Update the visibility of XHR-related interfaces to match spec

Source/core/xmlhttprequest/XMLHttpRequest.idl

 /*
  * Copyright (C) 2008, 2011 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
@@ skipping 26 matching lines @@
     "text",
     "legacystream",
 };
 
 // TODO(philipj): Most DOMString types in the XMLHttpRequest interface should be
 // either ByteString or USVString.
 [
     ActiveDOMObject,
     Constructor,
     ConstructorCallWith=ScriptState,
-    // TODO(philipj): The spec has Exposed=(Window,Worker)
-    // https://github.com/whatwg/xhr/issues/19
     Exposed=(Window,DedicatedWorker,SharedWorker)
 ] interface XMLHttpRequest : XMLHttpRequestEventTarget {
     // event handler
     attribute EventHandler onreadystatechange;
 
     // states
     const unsigned short UNSENT = 0;
     const unsigned short OPENED = 1;
     const unsigned short HEADERS_RECEIVED = 2;
     const unsigned short LOADING = 3;
@@ skipping 18 matching lines @@
     readonly attribute DOMString statusText;
     DOMString? getResponseHeader(DOMString name);
     DOMString getAllResponseHeaders();
     [RaisesException] void overrideMimeType(DOMString mime);
     [RaisesException=Setter] attribute XMLHttpRequestResponseType responseType;
     [Custom=Getter, RaisesException=Getter] readonly attribute any response;
     [Custom=Getter, RaisesException=Getter] readonly attribute DOMString responseText;
     // TODO(philipj): responseXML should be [Exposed=Window].
     [RaisesException=Getter] readonly attribute Document? responseXML;
 };