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

Source/core/css/StyleSheetContentsCache.cpp

+/*
+ * 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.
+ *
+ */
+
+#include "config.h"
+#include "core/css/StyleSheetContentsCache.h"
+
+#include "core/css/StyleSheetContents.h"
+
+namespace WebCore {
+
+PassOwnPtr<CachedStyleSheetContents> CachedStyleSheetContents::create(StyleSheetContents* contents)
+{
+    ASSERT(contents);
+    ASSERT(contents->isCacheable());
+    return adoptPtr(new CachedStyleSheetContents(contents->copy()));
+}
+
+StyleSheetContentsCache::StyleSheetContentsCache()
+    : m_additionsSinceLastSweep(0)
+    , m_sweepTimer(this, &StyleSheetContentsCache::sweep)
+{
+}
+
+StyleSheetContents* StyleSheetContentsCache::find(const AtomicString& sheetText)
+{
+    if (sheetText.isEmpty())
+        return 0;
+
+    Cache::iterator it = m_cache.find(sheetText);
+    if (it == m_cache.end())
+        return 0;
+    return it->value->contents();
+}
+
+void StyleSheetContentsCache::add(const AtomicString& sheetText, StyleSheetContents* contents)
+{
+    static const unsigned maxAdditionsBetweenSweeps = 100;
+    if (++m_additionsSinceLastSweep >= maxAdditionsBetweenSweeps
+        && !m_sweepTimer.isActive()) {
+        static const unsigned sweepTimeInSeconds = 60;
+        m_sweepTimer.startOneShot(sweepTimeInSeconds);
+    }
+
+    ASSERT(contents);
+    ASSERT(!sheetText.isEmpty());
+
+    Cache::AddResult result = m_cache.add(sheetText, nullptr);
+    if (result.isNewEntry)
+        result.iterator->value = CachedStyleSheetContents::create(contents);
+
+    result.iterator->value->addref();
+}
+
+void StyleSheetContentsCache::remove(const AtomicString& sheetText)
+{
+    Cache::iterator it = m_cache.find(sheetText);
+    if (it == m_cache.end())
+        return;
+    if (it->value->deref())
+        return;
+    m_cache.remove(sheetText);
+}
+
+void StyleSheetContentsCache::sweep(Timer<StyleSheetContentsCache>*)
+{
+    // Look for cache entries containing a style declaration with a single ref and remove them.
+    Vector<AtomicString*, 16> toRemove;
+    Cache::iterator it = m_cache.begin();
+    Cache::iterator end = m_cache.end();
+    for (; it != end; ++it) {
+        CachedStyleSheetContents* cacheItem = it->value.get();
+        if (cacheItem->hasOneRef())

[dglazkov, 2013/10/21 18:24:10]

I see. Can you not just make them RefPtrs and sweep for 0s?

[tasak, 2013/10/25 05:23:13]

I see.
I changed the code to use RefPtrs and to remove cached items which are not
shared by any other style elements.

+            toRemove.append(&it->key);
+    }
+    for (size_t i = 0; i < toRemove.size(); ++i)
+        m_cache.remove(*toRemove[i]);
+
+    m_additionsSinceLastSweep = 0;
+}
+
+void StyleSheetContentsCache::clear()
+{
+    m_cache.clear();
+}
+
+}