StyleSheetContents doesn't need a set of clients.

sky/engine/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 262 matching lines @@
     if (scope == m_document)
         return;
     m_dirtyTreeScopes.add(&scope);
 }
 
 PassRefPtr<CSSStyleSheet> StyleEngine::createSheet(Element* e, const String& text)
 {
     RefPtr<CSSStyleSheet> styleSheet;
     AtomicString textContent(text);
 
-    HashMap<AtomicString, RawPtr<StyleSheetContents> >::AddResult result = m_textToSheetCache.add(textContent, nullptr);
+    HashMap<AtomicString, StyleSheetContents*>::AddResult result = m_textToSheetCache.add(textContent, nullptr);
     if (result.isNewEntry || !result.storedValue->value) {
         styleSheet = CSSStyleSheet::create(e, KURL());
         styleSheet->contents()->parseString(text);
         if (result.isNewEntry) {
             result.storedValue->value = styleSheet->contents();
             m_sheetToTextCache.add(styleSheet->contents(), textContent);
         }
     } else {
         StyleSheetContents* contents = result.storedValue->value;
         ASSERT(contents);
         styleSheet = CSSStyleSheet::create(contents, e);
     }
 
     ASSERT(styleSheet);
     return styleSheet;
 }
 
 void StyleEngine::removeSheet(StyleSheetContents* contents)
 {
-    HashMap<RawPtr<StyleSheetContents>, AtomicString>::iterator it = m_sheetToTextCache.find(contents);
+    HashMap<StyleSheetContents*, AtomicString>::iterator it = m_sheetToTextCache.find(contents);
     if (it == m_sheetToTextCache.end())
         return;
 
     m_textToSheetCache.remove(it->value);
     m_sheetToTextCache.remove(contents);
 }
 
 // TODO(esprehn): This walks the entire document to collect features, instead
 // we should store features per scope and get rid of the global set.
 static void collectFeatures(TreeScope& scope, RuleFeatureSet& features, HashSet<const StyleSheetContents*> visitedSharedStyleSheetContents)
@@ skipping 12 matching lines @@
 }
 
 void StyleEngine::fontsNeedUpdate(CSSFontSelector*)
 {
     if (m_resolver)
         m_resolver->invalidateMatchedPropertiesCache();
     m_document->setNeedsStyleRecalc(SubtreeStyleChange);
 }
 
 }