// Enumerate the devices in Device thread and post the consolidation of the
// new devices and the old ones to be done on UI thread. The devices array
// is retained in |device_thread| and released in DoOnDeviceChanged().
// Enumerate the devices in Device thread and post the consolidation of the
// new devices and the old ones to be done on UI thread. The devices array
// is retained in |device_thread| and released in DoOnDeviceChanged().