Make updateStyleAndLayoutTree ready for async stylesheet update.

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 33 matching lines @@
 
 class CORE_EXPORT ViewportStyleResolver
     : public GarbageCollected<ViewportStyleResolver> {
  public:
   static ViewportStyleResolver* create(Document& document) {
     return new ViewportStyleResolver(document);
   }
 
   void initialViewportChanged();
   void setNeedsCollectRules();
+  bool needsUpdate() const { return m_needsUpdate; }
   void updateViewport(DocumentStyleSheetCollection&);
 
   void collectViewportRulesFromAuthorSheet(const CSSStyleSheet&);
 
   DECLARE_TRACE();
 
  private:
   explicit ViewportStyleResolver(Document&);
 
   void reset();
@@ skipping 18 matching lines @@
   MediaQueryResultList m_viewportDependentMediaQueryResults;
   MediaQueryResultList m_deviceDependentMediaQueryResults;
   bool m_hasAuthorStyle = false;
   bool m_hasViewportUnits = false;
   UpdateType m_needsUpdate = CollectRules;
 };
 
 }  // namespace blink
 
 #endif  // ViewportStyleResolver_h