MacViews: Use RenderTextHarfBuzz only for Textfields

ui/gfx/render_text.h

Index: ui/gfx/render_text.h
diff --git a/ui/gfx/render_text.h b/ui/gfx/render_text.h
index 9dc353ade39964403541e956d9a602c1d338f3ff..8153a1ec0425cabaa28e021baafa7712f1750a0f 100644
--- a/ui/gfx/render_text.h
+++ b/ui/gfx/render_text.h
@@ -191,6 +191,10 @@ class GFX_EXPORT RenderText {
 
   // Creates a platform-specific or cross-platform RenderText instance.
   static RenderText* CreateInstance();
+  static RenderText* CreateInstanceForEditing();
+
+  // Creates another instance of the same concrete class.
+  virtual scoped_ptr<RenderText> CreateInstanceOfSameType() const = 0;
 
   const base::string16& text() const { return text_; }
   void SetText(const base::string16& text);