nsIDOMWindowUtils
deprecated since gecko 38.0 key_flag_location_left 0x0020 location attrubute of the sending key event by sendkeyevent() returns keyboardevent.dom_key_location_left if this is specified to the aadditionalflags.

KeyboardEvent.location - Web APIs
dom_key_location_left 1 the key was the left-hand version of the key; for example, the left-hand control key was pressed on a standard 101 key us keyboard.

KeyboardEvent - Web APIs
dom_key_location_left 0x01 the key is one which may exist in multiple locations on the keyboard and, in this instance, is on the left side of the keyboard.