Include Event.h in fewer header files

Source/modules/mediasource/SourceBuffer.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "modules/mediasource/SourceBuffer.h"
 
 #include "bindings/v8/ExceptionMessages.h"
 #include "bindings/v8/ExceptionState.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/ExecutionContext.h"
+#include "core/events/Event.h"
 #include "core/events/GenericEventQueue.h"
 #include "core/fileapi/FileReaderLoader.h"
 #include "core/fileapi/Stream.h"
 #include "core/html/TimeRanges.h"
 #include "modules/mediasource/MediaSource.h"
 #include "platform/Logging.h"
 #include "platform/TraceEvent.h"
 #include "public/platform/WebSourceBuffer.h"
 #include "wtf/ArrayBuffer.h"
 #include "wtf/ArrayBufferView.h"
@@ skipping 661 matching lines @@
 }
 
 void SourceBuffer::trace(Visitor* visitor)
 {
     visitor->trace(m_source);
     visitor->trace(m_stream);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace WebCore