class Capybara::RSpecMatchers::BecomeClosed

def matches?(window)
  @window = window
  @wait_time = Capybara::Queries::BaseQuery.wait(@options, window.session.config.default_max_wait_time)
  start_time = Capybara::Helpers.monotonic_time
  while window.exists?
    return false if (Capybara::Helpers.monotonic_time - start_time) > @wait_time
    sleep 0.05
  end
  true
end