[CUPS] Implement the Webui handler for the printers auto discovery.

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

Index: chrome/browser/resources/settings/printing_page/cups_printers.js
diff --git a/chrome/browser/resources/settings/printing_page/cups_printers.js b/chrome/browser/resources/settings/printing_page/cups_printers.js
index 28f7f3c4c44dfdcaf18280383bac48ebc7a36e61..103bbb9d830ca45cf02e0302c18e37ee7e5f987c 100644
--- a/chrome/browser/resources/settings/printing_page/cups_printers.js
+++ b/chrome/browser/resources/settings/printing_page/cups_printers.js
@@ -38,13 +38,14 @@ Polymer({
    * @private
    */
   onAddPrinter_: function(success, printerName) {
-    if (!success)
-      return;
-
-    this.updateCupsPrintersList_();
-    var message = this.$.addPrinterMessage;
-    message.textContent = loadTimeData.getStringF(
-        'printerAddedSuccessfulMessage', printerName);
+    if (success) {
+      this.updateCupsPrintersList_();
+      var message = this.$.addPrinterDoneMessage;
+      message.textContent = loadTimeData.getStringF(
+          'printerAddedSuccessfulMessage', printerName);
+    } else {
+      var message = this.$.addPrinterErrorMessage;
+    }
     message.hidden = false;
     window.setTimeout(function() {
       message.hidden = true;
@@ -68,5 +69,6 @@ Polymer({
   /** @private */
   onAddPrinterTap_: function() {
     this.$.addPrinterDialog.open();
+    this.$.addPrinterErrorMessage.hidden = true;
   },
 });