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

Source/core/css/StyleSheetContents.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 49 matching lines @@
 
     const CSSParserContext& parserContext() const { return m_parserContext; }
 
     const AtomicString& determineNamespace(const AtomicString& prefix);
 
     void parseAuthorStyleSheet(const CSSStyleSheetResource*, const SecurityOrigin*);
     bool parseString(const String&);
     bool parseStringAtPosition(const String&, const TextPosition&, bool);
 
     bool isCacheable() const;
+    bool maybeCacheable() const;
 
     bool isLoading() const;
 
+    void checkLoadedFor(PassRefPtr<Node>);
     void checkLoaded();
     void startLoadingDynamicSheet();
 
     StyleSheetContents* rootStyleSheet() const;
     bool hasSingleOwnerNode() const;
     Node* singleOwnerNode() const;
     Document* singleOwnerDocument() const;
 
     const String& charset() const { return m_parserContext.charset; }
 
     bool loadCompleted() const { return m_loadCompleted; }
     bool hasFailedOrCanceledSubresources() const;
 
     KURL completeURL(const String& url) const;
     void addSubresourceStyleURLs(ListHashSet<KURL>&);
 
-    void setHasSyntacticallyValidCSSHeader(bool b) { m_hasSyntacticallyValidCSSHeader = b; }
+    void setHasSyntacticallyValidCSSHeader(bool isValidCss);
     bool hasSyntacticallyValidCSSHeader() const { return m_hasSyntacticallyValidCSSHeader; }
 
     void parserAddNamespace(const AtomicString& prefix, const AtomicString& uri);
     void parserAppendRule(PassRefPtr<StyleRuleBase>);
     void parserSetEncodingFromCharsetRule(const String& encoding);
     void parserSetUsesRemUnits(bool b) { m_usesRemUnits = b; }
 
     void clearRules();
 
     bool hasCharsetRule() const { return !m_encodingFromCharsetRule.isNull(); }
@@ skipping 24 matching lines @@
     bool wrapperInsertRule(PassRefPtr<StyleRuleBase>, unsigned index);
     void wrapperDeleteRule(unsigned index);
 
     PassRefPtr<StyleSheetContents> copy() const { return adoptRef(new StyleSheetContents(*this)); }
 
     void registerClient(CSSStyleSheet*);
     void unregisterClient(CSSStyleSheet*);
     bool hasOneClient() { return m_clients.size() == 1; }
 
     bool isMutable() const { return m_isMutable; }
-    void setMutable() { m_isMutable = true; }
+    void setMutable();
 
     bool isInMemoryCache() const { return m_isInMemoryCache; }
     void addedToMemoryCache();
     void removedFromMemoryCache();
 
     void shrinkToFit();
 
 private:
     StyleSheetContents(StyleRuleImport* ownerRule, const String& originalURL, const CSSParserContext&);
     StyleSheetContents(const StyleSheetContents&);
 
     void clearCharsetRule();
+    void clearCache();
 
     StyleRuleImport* m_ownerRule;
 
     String m_originalURL;
 
     String m_encodingFromCharsetRule;
     Vector<RefPtr<StyleRuleImport> > m_importRules;
     Vector<RefPtr<StyleRuleBase> > m_childRules;
     typedef HashMap<AtomicString, AtomicString> PrefixNamespaceURIMap;
     PrefixNamespaceURIMap m_namespaces;
 
     bool m_loadCompleted : 1;
     bool m_hasSyntacticallyValidCSSHeader : 1;
     bool m_didLoadErrorOccur : 1;
     bool m_usesRemUnits : 1;
     bool m_isMutable : 1;
     bool m_isInMemoryCache : 1;
 
     CSSParserContext m_parserContext;
 
     Vector<CSSStyleSheet*> m_clients;
 };
 
 } // namespace
 
 #endif