[CUPS] Implement the UI handler for adding a new printer.

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 {
+        background-color: black;
+        color: white;
+        font: 13px;
+        left: 150px;

[michaelpg, 2016/09/20 20:58:42]

you'll need to make this work in RTL, e.g.:

.message[dir=rtl] {
  left: 0;
  right: 150px;
}

you can test with a language like Arabic

[xdai1, 2016/09/21 17:40:19]

I could not test the exact string since it hasn't been translated so I used a
similar string and tested it. It looks fine to me (I made a screenshot here:
https://drive.google.com/corp/drive/u/0/folders/0B4R9nvLdzmC9d3o2WDNyNGRjejQ See
the back rectangle). Let me know if it looks good to you.

[michaelpg, 2016/09/21 19:13:23]

So the rectangle is centered horizontally at any width (when you resize the
page)?

[xdai1, 2016/09/21 23:16:16]

No, it's not... It's always centered horizontally against the full width of the
Cups print subpage. 

+        padding-bottom: 15px;
+        padding-top: 15px;
+        position: absolute;
+        text-align: center;
+        top: 550px;
+        width: 350px;
+      }
     </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 class="message" id="addPrinterMessage" hidden>
+      $i18n{printerAddedSuccessfulMessage}
+    </div>
   </template>
   <script src="cups_printers.js"></script>
 </dom-module>