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

Source/core/css/StyleSheetContentsCache.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Google 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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * 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 MatchedPropertiesCache_h
-#define MatchedPropertiesCache_h
+#ifndef StyleSheetContentsCache_h
+#define StyleSheetContentsCache_h
 
-#include "core/css/resolver/MatchResult.h"
-
+#include "core/css/StyleSheetContents.h"
 #include "platform/Timer.h"
 #include "wtf/Forward.h"
 #include "wtf/HashMap.h"
 #include "wtf/Noncopyable.h"
+#include "wtf/RefPtr.h"
+#include "wtf/text/AtomicString.h"
 
 namespace WebCore {
 
-class RenderStyle;
-class StyleResolverState;
+class StyleSheetContents;
 
-struct CachedMatchedProperties {
-    Vector<MatchedProperties> matchedProperties;
-    MatchRanges ranges;
-    RefPtr<RenderStyle> renderStyle;
-    RefPtr<RenderStyle> parentRenderStyle;
+class StyleSheetContentsCacheItem : public RefCounted<StyleSheetContentsCacheItem> {
+public:
+    static PassRefPtr<StyleSheetContentsCacheItem> create(StyleSheetContents*);
 
-    void set(const RenderStyle*, const RenderStyle* parentStyle, const MatchResult&);
-    void clear();
+    StyleSheetContents* contents() { return m_contents.get(); }
+
+private:
+    StyleSheetContentsCacheItem(PassRefPtr<StyleSheetContents> contents) : m_contents(contents) { }
+
+    RefPtr<StyleSheetContents> m_contents;
 };
 
-class MatchedPropertiesCache {
-    WTF_MAKE_NONCOPYABLE(MatchedPropertiesCache);
+class StyleSheetContentsCache {
+    WTF_MAKE_NONCOPYABLE(StyleSheetContentsCache);
 public:
-    MatchedPropertiesCache();
+    StyleSheetContentsCache();
 
-    const CachedMatchedProperties* find(unsigned hash, const StyleResolverState&, const MatchResult&);
-    void add(const RenderStyle*, const RenderStyle* parentStyle, unsigned hash, const MatchResult&);
-
+    StyleSheetContents* find(const AtomicString& sheetText);
+    void add(const AtomicString& sheetText, StyleSheetContents*);
+    void remove(const AtomicString& sheetText);
     void clear();
 
-    static bool isCacheable(const Element*, const RenderStyle*, const RenderStyle* parentStyle);
-
 private:
-    // Every N additions to the matched declaration cache trigger a sweep where entries holding
-    // the last reference to a style declaration are garbage collected.
-    void sweep(Timer<MatchedPropertiesCache>*);
+    void sweep(Timer<StyleSheetContentsCache>*);
 
     unsigned m_additionsSinceLastSweep;
 
-    typedef HashMap<unsigned, OwnPtr<CachedMatchedProperties> > Cache;
+    typedef HashMap<AtomicString, RefPtr<StyleSheetContentsCacheItem> > Cache;
     Cache m_cache;
 
-    Timer<MatchedPropertiesCache> m_sweepTimer;
+    Timer<StyleSheetContentsCache> m_sweepTimer;
 };
 
 }
 
 #endif