WebUI: swap paper-dropdown-menu out for md-select.

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

 <link rel="import" href="chrome://resources/html/polymer.html">
 
 <link rel="import" href="chrome://resources/html/md_select_css.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-input/paper-input.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-spinner/paper-spinner.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="cups_add_printer_dialog_util.html">
 <link rel="import" href="cups_printers_browser_proxy.html">
@@ skipping 87 matching lines @@
 
       .settings-box.two-line {
         min-height: 72px;
       }
 
       .settings-box .start .label {
         color: var(--google-grey-700);
       }
 
       .md-select {
-        width: calc(270px + var(--md-side-padding));
+        width: calc(270px + var(--md-select-side-padding));
       }
 
       .md-select-underline {
         -webkit-margin-start: 0;
       }
 
       paper-input {
         --paper-input-container-color: var(--paper-grey-600);
         --paper-input-container-input: {
           font-size: inherit;
@@ skipping 278 matching lines @@
     <!-- Manufacturer and Model Dialog -->
     <template is="dom-if" if="[[showManufacturerDialog_]]" restamp>
       <add-printer-manufacturer-model-dialog new-printer="{{newPrinter}}"
           setup-failed="[[setupFailed]]">
       </add-printer-manufacturer-model-dialog>
     </template>
 
   </template>
   <script src="cups_add_printer_dialog.js"></script>
 </dom-module>