Use helper DeviceChangeHandler to call mousecontrol/tpcontrol whenever a device is attached.

chrome/browser/chromeos/system/device_change_handler.h

Index: chrome/browser/chromeos/system/device_change_handler.h
===================================================================
--- chrome/browser/chromeos/system/device_change_handler.h	(revision 0)
+++ chrome/browser/chromeos/system/device_change_handler.h	(revision 0)
@@ -0,0 +1,33 @@
+// Copyright (c) 2013 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 CHROME_BROWSER_CHROMEOS_SYSTEM_DEVICE_CHANGE_HANDLER_H_
+#define CHROME_BROWSER_CHROMEOS_SYSTEM_DEVICE_CHANGE_HANDLER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/chromeos/system/pointer_device_observer.h"
+
+namespace chromeos {
+namespace system {
+
+// Observes changes in device hierarchy. When a new touchpad/mouse is attached,
+// applies the last used profile's touchpad/mouse settings to the system.
+class DeviceChangeHandler : public PointerDeviceObserver::Observer {
+ public:
+  DeviceChangeHandler();
+  virtual ~DeviceChangeHandler();
+
+ private:
+  // PointerDeviceObserver::Observer implementation.
+  virtual void TouchpadExists(bool exists) OVERRIDE;
+  virtual void MouseExists(bool exists) OVERRIDE;
+
+  scoped_ptr<PointerDeviceObserver> pointer_device_observer_;
+};
+
+}  // namespace system
+}  // namesspace chromeos
+
+
+#endif  // CHROME_BROWSER_CHROMEOS_SYSTEM_DEVICE_CHANGE_HANDLER_H_