Use event init dictionaries in core/{css,html}

Source/core/html/MediaKeyEvent.h

 /*
  * Copyright (C) 2012 Google 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.
  */
 
 #ifndef MediaKeyEvent_h
 #define MediaKeyEvent_h
 
 #include "core/dom/DOMTypedArray.h"
 #include "core/events/Event.h"
 #include "core/html/MediaKeyError.h"
+#include "core/html/MediaKeyEventInit.h"
 
 namespace blink {
 
-struct MediaKeyEventInit : public EventInit {
-    MediaKeyEventInit();
-
-    String keySystem;
-    String sessionId;
-    RefPtr<DOMUint8Array> initData;
-    RefPtr<DOMUint8Array> message;
-    String defaultURL;
-    RefPtrWillBeMember<MediaKeyError> errorCode;
-    unsigned short systemCode;
-};
-
 class MediaKeyEvent final : public Event {
     DEFINE_WRAPPERTYPEINFO();
 public:
     virtual ~MediaKeyEvent();
 
     static PassRefPtrWillBeRawPtr<MediaKeyEvent> create()
     {
         return adoptRefWillBeNoop(new MediaKeyEvent);
     }
 
@@ skipping 23 matching lines @@
     RefPtr<DOMUint8Array> m_initData;
     RefPtr<DOMUint8Array> m_message;
     String m_defaultURL;
     RefPtrWillBeMember<MediaKeyError> m_errorCode;
     unsigned short m_systemCode;
 };
 
 } // namespace blink
 
 #endif // MediaKeyEvent_h