launch persona in browser

launch_persona.py

from marionette import Marionette
from gaiatest.apps.browser.app import Browser
m = Marionette('localhost', 2828)
m.start_session()
browser = Browser(m)
browser.launch()
browser.go_to_url('http://native.123done.org\n')
browser.switch_to_content()
#wait
btn = m.find_element('css selector', 'img[src*="persona-login"]')
btn.click()

m.switch_to_frame()
n_ui = m.find_element('css selector', 'iframe[src*="firefoxos.persona.org/sign_in"]')
m.switch_to_frame(n_ui)
pp = m.find_element('link text', 'Privacy Policy')
pp.is_displayed()

# returns False, but it's I can see it on the phone
# I can't click on it or other controls, most everything is is_displayed = False