Avoid unnecessary invalidations on resize.

Source/core/rendering/FastTextAutosizer.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 57 matching lines @@
 
     class LayoutScope {
     public:
         explicit LayoutScope(RenderBlock*);
         ~LayoutScope();
     private:
         FastTextAutosizer* m_textAutosizer;
         RenderBlock* m_block;
     };
 
+    class DeferUpdatePageInfo {
+    public:
+        explicit DeferUpdatePageInfo(Page*);
+        ~DeferUpdatePageInfo();
+    private:
+        RefPtr<LocalFrame> m_mainFrame;
+    };
+
 private:
     typedef HashSet<const RenderBlock*> BlockSet;
 
     enum HasEnoughTextToAutosize {
         UnknownAmountOfText,
         HasEnoughText,
         NotEnoughText
     };
 
     enum RelayoutBehavior {
@@ skipping 139 matching lines @@
     // from descendant clusters but because descendant clusters may not exist, this is only an approximation.
     // The TraversalDirection controls whether we return the first or the last text leaf.
     const RenderObject* findTextLeaf(const RenderObject*, size_t&, TextLeafSearch);
 
     const Document* m_document;
     int m_frameWidth; // LocalFrame width in density-independent pixels (DIPs).
     int m_layoutWidth; // Layout width in CSS pixels.
     float m_baseMultiplier; // Includes accessibility font scale factor and device scale adjustment.
     bool m_pageNeedsAutosizing;
     bool m_previouslyAutosized;
+    bool m_updatePageInfoDeferred;
     const RenderBlock* m_firstBlock; // First block to receive beginLayout.
 #ifndef NDEBUG
     BlockSet m_blocksThatHaveBegunLayout; // Used to ensure we don't compute properties of a block before beginLayout() is called on it.
 #endif
 
     // Clusters are created and destroyed during layout. The map key is the
     // cluster root. Clusters whose roots share the same fingerprint use the
     // same multiplier.
     SuperclusterMap m_superclusters;
     ClusterStack m_clusterStack;
     FingerprintMapper m_fingerprintMapper;
 };
 
 } // namespace WebCore
 
 #endif // FastTextAutosizer_h