Consolidate save handling

Author: blink1073

lib/matplotlib/backends/web_backend/mpl.js

@@ -480,9 +480,7 @@ mpl.figure.prototype.key_event = function(event, name) {
 
 mpl.figure.prototype.toolbar_button_onclick = function(name) {
     if (name == 'download') {
-        var format_dropdown = this.format_dropdown;
-        var format = format_dropdown.options[format_dropdown.selectedIndex].value;
-        this.ondownload(this, format);
+        this.handle_save(this, null);
     } else {
         this.send_message("toolbar_button", {name: name});
     }