Sync the XHR-related interfaces with the spec

Source/core/events/ProgressEvent.idl

 /*
  * Copyright (C) 2007 Apple Inc. All rights reserved.
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  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
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  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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-// http://www.w3.org/TR/progress-events/#interface-progressevent
+// https://xhr.spec.whatwg.org/#interface-progressevent
 
+// TODO(philipj): The spec has Exposed=(Window,Worker)
+// https://github.com/whatwg/xhr/issues/19
 [
     Constructor(DOMString type, optional ProgressEventInit eventInitDict),
 ] interface ProgressEvent : Event {
     readonly attribute boolean lengthComputable;
     readonly attribute unsigned long long loaded;
     readonly attribute unsigned long long total;
 };
-