Merge NativeTextfieldViews into views::Textfield.

ui/views/controls/textfield/textfield_views_model.h

Index: ui/views/controls/textfield/textfield_views_model.h
diff --git a/ui/views/controls/textfield/textfield_views_model.h b/ui/views/controls/textfield/textfield_views_model.h
index bc1de8857529a59ccd7b62b62e15259fc311bb68..bc9e25643eff1190dec872c023e09066db80c6a1 100644
--- a/ui/views/controls/textfield/textfield_views_model.h
+++ b/ui/views/controls/textfield/textfield_views_model.h
@@ -226,9 +226,10 @@ class VIEWS_EXPORT TextfieldViewsModel {
   // Returns true if there is composition text.
   bool HasCompositionText() const;
 
+  // Clears all edit history.
+  void ClearEditHistory();
+
  private:
-  friend class NativeTextfieldViews;
-  friend class NativeTextfieldViewsTest;
   friend class TextfieldViewsModelTest;
   friend class UndoRedo_BasicTest;
   friend class UndoRedo_CutCopyPasteTest;
@@ -248,9 +249,6 @@ class VIEWS_EXPORT TextfieldViewsModel {
   // edit in the edit history.
   void ReplaceTextInternal(const base::string16& text, bool mergeable);
 
-  // Clears all edit history.
-  void ClearEditHistory();
-
   // Clears redo history.
   void ClearRedoHistory();