Add Mojo IPC based input-device service.

components/input_device_service/input_device_service.mojom

Index: components/input_device_service/input_device_service.mojom
diff --git a/components/input_device_service/input_device_service.mojom b/components/input_device_service/input_device_service.mojom
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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.
+
+module input_device.mojom;
+
+enum InputDeviceType {
+  INPUT_DEVICE_INTERNAL,  // Internally connected input device.
+  INPUT_DEVICE_EXTERNAL,  // Known externally connected input device.
+  INPUT_DEVICE_UNKNOWN,   // Device that may or may not be an external device.
+};
+
+struct InputDevice {
+  // ID of the device. This ID is unique between all input devices.
+  int32 id;
+
+  // The type of the input device.
+  InputDeviceType type;
+
+  // Name of the device.
+  string name;
+
+  // The path to the input device in the sysfs filesystem.
+  string sys_path;
+
+  // USB-style device identifiers, where available, or 0 if unavailable.
+  uint16 vendor_id;
+  uint16 product_id;
+};
+
+interface InputDeviceObserver {
+  OnKeyboardDeviceConfigurationChanged(array<InputDevice> devices);
+  OnTouchscreenDeviceConfigurationChanged(array<InputDevice> devices);
+  OnMouseDeviceConfigurationChanged(array<InputDevice> devices);
+  OnTouchpadDeviceConfigurationChanged(array<InputDevice> devices);
+};
+
+interface InputDeviceService {
+  // Adds an observer to be notified of changes to input devices over Mojo IPC.
+  AddObserver(InputDeviceObserver observer);
+  
+  // Gets list of keyboard input devices.
+  GetKeyboardDevices() => (array<InputDevice> devices);
+  
+  // Gets list of touchscreen input devices.
+  GetTouchscreenDevices() => (array<InputDevice> devices);
+  
+  // Gets list of mouse input devices.
+  GetMouseDevices() => (array<InputDevice> devices);
+  
+  // Gets list of touchpad input devices.
+  GetTouchpadDevices() => (array<InputDevice> devices);
+};