Remove obsolete ready and error events from MediaKeySession.

Source/modules/encryptedmedia/MediaKeySession.idl

 /*
  * Copyright (C) 2013 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 11 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 [
     ActiveDOMObject,
     RuntimeEnabled=EncryptedMedia,
     GarbageCollected,
     TypeChecking=Interface
 ] interface MediaKeySession : EventTarget {
-    // error state
-    readonly attribute MediaKeyError error;
-
     // session properties
-    readonly attribute DOMString keySystem;
     readonly attribute DOMString sessionId;
     readonly attribute unrestricted double expiration;
     [CallWith=ScriptState] readonly attribute Promise closed;
 
     // session initialization
     [CallWith=ScriptState] Promise<void> generateRequest(DOMString initDataType, ArrayBuffer initData);
     [CallWith=ScriptState] Promise<void> generateRequest(DOMString initDataType, ArrayBufferView initData);
     [CallWith=ScriptState] Promise<boolean> load(DOMString sessionId);
 
     // session operations
     [CallWith=ScriptState] Promise<void> update(ArrayBuffer response);
     [CallWith=ScriptState] Promise<void> update(ArrayBufferView response);
     [CallWith=ScriptState] Promise<void> close();
     [CallWith=ScriptState] Promise<void> remove();
 };