Remove unused `update_external_syncs`

This method isn't used anywhere. Burninate it.

synapse/handlers/presence.py

@@ -463,61 +463,6 @@ class PresenceHandler(object):
             syncing_user_ids.update(user_ids)
         return syncing_user_ids
 
-    @defer.inlineCallbacks
-    def update_external_syncs(self, process_id, syncing_user_ids):
-        """Update the syncing users for an external process
-
-        Args:
-            process_id(str): An identifier for the process the users are
-                syncing against. This allows synapse to process updates
-                as user start and stop syncing against a given process.
-            syncing_user_ids(set(str)): The set of user_ids that are
-                currently syncing on that server.
-        """
-
-        # Grab the previous list of user_ids that were syncing on that process
-        prev_syncing_user_ids = (
-            self.external_process_to_current_syncs.get(process_id, set())
-        )
-        # Grab the current presence state for both the users that are syncing
-        # now and the users that were syncing before this update.
-        prev_states = yield self.current_state_for_users(
-            syncing_user_ids | prev_syncing_user_ids
-        )
-        updates = []
-        time_now_ms = self.clock.time_msec()
-
-        # For each new user that is syncing check if we need to mark them as
-        # being online.
-        for new_user_id in syncing_user_ids - prev_syncing_user_ids:
-            prev_state = prev_states[new_user_id]
-            if prev_state.state == PresenceState.OFFLINE:
-                updates.append(prev_state.copy_and_replace(
-                    state=PresenceState.ONLINE,
-                    last_active_ts=time_now_ms,
-                    last_user_sync_ts=time_now_ms,
-                ))
-            else:
-                updates.append(prev_state.copy_and_replace(
-                    last_user_sync_ts=time_now_ms,
-                ))
-
-        # For each user that is still syncing or stopped syncing update the
-        # last sync time so that we will correctly apply the grace period when
-        # they stop syncing.
-        for old_user_id in prev_syncing_user_ids:
-            prev_state = prev_states[old_user_id]
-            updates.append(prev_state.copy_and_replace(
-                last_user_sync_ts=time_now_ms,
-            ))
-
-        yield self._update_states(updates)
-
-        # Update the last updated time for the process. We expire the entries
-        # if we don't receive an update in the given timeframe.
-        self.external_process_last_updated_ms[process_id] = self.clock.time_msec()
-        self.external_process_to_current_syncs[process_id] = syncing_user_ids
-
     @defer.inlineCallbacks
     def update_external_syncs_row(self, process_id, user_id, is_syncing, sync_time_msec):
         """Update the syncing users for an external process as a delta.