Comply (more) with check-webkit-style in and around HTMLMediaElement

Source/core/html/track/vtt/VTTElement.h

Index: Source/core/html/track/vtt/VTTElement.h
diff --git a/Source/core/html/track/vtt/VTTElement.h b/Source/core/html/track/vtt/VTTElement.h
index 287f3f63e53805207225a4df410ad699759de3e0..8e58ca6b83ef96c3bbfe84b358751acbc6b9ac43 100644
--- a/Source/core/html/track/vtt/VTTElement.h
+++ b/Source/core/html/track/vtt/VTTElement.h
@@ -23,6 +23,9 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#ifndef VTTElement_h
+#define VTTElement_h
+
 #include "core/html/HTMLElement.h"
 
 namespace blink {
@@ -83,3 +86,4 @@ DEFINE_ELEMENT_TYPE_CASTS(VTTElement, isVTTElement());
 
 } // namespace blink
 
+#endif // VTTElement_h