Presentation API: startSession() no longer takes a presentation id.

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.
 
 // https://w3c.github.io/presentation-api/#interface-presentation
 
 [
     GarbageCollected,
     RuntimeEnabled=Presentation
 ] interface Presentation : EventTarget {
     // This API used by controlling browsing context.
-    // TODO(avayvod): The |presentationId| argument is not in the spec.
-    [CallWith=ScriptState] Promise<PresentationSession> startSession(DOMString url, [Default=Undefined] optional DOMString presentationId);
+    [CallWith=ScriptState] Promise<PresentationSession> startSession(DOMString url);
     // TODO(avayvod): The |presentationId| argument should not be optional.
     [CallWith=ScriptState] Promise<PresentationSession> joinSession(DOMString url, [Default=Undefined] optional DOMString presentationId);
     [CallWith=ScriptState] Promise<PresentationAvailability> getAvailability(DOMString url);
     attribute EventHandler ondefaultsessionstart;
 
     // This API used by presenting browsing context.
     // TODO(avayvod): The spec has |getSession()| and |getSessions()| instead.
     readonly attribute PresentationSession? session;
     // TODO(avayvod): attribute EventHandler onsessionavailable;
 };