[PresentationAPI] on-session-message handler for binary messages (Blink side).

Source/modules/presentation/PresentationSession.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/#presentationsession
 
 enum PresentationSessionState {
     "connected",
     "disconnected"
 };
 
 [
     GarbageCollected,
     RuntimeEnabled=Presentation
 ] interface PresentationSession : EventTarget {
     readonly attribute DOMString? id;
     readonly attribute PresentationSessionState state;
 
     [RaisesException] void send(DOMString message);
     [RaisesException] void send(ArrayBuffer data);
     [RaisesException] void send(ArrayBufferView data);
     [RaisesException] void send(Blob data);
     void close();
 
+    attribute BinaryType binaryType;

[USE s.singapati at gmail.com, 2015/06/30 14:32:29]

"enum BinaryType" is already defined in WebSocket.idl, so defining again here
causes the build failure (Exception: Enumeration BinaryType has multiple
definitions). Otherwise, defining binaryType for eg., as DOMString is needed to
avoid dependency from WebSocket.idl.

     attribute EventHandler onmessage;
     attribute EventHandler onstatechange;
 };