Add Mojo IPC based input-device service.

components/mus/public/interfaces/input_devices/input_devices.mojom

Index: components/mus/public/interfaces/input_devices/input_devices.mojom
diff --git a/components/mus/public/interfaces/input_devices/input_devices.mojom b/components/mus/public/interfaces/input_devices/input_devices.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;
+
+import "ui/gfx/geometry/mojo/geometry.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;
+};
+
+// TODO(kylechar): Don't repeat all the fields here, maybe just use composition.
+struct TouchscreenDevice {
+  // 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;
+  
+  // Size of the touch screen area.
+  gfx.mojom.Size size;
+  
+  // The number of touch points this device supports, or 0 if unknown.
+  int32 touch_points;
+};
+
+interface InputDeviceObserverMojo {
+  OnKeyboardDeviceConfigurationChanged(array<InputDevice> devices);
+  OnTouchscreenDeviceConfigurationChanged(array<TouchscreenDevice> devices);
+  OnMouseDeviceConfigurationChanged(array<InputDevice> devices);
+  OnTouchpadDeviceConfigurationChanged(array<InputDevice> devices);
+  OnDeviceListsComplete();
+};
+
+interface InputDeviceServer {
+  // Adds an InputDeviceObserverMojo in another process as an observer to get
+  // notified of changes to input-devices over Mojo IPC.
+  AddObserver(InputDeviceObserverMojo observer);
+};