Use css-device-adapt constraining for legacy viewport tags.

Source/core/css/resolver/ViewportStyleResolver.h

 /*
  * Copyright (C) 2012 Intel Corporation. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 32 matching lines @@
 
 class ViewportStyleResolver : public RefCounted<ViewportStyleResolver> {
 public:
     static PassRefPtr<ViewportStyleResolver> create(Document* document)
     {
         return adoptRef(new ViewportStyleResolver(document));
     }
 
     ~ViewportStyleResolver();
 
+    void setHasAuthorStyle() { m_hasAuthorStyle = true; }
     void addViewportRule(StyleRuleViewport*);
 
     void clearDocument();
     void resolve();
 
 private:
     explicit ViewportStyleResolver(Document*);
 
     float getViewportArgumentValue(CSSPropertyID) const;
     Length getViewportLengthValue(CSSPropertyID) const;
 
     Document* m_document;
     RefPtr<MutableStylePropertySet> m_propertySet;
+    bool m_hasAuthorStyle;
 };
 
 } // namespace WebCore
 
 #endif // ViewportStyleResolver_h