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

chrome/browser/chromeos/chrome_browser_main_chromeos.cc

Index: chrome/browser/chromeos/chrome_browser_main_chromeos.cc
===================================================================
--- chrome/browser/chromeos/chrome_browser_main_chromeos.cc	(revision 201865)
+++ chrome/browser/chromeos/chrome_browser_main_chromeos.cc	(working copy)
@@ -73,6 +73,7 @@
 #include "chrome/browser/chromeos/settings/device_settings_service.h"
 #include "chrome/browser/chromeos/settings/owner_key_util.h"
 #include "chrome/browser/chromeos/system/automatic_reboot_manager.h"
+#include "chrome/browser/chromeos/system/device_change_handler.h"
 #include "chrome/browser/chromeos/system/statistics_provider.h"
 #include "chrome/browser/chromeos/system_key_event_listener.h"
 #include "chrome/browser/chromeos/upgrade_detector_chromeos.h"
@@ -739,6 +740,9 @@
   // available.
   idle_action_warning_observer_.reset(new IdleActionWarningObserver());
 
+  // Listen to changes in device hierarchy.
+  device_change_handler_.reset(new system::DeviceChangeHandler());
+
   ChromeBrowserMainPartsLinux::PostProfileInit();
 }