Add promise type to EME idl files

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 21 matching lines @@
     // 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 generateRequest(DOMString initDataType, ArrayBuffer initData);
-    [CallWith=ScriptState] Promise generateRequest(DOMString initDataType, ArrayBufferView initData);
-    [CallWith=ScriptState] Promise load(DOMString sessionId);
+    [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 update(ArrayBuffer response);
-    [CallWith=ScriptState] Promise update(ArrayBufferView response);
-    [CallWith=ScriptState] Promise close();
-    [CallWith=ScriptState] Promise remove();
+    [CallWith=ScriptState] Promise<void> update(ArrayBuffer response);
+    [CallWith=ScriptState] Promise<void> update(ArrayBufferView response);
+    [CallWith=ScriptState] Promise<void> close();
+    [CallWith=ScriptState] Promise<void> remove();
 };