Fix the Views combobox on GTK by adding a new function.

views/controls/combobox/native_combobox_gtk.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved. Use of this
 // source code is governed by a BSD-style license that can be found in the
 // LICENSE file.
 
 #include "views/controls/combobox/native_combobox_gtk.h"
 
 #include "base/logging.h"
 #include "views/controls/combobox/combobox.h"
 
 namespace views {
@@ skipping 39 matching lines @@
 }
 
 View* NativeComboboxGtk::GetView() {
   return this;
 }
 
 void NativeComboboxGtk::SetFocus() {
   Focus();
 }
 
+gfx::NativeView NativeComboboxGtk::GetTestingHandle() const {
+  return native_view();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // NativeComboboxGtk, NativeControlGtk overrides:
 
 void NativeComboboxGtk::CreateNativeControl() {
 }
 
 void NativeComboboxGtk::NativeControlCreated(GtkWidget* native_control) {
   NativeControlGtk::NativeControlCreated(native_control);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativeComboboxWrapper, public:
 
 // static
 NativeComboboxWrapper* NativeComboboxWrapper::CreateWrapper(
     Combobox* combobox) {
   return new NativeComboboxGtk(combobox);
 }
 
 }  // namespace views