The rest of the Presentation API IDL as stubs.

Source/modules/presentation/Presentation.idl

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// http://webscreens.github.io/presentation-api/#presentation-interface
+// http://webscreens.github.io/presentation-api/#navigatorpresentation
 
 [
     GarbageCollected,
     RuntimeEnabled=Presentation
 ] interface Presentation : EventTarget {
+    readonly attribute PresentationSession? session;
+
+    [CallWith=ScriptState] Promise startSession(DOMString senderId, optional DOMString presentationId = "");

[Peter Beverloo, 2014/10/29 22:21:17]

It looks like the more common way to do this is:

[Default=Undefined] optional DOMString presentationId

[whywhat, 2014/10/29 22:34:06]

Done.

+    [CallWith=ScriptState] Promise joinSession(DOMString senderId, optional DOMString presentationId = "");
+
     attribute EventHandler onavailablechange;
 };