Expand arrow gone from summary element

Created by: vanillajonathan

The visual expand arrow visible in Chrome and Firefox on the details element disappears with normalize.

I don't know if this is intentional or not.

<details>
  <summary>Click on this summary to expand</summary>
  <p>Here is additional text, visible when expanded...</p>
</details> 

Bootstrap 3.3.7 https://jsfiddle.net/vu6o29es/

Cross-reference: necolas/normalize.css#640