grep --include="*.css" -rl "address_format" * would be what i would try first but that didn't find anything so i tried.

grep -rl "address_format" * and found it in server/openerp/addons/base/res/res_partner.py

layouts = {
    '%(city)s %(state_code)s\n%(zip)s': """
        <div class="address_format">
            <field name="city" placeholder="City" style="width: 50%%"/>
            <field name="state_id" class="oe_no_button" placeholder="State" style="width: 47%%" options='{"no_open": true}'/>
            <br/>
            <field name="zip" placeholder="ZIP"/>
        </div>
    """,
    '%(zip)s %(city)s': """
        <div class="address_format">
            <field name="zip" placeholder="ZIP" style="width: 40%%"/>
            <field name="city" placeholder="City" style="width: 57%%"/>
            <br/>
            <field name="state_id" class="oe_no_button" placeholder="State" options='{"no_open": true}'/>
        </div>
    """,
    '%(city)s\n%(state_name)s\n%(zip)s': """
        <div class="address_format">
            <field name="city" placeholder="City"/>
            <field name="state_id" class="oe_no_button" placeholder="State" options='{"no_open": true}'/>
            <field name="zip" placeholder="ZIP"/>
        </div>
    """
}