[MD settings] layout sub-headers in display settings

chrome/browser/resources/settings/device_page/display.html

 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-flex-layout.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-checkbox/paper-checkbox.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-dropdown-menu/paper-dropdown-menu.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-listbox/paper-listbox.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-slider/paper-slider.html">
 <link rel="import" href="/device_page/display_layout.html">
 <link rel="import" href="/device_page/display_overscan_dialog.html">
 <link rel="import" href="/settings_shared_css.html">
 
 <dom-module id="settings-display">
   <template>
     <style include="settings-shared">
-     .display-section {
-       align-self: flex-start;
-       font-size: 100%;
-       font-weight: 500;
-       margin: 10px 0;
-     }
-
      .settings-box.embedded {
        align-self: stretch;
        margin-left: 20px;
        padding: 0;
      }
 
      display-layout {
        align-self: stretch;
        flex: 1 1;
        height: 300px;
        margin: 10px;
      }
 
      .textarea {
        margin: 10px 0;
      }
 
      .info-text {
        color: var(--paper-grey-500);
        margin-top: 5px;
      }
 
      .settings-box > paper-button:first-child {
        padding-left: 0
      }
     </style>
     <div class="settings-box first layout vertical self-stretch">
-      <div class="display-section">$i18n{displayArrangement}</div>
+      <h2>$i18n{displayArrangement}</h2>
       <display-layout id="displayLayout"
           selected-display="[[selectedDisplay]]"
           on-select-display="onSelectDisplay_">
       </display-layout>
     </div>
-    <div class="settings-box layout vertical">
-      <div class="display-section">[[selectedDisplay.name]]</div>
+    <div class="settings-box layout vertical first">
+      <h2>[[selectedDisplay.name]]</h2>
       <div class="settings-box embedded first">
         <paper-checkbox class="flex" checked="[[isMirrored_(displays)]]"
             hidden$="[[!showMirror_(displays)]]" on-tap="onMirroredTap_">
           $i18n{displayMirror}
         </paper-checkbox>
         <paper-button
             hidden$="[[!showMakePrimary_(selectedDisplay, primaryDisplayId)]]"
             on-tap="onMakePrimaryTap_">
           $i18n{displayMakePrimary}
         </paper-button>
@@ skipping 38 matching lines @@
       </div>
 
       <settings-display-overscan-dialog id="displayOverscan"
           display-id="{{overscanDisplayId}}">
       </settings-display-overscan-dialog>
 
     </div>
   </template>
   <script src="display.js"></script>
 </dom-module>