[CUPS] Fix the issue the default queue value not being persisted with each new printer setup.

chrome/browser/resources/settings/printing_page/cups_add_printer_dialog.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-add-printer-dialog' includes multiple dialogs to
  * set up a new CUPS printer.
  * Subdialogs include:
  * - 'add-printer-discovery-dialog' is a dialog showing discovered printers on
  *   the network that are available for setup.
@@ skipping 117 matching lines @@
       value: function() {
         return {
           printerAddress: '',
           printerDescription: '',
           printerId: '',
           printerManufacturer: '',
           printerModel: '',
           printerName: '',
           printerPPDPath: '',
           printerProtocol: 'ipp',
-          printerQueue: 'ipp/print',
+          printerQueue: '',
           printerStatus: '',
         };
       },
     },
   },
 
   /** @private */
   switchToDiscoveryDialog_: function() {
     this.$$('add-printer-dialog').close();
     this.fire('open-discovery-printers-dialog');
   },
 
   /** @private */
   onCancelTap_: function() {
     this.$$('add-printer-dialog').close();
   },
 
   /** @private */
   switchToManufacturerDialog_: function() {
+    // Set the default printer queue to be "ipp/print".
+    if (!this.newPrinter.printerQueue)
+      this.set('newPrinter.printerQueue', 'ipp/print');
+
     this.$$('add-printer-dialog').close();
     this.fire('open-manufacturer-model-dialog');
   },
 
   /** @private */
   onAddressChanged_: function() {
     // TODO(xdai): Check if the printer address exists and then show the
     // corresponding message after the API is ready.
     // The format of address is: ip-address-or-hostname:port-number.
   },
 
   /**
    * @param {!Event} event
    * @private
    */
   onProtocolChange_: function(event) {
-    this.newPrinter.printerProtocol = event.target.value;
+    this.set('newPrinter.printerProtocol', event.target.value);
   },
 });
 
 Polymer({
   is: 'add-printer-manufacturer-model-dialog',
 
   properties: {
     /** @type {!CupsPrinterInfo} */
     newPrinter: {
       type: Object,
@@ skipping 44 matching lines @@
   onBrowseFile_: function() {
     settings.CupsPrintersBrowserProxyImpl.getInstance().
         getCupsPrinterPPDPath().then(this.printerPPDPathChanged_.bind(this));
   },
 
   /**
    * @param {string} path
    * @private
    */
   printerPPDPathChanged_: function(path) {
-    this.newPrinter.printerPPDPath = path;
+    this.set('newPrinter.printerPPDPath', path);
     this.$$('paper-input').value = this.getBaseName_(path);
   },
 
   /**
    * @param {!ManufacturersInfo} manufacturersInfo
    * @private
    */
   manufacturerListChanged_: function(manufacturersInfo) {
     if (manufacturersInfo.success)
       this.manufacturerList = manufacturersInfo.manufacturers;
@@ skipping 244 matching lines @@
   onAddPrinter_: function(success, printerName) {
     this.$$('add-printer-configuring-dialog').close();
     if (success)
       return;
 
     if (this.previousDialog_ == AddPrinterDialogs.MANUFACTURER) {
       this.setupFailed = true;
     }
   },
 });