MD Settings: Make subpage extend to bottom of page with no overscroll

chrome/browser/resources/settings/settings_main/settings_main.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/html/promise_resolver.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="../about_page/about_page.html">
 <link rel="import" href="../basic_page/basic_page.html">
 <link rel="import" href="../route.html">
 <link rel="import" href="../settings_vars_css.html">
 
 <dom-module id="settings-main">
   <template>
     <style>
       #overscroll {
         margin-top: 64px;
       }
 
+      .showing-subpage ~ #overscroll {
+        display: none;
+      }
+
       #noSearchResults {
         align-items: center;
         display: flex;
         flex-direction: column;
         margin-top: 80px;
       }
 
       #noSearchResults div:first-child {
         font-size: 120%;
         margin-bottom: 10px;
@@ skipping 15 matching lines @@
     </template>
     <template is="dom-if" if="[[showPages_.about]]">
       <settings-about-page in-search-mode="[[inSearchMode_]]">
       </settings-about-page>
     </template>
     <div id="overscroll" style="padding-bottom: [[overscroll_]]px"></div>
   </template>
   <script src="settings_main.js"></script>
   <script src="../search_settings.js"></script>
 </dom-module>