Derive users to notify from user streams in on_new_event

Otherwise we were completely ignoring all users discovered from rooms being passed
to this function.

synapse/handlers/device.py

@@ -495,13 +495,11 @@ class DeviceHandler(DeviceWorkerHandler):
                 "Notifying about update %r/%r, ID: %r", user_id, device_id, position
             )
 
-        room_ids = await self.store.get_rooms_for_user(user_id)
-
         # specify the user ID too since the user should always get their own device list
         # updates, even if they aren't in any rooms.
-        self.notifier.on_new_event(
-            "device_list_key", position, users=[user_id], rooms=room_ids
-        )
+        users_to_notify = users_who_share_room.union(user_id)
+
+        self.notifier.on_new_event("device_list_key", position, users=users_to_notify)
 
         if hosts:
             logger.info(

synapse/notifier.py

@@ -458,7 +458,7 @@ class Notifier:
                 self.appservice_handler.notify_interested_services_ephemeral(
                     stream_key,
                     new_token,
-                    users,
+                    [UserID.from_string(user_stream.user_id) for user_stream in user_streams],
                 )
             except Exception:
                 logger.exception(