Itemize and layout text lazily in RenderTextWin.

ui/gfx/render_text_win.h

Index: ui/gfx/render_text_win.h
===================================================================
--- ui/gfx/render_text_win.h	(revision 111162)
+++ ui/gfx/render_text_win.h	(working copy)
@@ -80,6 +80,7 @@
  private:
   virtual size_t IndexOfAdjacentGrapheme(size_t index, bool next) OVERRIDE;
 
+  void EnsureLayout();
   void ItemizeLogicalText();
   void LayoutVisualText();
 
@@ -116,6 +117,8 @@
   scoped_array<int> visual_to_logical_;
   scoped_array<int> logical_to_visual_;
 
+  bool needs_layout_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderTextWin);
 };