Add Mojo IPC based input-device service.

ui/events/devices/input_device_service.cc

Index: ui/events/devices/input_device_service.cc
diff --git a/ui/events/devices/input_device_service.cc b/ui/events/devices/input_device_service.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d5ef1323956a92f5720f52803e1ede75c9621d4c
--- /dev/null
+++ b/ui/events/devices/input_device_service.cc
@@ -0,0 +1,25 @@
+// 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.
+
+#include "ui/events/devices/input_device_service.h"
+
+namespace ui {
+
+InputDeviceService* InputDeviceService::instance_ = nullptr;
+
+InputDeviceService* InputDeviceService::GetInstance() {
+  DCHECK(instance_);
+  return instance_;
+}
+
+void InputDeviceService::SetInstance(InputDeviceService* instance) {
+  DCHECK(!instance_);
+  instance_ = instance;
+}
+
+void InputDeviceService::ClearInstance() {
+  instance_ = nullptr;
+}
+
+}  // namespace ui