Use case: iframe pop out

[yoavweiss]

In WICG/proposals#289 (comment) @jakearchibald points out that an iframe "pop out" is a related use case, and it'd be good to support it as well.

We should think about how it can be tackled and if that use case can be an extension/enhancement of this API proposal.

[jakearchibald]

Yeah, this being a later extension seems fine to me.

[dotproto]

The use-cases are for things like "popping out" the chat window or media player.

From @jakearchibald's comment in WICG/proposals#289

Another case is email webapps where you can move a message composition from the main UI to a separate window. In both cases you may also want to move the popped-out window back into the main frame.