Remove unnecessary includes from dom.

third_party/WebKit/Source/core/dom/StyleEngine.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 21 matching lines @@
 #include "core/css/CSSFontSelectorClient.h"
 #include "core/css/invalidation/StyleInvalidator.h"
 #include "core/css/resolver/StyleResolver.h"
 #include "core/css/resolver/StyleResolverStats.h"
 #include "core/dom/Document.h"
 #include "core/dom/DocumentOrderedList.h"
 #include "core/dom/DocumentStyleSheetCollection.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Allocator.h"
 #include "wtf/ListHashSet.h"
-#include "wtf/RefPtr.h"
 #include "wtf/TemporaryChange.h"
 #include "wtf/Vector.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class CSSFontSelector;
 class CSSStyleSheet;
 class Node;
 class RuleFeatureSet;
@@ skipping 222 matching lines @@
 
     OwnPtr<StyleResolverStats> m_styleResolverStats;
     unsigned m_styleForElementCount = 0;
 
     friend class StyleEngineTest;
 };
 
 } // namespace blink
 
 #endif