Define lifetime of the presented document; when can the user agent close the document

[mfoltzgoogle]

Presumably the user agent will provide the ability for the browser with the initiating page to close the presented document (local or remote). However we may want the user agent to close it on the user's behalf when:

(1) There are no controlling sessions connected for some period of time (e.g., idle timeout)
(2) The presentation is being rendered locally (1-UA) and the media stream has has been terminated permanently.
(3) The presentation is being rendered locally and the user wishes to exit the user-agent.
(4) The presentation wishes to terminate itself.

Some of these scenarios can be implemented by the app developer; if so the behavior of e.g. window.close() should be defined in the presentation context.

[mfoltzgoogle]

I am incorporating my comment into #35 and closing this.