Remove unused includes from core/accessibility, core/css and core/dom

Source/core/dom/CustomElementRegistry.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
@@ skipping 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef CustomElementRegistry_h
 #define CustomElementRegistry_h
 
 #include "core/dom/ContextLifecycleObserver.h"
 #include "core/dom/CustomElementUpgradeCandidateMap.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/QualifiedName.h"
-#include "wtf/HashSet.h"
 #include "wtf/ListHashSet.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
 #include "wtf/Vector.h"
 #include "wtf/text/AtomicString.h"
 #include "wtf/text/AtomicStringHash.h"
 
 namespace WebCore {
 
@@ skipping 77 matching lines @@
 inline CustomElementRegistry::InstanceSet& CustomElementRegistry::activeCustomElementRegistries()
 {
     DEFINE_STATIC_LOCAL(InstanceSet, activeInstances, ());
     return activeInstances;
 }
 
 
 } // namespace WebCore
 
 #endif