Revert of chromeos: Remove some IME methods from ash::SystemTrayDelegate

ash/ime/ime_switch_type.h

-// Copyright 2017 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_IME_IME_SWITCH_TYPE_H_
-#define ASH_IME_IME_SWITCH_TYPE_H_
-
-namespace ash {
-
-// Used for histograms. See tools/metrics/histograms/enums.xml IMESwitchType.
-enum class ImeSwitchType {
-  // The values should not reordered or deleted and new entries should only be
-  // added at the end (otherwise it will cause problems interpreting logs)
-  kTray = 0,
-  kAccelerator = 1,
-  kCount = 2,
-};
-
-}  // namespace ash
-
-#endif  // ASH_IME_IME_SWITCH_TYPE_H_