Clear CSSGlobalRuleSet on StyleEngine::didDetach().

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.
@@ skipping 439 matching lines @@
 
   if (m_resolver) {
     TRACE_EVENT1("blink", "StyleEngine::clearResolver", "frame",
                  document().frame());
     m_resolver->dispose();
     m_resolver.clear();
   }
 }
 
 void StyleEngine::didDetach() {
+  m_globalRuleSet.dispose();
   clearResolver();
   m_viewportResolver = nullptr;
   m_mediaQueryEvaluator = nullptr;
   clearFontCache();
 }
 
 void StyleEngine::clearFontCache() {
   if (m_fontSelector)
     m_fontSelector->fontFaceCache()->clearCSSConnected();
   if (m_resolver)
@@ skipping 671 matching lines @@
 }
 
 DEFINE_TRACE_WRAPPERS(StyleEngine) {
   for (auto sheet : m_injectedAuthorStyleSheets) {
     visitor->traceWrappers(sheet);
   }
   visitor->traceWrappers(m_documentStyleSheetCollection);
 }
 
 }  // namespace blink