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 157 matching lines @@
 
     void didAttach();
     void didDetach();
     bool shouldClearResolver() const;
     StyleResolverChange resolverChanged(RecalcStyleTime, StyleResolverUpdateMode);
     unsigned resolverAccessCount() const;
 
     void collectDocumentActiveStyleSheets(StyleSheetCollectionBase&);
     void markDocumentDirty();
 
+    static PassRefPtr<CSSStyleSheet> createSheet(Element*, const String& text, TextPosition startPosition, bool createdByParser);
+    static void removeSheet(StyleSheetContents*);
+
 private:
     StyleEngine(Document&);
 
     StyleSheetCollection* ensureStyleSheetCollectionFor(TreeScope&);
     StyleSheetCollection* styleSheetCollectionFor(TreeScope&);
     bool shouldUpdateShadowTreeStyleSheetCollection(StyleResolverUpdateMode);
     void resolverThrowawayTimerFired(Timer<StyleEngine>*);
 
     void markTreeScopeDirty(TreeScope&);
 
     bool isMaster() const { return m_isMaster; }
     Document* master();
 
     typedef ListHashSet<TreeScope*, 16> TreeScopeSet;
     static void insertTreeScopeInDocumentOrder(TreeScopeSet&, TreeScope*);
     void clearMediaQueryRuleSetOnTreeScopeStyleSheets(TreeScopeSet treeScopes);
 
     void createResolver();
 
     void notifyPendingStyleSheetAdded();
     void notifyPendingStyleSheetRemoved(RemovePendingSheetNotificationType);
 
+    static PassRefPtr<CSSStyleSheet> parseSheet(Element*, const String& text, TextPosition startPosition, bool createdByParser);
+
     Document& m_document;
     bool m_isMaster;
 
     // Track the number of currently loading top-level stylesheets needed for rendering.
     // Sheets loaded using the @import directive are not included in this count.
     // We use this count of pending sheets to detect when we can begin attaching
     // elements and when it is safe to execute scripts.
     int m_pendingStylesheets;
 
     mutable Vector<RefPtr<CSSStyleSheet> > m_injectedAuthorStyleSheets;
@@ skipping 25 matching lines @@
     unsigned m_lastResolverAccessCount;
     Timer<StyleEngine> m_resolverThrowawayTimer;
     OwnPtr<StyleResolver> m_resolver;
 
     RefPtr<CSSFontSelector> m_fontSelector;
 };
 
 }
 
 #endif