social/base_search_mail_content/views/trgm_index_view.xml

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

        <record model="ir.ui.view" id="trgm_index_view_form">
            <field name="name">trgm.index.view.form</field>
            <field name="model">trgm.index</field>
            <field name="inherit_id" ref="base_search_fuzzy.trgm_index_view_form"/>
            <field name="arch" type="xml">
                <field name="field_id" position="attributes">
                    <attribute name="domain">[('ttype', 'in', ['char', 'text', 'html'])]</attribute>
              </field>
          </field>
        </record>

    </data>
</openerp>