ir_attachment_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record id="ir_attachment_dropbox_form_view" model="ir.ui.view">
            <field name="name">ir.attachment.dropbox.form</field>
            <field name="model">ir.attachment</field>
            <field name="type">form</field>
            <field name="inherit_id" ref="base.view_attachment_form"/>
            <field name="arch" type="xml">
                <xpath expr="/form/notebook/page[@string='Attachment']/group[1]" position="replace">
                    <group col="4" colspan="4">
                        <separator string="Data" colspan="4"/>
                        <newline />
                        <group col="2" colspan="4" attrs="{'invisible':[('type','!=','binary')]}">
                            <field name="datas" filename="datas_fname"/>
                            <field name="datas_fname" select="1"/>
                        </group>
                        <group col="2" colspan="4" attrs="{'invisible':[('type','!=','url')]}">
                            <field name="url" widget="url"/>
                        </group>
                        <group col="4" colspan="4" attrs="{'invisible': [('type','!=','dropbox')]}">
                            <group colspan="4" col="4">
                                <field name="dropbox_path" colspan="4"/>
                                <field name="dropbox_rev" invisible="1"/>
                            </group>
                            <group colspan="4" col="4">
                                <button name="%(action_wizard_dropbox_ir_attach)d" type="action"
                                 colspan="2" string="Select File"/>
                                <button name="%(action_wizard_dropbox_download_file)d" type="action"
                                    colspan="2" string="Download File"/>
                            </group>
                        </group>
                    </group>
                </xpath>
            </field>
        </record>
    </data>
</openerp>