[CUPS] Implement the UI handler for adding a new printer.

chrome/browser/resources/settings/printing_page/cups_printers.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview 'settings-cups-printers' is a component for showing CUPS
  * Printer settings subpage (chrome://md-settings/cupsPrinters). It is used to
  * set up legacy & non-CloudPrint printers on ChromeOS by leveraging CUPS (the
  * unix printing system) and the many open source drivers built for CUPS.
  */
 // TODO(xdai): Rename it to 'settings-cups-printers-page'.
 Polymer({
   is: 'settings-cups-printers',
 
+  behaviors: [WebUIListenerBehavior],
+
   properties: {
     /** @type {!Array<!CupsPrinterInfo>} */
     printers: {
       type: Array,
       notify: true,
     },
 
     searchTerm: {
       type: String,
     },
   },
 
   /** @override */
   ready: function() {
+    this.updateCupsPrintersList_();
+    this.addWebUIListener('on-add-cups-printer', this.onAddPrinter_.bind(this));
+  },
+
+  /**
+   * @param {boolean} success
+   * @param {string} printerName
+   * @private
+   */
+  onAddPrinter_: function(success, printerName) {
+    if (!success)
+      return;
+
+    this.updateCupsPrintersList_();
+    var message = this.$.addPrinterMessage;
+    message.textContent = loadTimeData.getStringF(
+        'printerAddedSuccessfulMessage', printerName);
+    message.hidden = false;
+    window.setTimeout(function() {
+      message.hidden = true;
+    }, 3000);
+  },
+
+  /** @private */
+  updateCupsPrintersList_: function() {
     settings.CupsPrintersBrowserProxyImpl.getInstance().
         getCupsPrintersList().then(this.printersChanged_.bind(this));
   },
 
   /**
    * @param {!CupsPrintersList} cupsPrintersList
    * @private
    */
   printersChanged_: function(cupsPrintersList) {
     this.printers = cupsPrintersList.printerList;
   },
 
   /** @private */
   onAddPrinterTap_: function() {
     this.$.addPrinterDialog.open();
   },
 });