module Devise::Models::Rememberable

def remember_me!(extend_period=false)

unless remember_across_browsers is true and the user already has a valid token.
Generate a new remember token and save the record without validations 
def remember_me!(extend_period=false)
  self.remember_token = self.class.remember_token if generate_remember_token?
  self.remember_created_at = Time.now.utc if generate_remember_timestamp?(extend_period)
  save(:validate => false)
end