                       attrs="{'invisible': [('sla_state', '=', False)]}">
                    <group>
                      <group>
                        <field name="sla_state" />
                      </group>
                      <group>
                        <field name="write_date" />
                      </group>
                    </group>
                    <field name="sla_control_ids" attrs="{'readonly': 1}"/>
                </page>
              </page>

           </field>
        </record>

        <!-- Project Task List  -->
        <record model="ir.ui.view" id="project_task_tree_view_sla">
            <field name="name">project_task_tree_view_slak</field>
            <field name="model">project.task</field>
            <field name="inherit_id" ref="project.view_task_tree2"/>
            <field name="arch" type="xml">

                <field name="project_id" position="after">
                    <field name="sla_state"/>
                </field>

            </field>
        </record>


        <!-- Project Task Filter -->
        <record id="view_project_task_filter_sdesk" model="ir.ui.view">
            <field name="name">
            </field>
            <field name="model">project.task</field>
            <field name="inherit_id" ref="project.view_task_search_form"/>
            <field name="arch" type="xml">

                <filter string="Stage" position="before">
                    <filter string="SLA Status" context="{'group_by':'sla_state'}"/>
                </filter>

           </field>
        </record>

    </data>
</openerp>