map: add demo map data.

modules/common/data/global_flagfile.txt

@@ -5,5 +5,9 @@
 # 3. To override the flag values, you must set it after this file, as all Flags
 #    are evaluated strictly in order.
 
---map_dir=modules/map/data/new_garage
 --vehicle_config_path=modules/common/data/mkz_config.pb.txt
+
+--map_dir=modules/map/data/demo
+--base_map_filename=base_map.xml.txt
+--routing_map_filename=routing_map.txt
+--sim_map_filename=sim_map.txt
\ No newline at end of file