Only the main document should have a StyleEngine.

sky/engine/core/dom/StyleEngine.h

 /*
  * 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, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 50 matching lines @@
         {
         }
     };
 
     friend class IgnoringPendingStylesheet;
 
     static PassOwnPtr<StyleEngine> create(Document& document) { return adoptPtr(new StyleEngine(document)); }
 
     ~StyleEngine();
 
-#if !ENABLE(OILPAN)
     void detachFromDocument();
-#endif
 
     const Vector<RefPtr<CSSStyleSheet>>& activeAuthorStyleSheetsFor(TreeScope&);
 
     void modifiedStyleSheet(CSSStyleSheet*);
     void addStyleSheetCandidateNode(Node*, bool createdByParser);
     void removeStyleSheetCandidateNode(Node*, ContainerNode* scopingNode, TreeScope&);
 
     void updateActiveStyleSheets();
 
     bool ignoringPendingStylesheets() const { return m_ignorePendingStylesheets; }
@@ skipping 14 matching lines @@
         if (!m_resolver) {
             createResolver();
         } else if (m_resolver->hasPendingAuthorStyleSheets()) {
             m_resolver->appendPendingAuthorStyleSheets();
         }
         return *m_resolver.get();
     }
 
     bool hasResolver() const { return m_resolver.get(); }
     void clearResolver();
-    void clearMasterResolver();
 
     CSSFontSelector* fontSelector() { return m_fontSelector.get(); }
     void removeFontFaceRules(const Vector<RawPtr<const StyleRuleFontFace> >&);
     void clearFontCache();
     // updateGenericFontFamilySettings is used from WebSettingsImpl.
     void updateGenericFontFamilySettings();
 
     void didDetach();
     void resolverChanged();
     unsigned resolverAccessCount() const;
 
-    void markDocumentDirty();
-
     PassRefPtr<CSSStyleSheet> createSheet(Element*, const String& text);
     void removeSheet(StyleSheetContents*);
 
     void addScopedStyleResolver(const ScopedStyleResolver* resolver) { m_scopedStyleResolvers.add(resolver); }
     void removeScopedStyleResolver(const ScopedStyleResolver* resolver) { m_scopedStyleResolvers.remove(resolver); }
     bool hasOnlyScopedResolverForDocument() const { return m_scopedStyleResolvers.size() == 1; }
     void collectScopedStyleFeaturesTo(RuleFeatureSet&) const;
 
 private:
     // CSSFontSelectorClient implementation.
     virtual void fontsNeedUpdate(CSSFontSelector*) override;
 
 private:
     StyleEngine(Document&);
 
     StyleSheetCollection* ensureStyleSheetCollectionFor(TreeScope&);
     StyleSheetCollection* styleSheetCollectionFor(TreeScope&);
 
     void markTreeScopeDirty(TreeScope&);
 
-    bool isMaster() const { return m_isMaster; }
-    Document* master();
-    Document& document() const { return *m_document; }
-
     typedef ListHashSet<TreeScope*, 16> TreeScopeSet;
     static void insertTreeScopeInDocumentOrder(TreeScopeSet&, TreeScope*);
 
     void createResolver();
 
     const StyleSheetCollection* documentStyleSheetCollection() const
     {
         return m_documentStyleSheetCollection.get();
     }
 
     StyleSheetCollection* documentStyleSheetCollection()
     {
         return m_documentStyleSheetCollection.get();
     }
 
     RawPtr<Document> m_document;
-    bool m_isMaster;
 
     // TODO(esprehn): Remove special separate collection for document.
     OwnPtr<StyleSheetCollection> m_documentStyleSheetCollection;
 
     typedef HashMap<RawPtr<TreeScope>, OwnPtr<StyleSheetCollection> > StyleSheetCollectionMap;
     StyleSheetCollectionMap m_styleSheetCollectionMap;
     typedef HashSet<RawPtr<const ScopedStyleResolver> > ScopedStyleResolverSet;
     ScopedStyleResolverSet m_scopedStyleResolvers;
 
-    bool m_documentScopeDirty;
     TreeScopeSet m_dirtyTreeScopes;
     TreeScopeSet m_activeTreeScopes;
 
     bool m_ignorePendingStylesheets;
     OwnPtr<StyleResolver> m_resolver;
 
     RefPtr<CSSFontSelector> m_fontSelector;
 
     HashMap<AtomicString, RawPtr<StyleSheetContents> > m_textToSheetCache;
     HashMap<RawPtr<StyleSheetContents>, AtomicString> m_sheetToTextCache;
 };
 
 }
 
 #endif  // SKY_ENGINE_CORE_DOM_STYLEENGINE_H_