[permissions] Options for "double-keying" permissions (#55)

The Media Capture Task Force is currently discussing the possibility of keying permissions for `getUserMedia` on the combination of the origin of the requesting browsing context as well as the origin of the top-level browsing context.  That is, what you see in the location bar plus the actual requesting origin.  The permissions API doesn't permit additional levels of control like this currently.

I'll note that there are other browsers that key certain permissions on the same tuple of two origins.

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/permissions/issues/55