def ng_root_selector(root_selector = nil)
    opt = ng.page.ng_session_options
    if root_selector
      opt[:root_selector] = root_selector
    end
    opt[:root_selector] || ::Angular.root_selector
  end
def ng_root_selector(root_selector = nil)
    opt = ng.page.ng_session_options
    if root_selector
      opt[:root_selector] = root_selector
    end
    opt[:root_selector] || ::Angular.root_selector
  end
Get or set selector to find ng-app for current capybara test session

 TIP: try using '[ng-app]', which will find ng-app as attribute anywhere.

 @param root_selector if nil then return current value without change
 @return test specific selector to find ng-app,
 by default global ::Angular.root_selector is used.