MD Settings: adjust dialog style and scroll border visual

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

 <link rel="import" href="chrome://resources/cr_elements/cr_dialog/cr_dialog.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-dropdown/iron-dropdown.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-input/iron-input.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-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-input/paper-input-container.html">
 <link rel="import" href="cups_printers_browser_proxy.html">
 <link rel="import" href="../settings_shared_css.html">
@@ skipping 88 matching lines @@
 <dom-module id="add-printer-dialog">
   <template>
     <style include="settings-shared">
       #dialog .body {
         -webkit-padding-end: 0;
         -webkit-padding-start: 0;
         height: 350px;
       }
 
       #dialog .button-container {
-        border-top: 1px solid rgba(0, 0, 0, 0.14);
-        margin-top: 0;
-        padding-top: 10px;
-      }
-
-      #dialog .button-container ::content paper-button {
-        font-size: 107.69%;  /* 14px / 13px */
-        font-weight: bold;
+        border-top: 1px solid var(--paper-grey-300);
       }
     </style>
 
     <dialog is="cr-dialog" id="dialog" close-text="$i18n{close}">
       <div class="title">
         <content select=".dialog-title"></content>
       </div>
       <div class="body">
         <content select=".dialog-body"></content>
       </div>
       <div class="button-container">
         <content select=".dialog-buttons"></content>
       </div>
     </dialog>
   </template>
   <script src="cups_add_printer_dialog_util.js"></script>
 </dom-module>