[CUPS] Change manufacturer selection should clear model selection in the dropdown list.

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 204 matching lines @@
         getCupsPrinterManufacturersList().then(
             this.manufacturerListChanged_.bind(this));
   },
 
   /**
    * @param {string} manufacturer The manufacturer for which we are retrieving
    *     models.
    * @private
    */
   selectedManufacturerChanged_: function(manufacturer) {
+    // Reset model if manufacturer is changed.
+    this.set('newPrinter.printerModel', '');
     if (manufacturer) {
       settings.CupsPrintersBrowserProxyImpl.getInstance()
           .getCupsPrinterModelsList(manufacturer)
           .then(this.modelListChanged_.bind(this));
     }
   },
 
   /** @private */
   onBrowseFile_: function() {
     settings.CupsPrintersBrowserProxyImpl.getInstance().
@@ skipping 263 matching lines @@
   onAddPrinter_: function(success, printerName) {
     this.$$('add-printer-configuring-dialog').close();
     if (success)
       return;
 
     if (this.previousDialog_ == AddPrinterDialogs.MANUFACTURER) {
       this.setupFailed = true;
     }
   },
 });