Oilpan: promptly dispose style resolvers upon clearing.

third_party/WebKit/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 409 matching lines @@
     // removes treescopes which are being destroyed from activeTreeScopes.
     // So we need to clearScopedStyleResolver for treescopes which have been
     // just removed from document. If document is destroyed before invoking
     // updateActiveStyleSheets, the treescope has a scopedStyleResolver which
     // has destroyed StyleSheetContents.
     for (TreeScope* treeScope : m_activeTreeScopes)
         treeScope->clearScopedStyleResolver();
 
     if (m_resolver) {
         TRACE_EVENT1("blink", "StyleEngine::clearResolver", "frame", document().frame());
+#if ENABLE(OILPAN)
+        // The StyleResolver is a heavy object having a number of collection objects
+        // attached. Attempt to promptly recycle their backing storage objects which
+        // are on the Oilpan collection heaps, so as to increase the chance of
+        // heap storage reuse without having to involve the Oilpan GC. Helpful for
+        // workloads that stresses (re)creation of StyleResolvers and/or have high
+        // allocation rates.
+        m_resolver->dispose();
+#endif
         m_resolver.clear();
     }
 }
 
 void StyleEngine::clearMasterResolver()
 {
     if (Document* master = this->master())
         master->styleEngine().clearResolver();
 }
 
@@ skipping 286 matching lines @@
     visitor->trace(m_dirtyTreeScopes);
     visitor->trace(m_activeTreeScopes);
     visitor->trace(m_fontSelector);
     visitor->trace(m_textToSheetCache);
     visitor->trace(m_sheetToTextCache);
 #endif
     CSSFontSelectorClient::trace(visitor);
 }
 
 }