can't scroll in the embedded demo page of iron-collapse (ios 10.1.1)

Description

can't scroll in the embedded demo page of iron-collapse after expanding the content.

Expected outcome

You can scroll to see all content.

Actual outcome

No Scrolling possible.

Live Demo

https://beta.webcomponents.org/element/PolymerElements/iron-collapse/demo/demo/index.html

Steps to reproduce

1. Use an iPhone
2. Go to the demo page of the iron-collapse. The content must not use all of the screen (use link above)
3. Toggle the iron-collapse the get all the content. The content must use all of the screen
4. Try to scroll

Browsers Affected

• [ ] Chrome
• [ ] Firefox
• [x] Safari for iOS
• [ ] Safari 9
• [ ] Safari 8
• [ ] Safari 7
• [ ] Edge
• [ ] IE 11
• [ ] IE 10