Remove unnecessary includes from dom.

third_party/WebKit/Source/core/dom/StyleSheetCollection.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 13 matching lines @@
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef StyleSheetCollection_h
 #define StyleSheetCollection_h
 
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Allocator.h"
-#include "wtf/RefPtr.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class CSSStyleSheet;
 class StyleSheet;
 
 class CORE_EXPORT StyleSheetCollection : public GarbageCollected<StyleSheetCollection> {
     WTF_MAKE_NONCOPYABLE(StyleSheetCollection);
 public:
@@ skipping 13 matching lines @@
     DECLARE_VIRTUAL_TRACE();
 
 protected:
     HeapVector<Member<StyleSheet>> m_styleSheetsForStyleSheetList;
     HeapVector<Member<CSSStyleSheet>> m_activeAuthorStyleSheets;
 };
 
 } // namespace blink
 
 #endif // StyleSheetCollection_h