Avoid reaching for StyleResolver::m_features from StyleBuilder.

Source/core/css/resolver/StyleResolverState.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple 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,
@@ skipping 58 matching lines @@
     // FIXME: These are effectively side-channel "out parameters" for the various
     // map functions. When we map from CSS to style objects we use this state object
     // to track various meta-data about that mapping (e.g. if it's cache-able).
     // We need to move this data off of StyleResolverState and closer to the
     // objects it applies to. Possibly separating (immutable) inputs from (mutable) outputs.
     void setApplyPropertyToRegularStyle(bool isApply) { m_applyPropertyToRegularStyle = isApply; }
     void setApplyPropertyToVisitedLinkStyle(bool isApply) { m_applyPropertyToVisitedLinkStyle = isApply; }
     bool applyPropertyToRegularStyle() const { return m_applyPropertyToRegularStyle; }
     bool applyPropertyToVisitedLinkStyle() const { return m_applyPropertyToVisitedLinkStyle; }
 
+    // Holds all attribute names found while applying "content" properties that contain an "attr()" value.
+    Vector<AtomicString>& contentAttrValues() { return m_contentAttrValues; }
+
     void setLineHeightValue(CSSValue* value) { m_lineHeightValue = value; }
     CSSValue* lineHeightValue() { return m_lineHeightValue; }
 
     void cacheUserAgentBorderAndBackground() { m_cachedUAStyle = CachedUAStyle(style()); }
     const CachedUAStyle& cachedUAStyle() const { return m_cachedUAStyle; }
 
     ElementStyleResources& elementStyleResources() { return m_elementStyleResources; }
     const CSSToStyleMap& styleMap() const { return m_styleMap; }
     CSSToStyleMap& styleMap() { return m_styleMap; }
 
@@ skipping 52 matching lines @@
     CSSValue* m_lineHeightValue;
 
     FontBuilder m_fontBuilder;
 
     CachedUAStyle m_cachedUAStyle;
 
     ElementStyleResources m_elementStyleResources;
     // CSSToStyleMap is a pure-logic class and only contains
     // a back-pointer to this object.
     CSSToStyleMap m_styleMap;
+    Vector<AtomicString> m_contentAttrValues;
 };
 
 } // namespace WebCore
 
 #endif // StyleResolverState_h