This cl creates BatteryHeaderPreferenceController, which will first load the battery level in ui thread(in displayPreference()), then display the remaining time once we get the battery stats. This is the best we can do to avoid ui flashing while removing the animation Bug: 38349587 Test: RunSettingsRoboTests Change-Id: Ic3622bb73562ba42e69b37e5674a724c03c45f12