Update CUPS settings UI to allow USB printers to be added via discovery.

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 92 matching lines @@
     this.fire('open-manually-add-printer-dialog');
   },
 
   /** @private */
   onCancelTap_: function() {
     this.stopDiscoveringPrinters_();
     this.$$('add-printer-dialog').close();
   },
 
   /** @private */
-  switchToConfiguringDialog_: function() {
+  switchToManufacturerDialog_: function() {
     this.stopDiscoveringPrinters_();
     this.$$('add-printer-dialog').close();
-    this.fire('open-configuring-printer-dialog');
+    this.fire('open-manufacturer-model-dialog');
   },
 });
 
 Polymer({
   is: 'add-printer-manually-dialog',
 
   properties: {
     /** @type {!CupsPrinterInfo} */
     newPrinter: {
       type: Object,
@@ skipping 55 matching lines @@
 Polymer({
   is: 'add-printer-manufacturer-model-dialog',
 
   properties: {
     /** @type {!CupsPrinterInfo} */
     newPrinter: {
       type: Object,
       notify: true,
     },
 
+    /** @type {!CupsPrinterInfo} */
+    selectedPrinter: {
+      type: Object,
+      notify: true,
+    },
+
     /** @type {?Array<string>} */
     manufacturerList: {
       type: Array,
     },
 
     /** @type {?Array<string>} */
     modelList: {
       type: Array,
     },
 
@@ skipping 127 matching lines @@
     newPrinter: {
       type: Object,
     },
 
     /** @type {boolean} whether the new printer setup is failed. */
     setupFailed: {
       type: Boolean,
       value: false,
     },
 
+    /**
+     * @type {boolean} whether we're doing manufacturer/model in
+     *       a manual flow (as opposed to a discovery flow).
+     * @private
+     */
+    inManualFlow: {
+      type: Boolean,
+      value: false,
+    },
+
     configuringDialogTitle: String,
 
     /** @private {string} */
     previousDialog_: String,
 
     /** @private {string} */
     currentDialog_: String,
 
     /** @private {boolean} */
     showDiscoveryDialog_: Boolean,
@@ skipping 17 matching lines @@
   },
 
   /** @override */
   ready: function() {
     this.addWebUIListener('on-add-cups-printer', this.onAddPrinter_.bind(this));
   },
 
   /** Opens the Add printer discovery dialog. */
   open: function() {
     this.resetData_();
-    this.switchDialog_(
-        '', AddPrinterDialogs.MANUALLY, 'showManuallyAddDialog_');
+    this.switchDialog_('', AddPrinterDialogs.DISCOVERY, 'showDiscoveryDialog_');
   },
 
   /**
    * Reset all the printer data in the Add printer flow.
    * @private
    */
   resetData_: function() {
     if (this.selectedPrinter)
       this.selectedPrinter = this.getEmptyPrinter_();
     if (this.newPrinter)
@@ skipping 47 matching lines @@
           loadTimeData.getString('addPrintersManuallyTitle');
       settings.CupsPrintersBrowserProxyImpl.getInstance().addCupsPrinter(
           this.newPrinter);
     }
   },
 
   /** @private */
   openManufacturerModelDialog_: function() {
     this.switchDialog_(this.currentDialog_, AddPrinterDialogs.MANUFACTURER,
                        'showManufacturerDialog_');
+    this.inManualFlow = false;
+    if (this.previousDialog_ == AddPrinterDialogs.MANUALLY) {
+      this.inManualFlow = true;
+    } else if (this.previousDialog_ == AddPrinterDialogs.DISCOVERY) {
+      // If we come to the manufacturer-model dialog via discovery, then the new
+      // printer we're working with is the selected one, so copy it over.  If we
+      // have a manufacturer entry from detection we'll leave it intact, but
+      // clear any manufacturer/model entries since the fact that we need to
+      // have the user select means we don't think we have the right one.
+      this.newPrinter = Object.assign({}, this.selectedPrinter);

[xdai1, 2017/05/10 20:12:53]

The reason I prefer not "copying fields over" either in top-level dialog or in
low-level dialog is the printer data from two flows (auto-discovery and manual)
are not mixed up. 

[Carlson, 2017/05/10 21:28:18]

I think I understand this now.  Replied at top level

+      this.newPrinter.printerManufacturer = '';
+      this.newPrinter.printerModel = '';
+      this.newPrinter.printerPPDPath = '';
+    }
   },
 
   /** @private */
   configuringDialogClosed_: function() {
     if (this.previousDialog_ == AddPrinterDialogs.MANUALLY) {
       this.switchDialog_(
           this.currentDialog_, this.previousDialog_, 'showManuallyAddDialog_');
     } else if (this.previousDialog_ == AddPrinterDialogs.MANUFACTURER) {
       this.switchDialog_(
           this.currentDialog_, this.previousDialog_, 'showManufacturerDialog_');
@@ skipping 43 matching lines @@
   onAddPrinter_: function(success, printerName) {
     this.$$('add-printer-configuring-dialog').close();
     if (success)
       return;
 
     if (this.previousDialog_ == AddPrinterDialogs.MANUFACTURER) {
       this.setupFailed = true;
     }
   },
 });