Revise the shelf alignment locking mechanism.

ash/content/keyboard_overlay/keyboard_overlay_delegate_unittest.cc

 // Copyright (c) 2013 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 "ash/content/keyboard_overlay/keyboard_overlay_delegate.h"
 
 #include "ash/shelf/shelf_types.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 45 matching lines @@
 
   // Clean up.
   widget->CloseNow();
 }
 
 // Tests run three times - for all possible values of shelf alignment
 INSTANTIATE_TEST_CASE_P(ShelfAlignmentAny,
                         KeyboardOverlayDelegateTest,
                         testing::Values(SHELF_ALIGNMENT_BOTTOM,
                                         SHELF_ALIGNMENT_LEFT,
-                                        SHELF_ALIGNMENT_RIGHT));
+                                        SHELF_ALIGNMENT_RIGHT,
+                                        SHELF_ALIGNMENT_LOCKED));
 
 }  // namespace ash