Show overlay displaying the state of all sticky keys when it is enabled.

ash/sticky_keys/sticky_keys_constants.h

Index: ash/sticky_keys/sticky_keys_constants.h
diff --git a/ash/sticky_keys/sticky_keys_constants.h b/ash/sticky_keys/sticky_keys_constants.h
new file mode 100644
index 0000000000000000000000000000000000000000..ae90911f8d14f951e35f368be55ccdc5dec08471
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+++ b/ash/sticky_keys/sticky_keys_constants.h
@@ -0,0 +1,25 @@
+// Copyright 2014 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.
+
+#ifndef ASH_STICKY_KEYS_STICKY_KEYS_CONSTANTS_H_

[James Cook, 2014/01/16 17:45:59]

If you think this file will only contain the single enum I suggest naming it
sticky_keys_state.h.  If you think it will gain more constants leave it as is.

[Tim Song, 2014/01/16 19:11:56]

Done. Renamed to sticky_keys_state.h

+#define ASH_STICKY_KEYS_STICKY_KEYS_CONSTANTS_H_
+
+namespace ash {
+
+// State of an individual modifier key.
+enum StickyKeyState {
+  // The sticky key is disabled. Incoming non-modifier key events are not
+  // affected.
+  STICKY_KEY_STATE_DISABLED,
+  // The sticky key is enabled. Incoming non-modifier key down events are
+  // modified. After that, sticky key state becomes DISABLED.
+  STICKY_KEY_STATE_ENABLED,
+  // The sticky key is locked. All incoming non modifier key down events are
+  // modified.
+  STICKY_KEY_STATE_LOCKED,
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_STICKY_KEYS_CONTROLLER_H_