defaults.js: support custom arg in mp.add_key_binding()

player/javascript/defaults.js

@@ -246,10 +246,10 @@ mp.get_osd_margins = function get_osd_margins() {
 // {cb: fn, forced: bool, maybe input: str, repeatable: bool, complex: bool}
 var binds = new_cache();
 
-function dispatch_key_binding(name, state, key_name, key_text, scale) {
+function dispatch_key_binding(name, state, key_name, key_text, scale, arg) {
     var cb = binds[name] ? binds[name].cb : false;
     if (cb)  // "script-binding [<script_name>/]<name>" command was invoked
-        cb(state, key_name, key_text, scale);
+        cb(state, key_name, key_text, scale, arg);
 }
 
 var binds_tid = 0;  // flush timer id. actual id's are always true-thy
@@ -314,7 +314,8 @@ function add_binding(forced, key, name, fn, opts) {
                 canceled: state[2] == "c",
                 key_name: key_name || undefined,
                 key_text: key_text || undefined,
-                scale: scale ? parseFloat(scale) : 1.0
+                scale: scale ? parseFloat(scale) : 1.0,
+                arg: arg
             });
         }
     } else {
@@ -333,8 +334,11 @@ function add_binding(forced, key, name, fn, opts) {
     }
 
     var prefix = key_data.scalable ? "" : " nonscalable";
-    if (key)
+    if (key) {
         key_data.input = key + prefix + " script-binding " + mp.script_name + "/" + name;
+        if (key_data.arg)
+            key_data.input = key_data.input + " " + key_data.arg;
+    }
     binds[name] = key_data;  // used by user and/or our (key) script-binding
     sched_bindings_flush();
 }