Empty @viewport should not override legacy viewport.

Source/core/css/resolver/StyleResolver.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 251 matching lines @@
 
     // FIXME: Rename to reflect the purpose, like didChangeFontSize or something.
     void invalidateMatchedPropertiesCache();
 
     // Exposed for RenderStyle::isStyleAvilable().
     static RenderStyle* styleNotYetAvailable() { return s_styleNotYetAvailable; }
 
     // FIXME: StyleResolver should not have this member or method.
     InspectorCSSOMWrappers& inspectorCSSOMWrappers() { return m_inspectorCSSOMWrappers; }
 
-    enum ViewportOrigin { UserAgentOrigin, AuthorOrigin };
-
-    // Exposed for ScopedStyleResolver.
-    // FIXME: Likely belongs on viewportStyleResolver.
-    void collectViewportRules(RuleSet*, ViewportOrigin);
-
     const RuleFeatureSet& ruleFeatureSet() const { return m_features; }
 
     StyleSharingList& styleSharingList() { return m_styleSharingList; }
 
     bool supportsStyleSharing(Element*);
 
     void addToStyleSharingList(Element*);
     void clearStyleSharingList();
 
 #ifdef STYLE_STATS
@@ skipping 97 matching lines @@
         PseudoId ignoreDynamicPseudo = NOPSEUDO;
         if (selectorChecker.match(selectorCheckingContext, ignoreDynamicPseudo, DOMSiblingTraversalStrategy()) == SelectorChecker::SelectorMatches)
             return true;
     }
     return false;
 }
 
 } // namespace WebCore
 
 #endif // StyleResolver_h