PresentationConnection.url should be optional?

[markafoltz]

The algorithm steps for creating a PresentationConnection set the url attribute after construction. It seems like we should make the attribute optional (like id) since it is not set in the constructor.

[markafoltz]

Three algorithms that create PresentationConnection objects and set attributes after construction:

• https://w3c.github.io/presentation-api/#starting-a-presentation
• https://w3c.github.io/presentation-api/#reconnecting-to-a-presentation
• https://w3c.github.io/presentation-api/#monitoring-incoming-presentation-connections

Alternatively, we could define a constructor that takes the url and id and modify the algorithms to use that; which seems better, since the API is not intended is to expose PresentationConnections without these properties set.

[markafoltz]

Reviewing the spec, in all cases where the user agent instantiates a PresentationConnection, it sets both the URL and the ID before returning it to the caller. So it makes more sense to make both PresentationConnection.id and PresentationConnection.url mandatory.