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

Source/core/dom/StyleEngine.cpp

 /*
  * 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, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 446 matching lines @@
     for (TreeScopeSet::iterator it = begin; it != end; ++it) {
         if (StyleSheetCollection* collection = m_styleSheetCollectionMap.get(*it)) {
             styleResolver->setBuildScopedStyleTreeInDocumentOrder(!collection->scopingNodesForStyleScoped());
             styleResolver->appendAuthorStyleSheets(0, collection->activeAuthorStyleSheets());
         }
     }
     styleResolver->finishAppendAuthorStyleSheets();
     styleResolver->setBuildScopedStyleTreeInDocumentOrder(false);
 }
 
+StyleSheetContents* StyleEngine::findStyleSheetContents(const AtomicString& sheetText)
+{
+    return m_styleSheetContentsCache.find(sheetText);
 }
+
+void StyleEngine::registerStyleSheetContents(const AtomicString& sheetText, StyleSheetContents* contents)
+{
+    m_styleSheetContentsCache.add(sheetText, contents);
+}
+
+void StyleEngine::unregisterStyleSheetContents(const AtomicString& sheetText)
+{
+    m_styleSheetContentsCache.remove(sheetText);
+}
+
+}