In connection with linking to this spec from the getusermedia spec, I need a reference for "request permission". This should be a procedure, not an API call (although I suppose the API call should just say "invoke the procedure").

Suggested content:

• Query for the permission
• if permission is "granted", return "granted"
• if permission is "denied", return "denied"
• if permission is "prompt" or does not exist, prompt the user in a browser-specific fashion, and return a value based on the user's decision. If the user never decides, do not return. (Yes, we found it necessary to write this explicitly in the getusermedia spec.)

Text that can be copied is in the getUserMedia section of the getusermedia spec.

@jyasskin, can you extract your commit fixing this to a separate pull request?