views: provide feedback when editing fails

ui/views/controls/textfield/textfield.h

Index: ui/views/controls/textfield/textfield.h
diff --git a/ui/views/controls/textfield/textfield.h b/ui/views/controls/textfield/textfield.h
index 22ff37b869acab431c7710407f0566326106d93e..3d8bf9c7916a13b0fbbf4d124272ef04e331bab8 100644
--- a/ui/views/controls/textfield/textfield.h
+++ b/ui/views/controls/textfield/textfield.h
@@ -392,6 +392,10 @@ class VIEWS_EXPORT Textfield : public View,
   // Pastes the selection clipboard for the specified mouse event.
   void PasteSelectionClipboard(const ui::MouseEvent& event);
 
+  // Called whenever an editing operation fails to provide visual or audio

[sky, 2016/09/16 17:34:36]

Why the visual/audio-feedback description? Isn't this more of 'called when a
keyevent is not handled for any reason, including the text-field is supplied a
keyevent and is read-only.

[Elly Fong-Jones, 2016/09/19 11:28:57]

Done.

+  // feedback to the user.
+  void OnEditFailed();
+
   // The text model.
   std::unique_ptr<TextfieldModel> model_;