Why ion-option-button dosen't work?

i’m using ion-list in my app. But i found that ion-option-button dosen’t work, nothing happened when i add ion-option-button to ion-list. I check out the demo and it doesn’t work either.
the demo address is http://ionicframework.com/docs/api/directive/ionList/.there are two ion-option-button in the demo, called edit and share. neither of them is shown.
Also i tested my app on android-x86 vm and got the same result.

found it. you must pull the item to left ,then you can see the option buttons.