This is a request for WebKit's position on extending getDisplayMedia to
also accept DisplayMediaStreamConstraints.surfaceSwitching.
The PR that introduced this behavior to the getDisplayMedia spec was
approved by Apple engineer Youenn Fablet.

Links:
* Explainer: https://docs.google.com/document/d/1kqdLoUcwWe8znVCMXyz2FHk9WMylHbIo7gUjhyHmY_w/edit?usp=sharing
* Spec: https://github.com/w3c/mediacapture-screen-share/pull/225/files
* ChromeStatus entry: https://chromestatus.com/feature/5067650299330560