Restore states through a JSON store instead of recorder (#17270)

* Restore states through a JSON store

* Accept entity_id directly in restore state helper

* Keep states stored between runs for a limited time

* Remove warning

homeassistant/components/timer/__init__.py

@@ -12,9 +12,9 @@ import voluptuous as vol
 import homeassistant.util.dt as dt_util
 import homeassistant.helpers.config_validation as cv
 from homeassistant.const import (ATTR_ENTITY_ID, CONF_ICON, CONF_NAME)
-from homeassistant.helpers.entity import Entity
 from homeassistant.helpers.entity_component import EntityComponent
 from homeassistant.helpers.event import async_track_point_in_utc_time
+from homeassistant.helpers.restore_state import RestoreEntity
 
 
 _LOGGER = logging.getLogger(__name__)
@@ -97,7 +97,7 @@ async def async_setup(hass, config):
     return True
 
 
-class Timer(Entity):
+class Timer(RestoreEntity):
     """Representation of a timer."""
 
     def __init__(self, hass, object_id, name, icon, duration):
@@ -146,8 +146,7 @@ class Timer(Entity):
         if self._state is not None:
             return
 
-        restore_state = self._hass.helpers.restore_state
-        state = await restore_state.async_get_last_state(self.entity_id)
+        state = await self.async_get_last_state()
         self._state = state and state.state == state
 
     async def async_start(self, duration):