Don't generate RuleSets for viewport UA sheets.

third_party/WebKit/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 26 matching lines @@
 
 namespace blink {
 
 class Document;
 class MutableStylePropertySet;
 class StyleRuleViewport;
 
 class CORE_EXPORT ViewportStyleResolver
     : public GarbageCollected<ViewportStyleResolver> {
  public:
-  static ViewportStyleResolver* create(Document* document) {
+  static ViewportStyleResolver* create(Document& document) {
     return new ViewportStyleResolver(document);
   }
 
   enum Origin { UserAgentOrigin, AuthorOrigin };
 
   void collectViewportRules();
   void collectViewportRules(RuleSet*, Origin);
   void resolve();
 
   DECLARE_TRACE();
 
  private:
-  explicit ViewportStyleResolver(Document*);
+  explicit ViewportStyleResolver(Document&);
 
-  void addViewportRule(StyleRuleViewport*, Origin);
+  void collectViewportRulesFromUASheets();
+  void collectViewportChildRules(const HeapVector<Member<StyleRuleBase>>&,
+                                 Origin);
+  void addViewportRule(StyleRuleViewport&, Origin);
 
   float viewportArgumentValue(CSSPropertyID) const;
   Length viewportLengthValue(CSSPropertyID) const;
 
   Member<Document> m_document;
   Member<MutableStylePropertySet> m_propertySet;
+  Member<MediaQueryEvaluator> m_initialViewportMedium;
   bool m_hasAuthorStyle;
 };
 
 }  // namespace blink
 
 #endif  // ViewportStyleResolver_h