JS keymap: because of firefox send different eventname

jskeycodes.py

@@ -122,6 +122,10 @@ jskeycodes = {
     'KEY_MOD_LMETA': 'MetaLeft',
     'KEY_MOD_RMETA': 'MetaRight',
 
+# Because firefox must sending different
+    'KEY_MOD_LMETA': 'OSLeft',
+    'KEY_MOD_RMETA': 'OSRight',
+
     'KEY_COMPOSE': 'ContextMenu',
 }