Avoid parsing css text if there are identical inline style blocks.

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 10 matching lines @@
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef StyleEngine_h
 #define StyleEngine_h
 
+#include "core/css/StyleSheetContentsCache.h"
 #include "core/dom/Document.h"
 #include "core/dom/DocumentOrderedList.h"
 #include "core/dom/DocumentStyleSheetCollection.h"
 #include "wtf/FastAllocBase.h"
 #include "wtf/ListHashSet.h"
 #include "wtf/RefPtr.h"
 #include "wtf/Vector.h"
+#include "wtf/text/AtomicString.h"
 #include "wtf/text/WTFString.h"
 
 namespace WebCore {
 
 class CSSStyleSheet;
 class Node;
 class RuleFeatureSet;
 class ShadowTreeStyleSheetCollection;
 class StyleSheet;
 class StyleSheetCollection;
@@ skipping 56 matching lines @@
     bool hasScopedStyleSheet() { return m_documentStyleSheetCollection.scopingNodesForStyleScoped(); }
 
     void combineCSSFeatureFlags(const RuleFeatureSet&);
     void resetCSSFeatureFlags(const RuleFeatureSet&);
 
     void didModifySeamlessParentStyleSheet() { m_needsDocumentStyleSheetsUpdate = true; }
     void didRemoveShadowRoot(ShadowRoot*);
     void appendActiveAuthorStyleSheets(StyleResolver*);
     void getActiveAuthorStyleSheets(Vector<const Vector<RefPtr<CSSStyleSheet> >*>& activeAuthorStyleSheets) const;
 
+    StyleSheetContentsCache& styleSheetContentsCache() { return m_styleSheetContentsCache; }
+
 private:
     StyleEngine(Document&);
 
     StyleSheetCollection* ensureStyleSheetCollectionFor(TreeScope&);
     StyleSheetCollection* styleSheetCollectionFor(TreeScope&);
     void activeStyleSheetsUpdatedForInspector();
     bool shouldUpdateShadowTreeStyleSheetCollection(StyleResolverUpdateMode);
 
     typedef ListHashSet<TreeScope*, 16> TreeScopeSet;
     static void insertTreeScopeInDocumentOrder(TreeScopeSet&, TreeScope*);
@@ skipping 24 matching lines @@
     bool m_needsDocumentStyleSheetsUpdate;
 
     String m_preferredStylesheetSetName;
     String m_selectedStylesheetSetName;
 
     bool m_usesSiblingRules;
     bool m_usesSiblingRulesOverride;
     bool m_usesFirstLineRules;
     bool m_usesFirstLetterRules;
     bool m_usesRemUnits;
+
+    StyleSheetContentsCache m_styleSheetContentsCache;
 };
 
 }
 
 #endif