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

Source/core/dom/Document.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 607 matching lines @@
 
 void Document::setCompatibilityMode(CompatibilityMode mode)
 {
     if (m_compatibilityModeLocked || mode == m_compatibilityMode)
         return;
     bool wasInQuirksMode = inQuirksMode();
     m_compatibilityMode = mode;
     selectorQueryCache().invalidate();
     if (inQuirksMode() != wasInQuirksMode) {
         // All injected stylesheets have to reparse using the different mode.
+        StyleEngine::clearSheetCache();

[esprehn, 2014/01/09 10:05:32]

You still can't do this, loading any quirks mode document would blow away the
cache for all the non-quirks ones. I'd suggest either having separate caches for
quirks vs non quirks or making the sharing standards mode only for now. I'd
start with standards mode only for now.

[tasak, 2014/01/09 11:59:05]

I see. I agree that it is much better to split cache.
Done.

         m_styleEngine->invalidateInjectedStyleSheetCache();
     }
 }
 
 String Document::compatMode() const
 {
     return inQuirksMode() ? "BackCompat" : "CSS1Compat";
 }
 
 void Document::setDoctype(PassRefPtr<DocumentType> docType)
@@ skipping 4632 matching lines @@
 }
 
 FastTextAutosizer* Document::fastTextAutosizer()
 {
     if (!m_fastTextAutosizer && RuntimeEnabledFeatures::fastTextAutosizingEnabled())
         m_fastTextAutosizer = FastTextAutosizer::create(this);
     return m_fastTextAutosizer.get();
 }
 
 } // namespace WebCore