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

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

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="/printing_page/cups_add_printer_dialog.html">
 <link rel="import" href="/printing_page/cups_printers_list.html">
 <link rel="import" href="/settings_shared_css.html">
 
 <dom-module id="settings-cups-printers">
   <template>
     <style include="settings-shared">
       a[is='action-link'] {
         display: inline-block;
         text-decoration: none;
       }
 
       a[is='action-link']:hover {
         color: blue;
         text-decoration: underline;
       }
-      
+
       #message {
         display: flex;
         justify-content: center;
         position: absolute;
         top: 85%;
         width: 100%;
       }
 
       .center {
         background-color: black;
         color: white;
         font: 13px;
         padding-bottom: 15px;
         padding-top: 15px;
         text-align: center;
         width: 350px;
       }
+
+      #addPrinterErrorMessage {
+        display: flex;
+        justify-content: space-around;
+      }
+
+      #addPrinterErrorMessage a[is='action-link'] {
+        text-transform: uppercase;
+      }
     </style>
 
     <div class="settings-box first">
       <a is="action-link" on-tap="onAddPrinterTap_" actionable>
         $i18n{addCupsPrinter}
       </a>
     </div>
 
     <settings-cups-add-printer-dialog id="addPrinterDialog">
     </settings-cups-add-printer-dialog>
 
     <settings-cups-printers-list printers="{{printers}}"
         search-term="[[searchTerm]]">
     </settings-cups-printers-list>
 
     <div id="message">
-      <div class="center" id="addPrinterMessage" hidden>
+      <div class="center" id="addPrinterDoneMessage" hidden>
         $i18n{printerAddedSuccessfulMessage}
       </div>
+      <div class="center" id="addPrinterErrorMessage" hidden>
+        <span>$i18n{printerAddedFailedMessage}</span>
+        <a is="action-link" on-tap="onAddPrinterTap_" actionable>
+          $i18n{printerAddedTryAgainMessage}
+        </a>
+      </div>
     </div>
   </template>
   <script src="cups_printers.js"></script>
 </dom-module>