Add Mojo IPC based input-device service.

ui/events/devices/input_device_service.h

Index: ui/events/devices/input_device_service.h
diff --git a/ui/events/devices/input_device_service.h b/ui/events/devices/input_device_service.h
new file mode 100644
index 0000000000000000000000000000000000000000..5f3a4668924e9f8a3b75958186566b652ea87f6a
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+++ b/ui/events/devices/input_device_service.h
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+// Copyright 2016 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 UI_EVENTS_DEVICES_INPUT_DEVICE_SERVICE_H_
+#define UI_EVENTS_DEVICES_INPUT_DEVICE_SERVICE_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "ui/events/devices/events_devices_export.h"
+#include "ui/events/devices/input_device.h"
+#include "ui/events/devices/input_device_event_observer.h"
+
+namespace ui {
+
+// Abstract interface to query about input devices that are available. Holds a
+// pointer to implementation that provides these services.
+// TODO(kylechar): DeviceDataManager should also implement this interface.
+class EVENTS_DEVICES_EXPORT InputDeviceService {
+ public:
+  InputDeviceService() {}
+
+  static InputDeviceService* GetInstance();
+
+  virtual void AddObserver(InputDeviceEventObserver* observer) = 0;
+  virtual void RemoveObserver(InputDeviceEventObserver* observer) = 0;
+
+  virtual const std::vector<InputDevice>& keyboard_devices() = 0;
+  virtual const std::vector<InputDevice>& touchscreen_devices() = 0;
+  virtual const std::vector<InputDevice>& mouse_devices() = 0;
+  virtual const std::vector<InputDevice>& touchpad_devices() = 0;
+
+ protected:
+  static void SetInstance(InputDeviceService* instance);
+  static void ClearInstance();
+
+ private:
+  static InputDeviceService* instance_;  // Not owned.
+
+  DISALLOW_COPY_AND_ASSIGN(InputDeviceService);
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_DEVICES_INPUT_DEVICE_SERVICE_H_