Define whether multiple simultaneous calls are permitted to startSession()

[markafoltz]

mfoltz@google.com:
Are multiple simultaneous calls permitted to startSession()? My intuition is "no", but I would like to ask the group if there are any use cases where this is necessary. If the answer is "yes" it adds some constraints and complexity to the user interface for screen selection in the browser. In particular if we return a Promise from startSession() then I am not sure how we would enforce one-at-a-time.

[markafoltz]

The current spec reads:

While there is a pending call to startSession asking the user to select a screen (that the user has not yet accepted or canceled), the browser may choose to reject subsequent calls to startSession from the same page, by returning a Promise that never resolves. This will prevent the browser from needing to 'queue up' requests to present to the user.

It seems more logical to have all pending Promises resolve or reject identically.