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

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

Index: chrome/browser/resources/settings/printing_page/cups_add_printer_dialog.js
diff --git a/chrome/browser/resources/settings/printing_page/cups_add_printer_dialog.js b/chrome/browser/resources/settings/printing_page/cups_add_printer_dialog.js
index d2270f7c1a2fe01b487d5cc35d01b936cc3ae8d7..c18106bb69e79391009ea1cd0d06d2ee87920f0c 100644
--- a/chrome/browser/resources/settings/printing_page/cups_add_printer_dialog.js
+++ b/chrome/browser/resources/settings/printing_page/cups_add_printer_dialog.js
@@ -110,10 +110,10 @@ Polymer({
   },
 
   /** @private */
-  switchToConfiguringDialog_: function() {
+  switchToManufacturerDialog_: function() {
     this.stopDiscoveringPrinters_();
     this.$$('add-printer-dialog').close();
-    this.fire('open-configuring-printer-dialog');
+    this.fire('open-manufacturer-model-dialog');
   },
 });
 
@@ -189,6 +189,12 @@ Polymer({
       notify: true,
     },
 
+    /** @type {!CupsPrinterInfo} */
+    selectedPrinter: {
+      type: Object,
+      notify: true,
+    },
+
     /** @type {?Array<string>} */
     manufacturerList: {
       type: Array,
@@ -336,6 +342,16 @@ Polymer({
       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} */
@@ -373,8 +389,7 @@ Polymer({
   /** Opens the Add printer discovery dialog. */
   open: function() {
     this.resetData_();
-    this.switchDialog_(
-        '', AddPrinterDialogs.MANUALLY, 'showManuallyAddDialog_');
+    this.switchDialog_('', AddPrinterDialogs.DISCOVERY, 'showDiscoveryDialog_');
   },
 
   /**
@@ -442,6 +457,20 @@ Polymer({
   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 */