discourse/app/assets/javascripts/admin/components/theme-setting-editor.js.es6

import Component from "@ember/component";
import BufferedContent from "discourse/mixins/buffered-content";
import SettingComponent from "admin/mixins/setting-component";
import { ajax } from "discourse/lib/ajax";

export default Component.extend(BufferedContent, SettingComponent, {
  layoutName: "admin/templates/components/site-setting",

  _save() {
    return ajax(`/admin/themes/${this.model.id}/setting`, {
      type: "PUT",
      data: {
        name: this.setting.setting,
        value: this.get("buffered.value")
      }
    });
  }
});