[MD settings] expand subpages to 100%

chrome/browser/resources/settings/basic_page/basic_page.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="../a11y_page/a11y_page.html">
 <link rel="import" href="../appearance_page/appearance_page.html">
 <link rel="import" href="../controls/settings_idle_render.html">
 <link rel="import" href="../downloads_page/downloads_page.html">
 <link rel="import" href="../languages_page/languages_page.html">
 <link rel="import" href="../on_startup_page/on_startup_page.html">
 <link rel="import" href="../passwords_and_forms_page/passwords_and_forms_page.html">
 <link rel="import" href="../people_page/people_page.html">
 <link rel="import" href="../printing_page/printing_page.html">
@@ skipping 132 matching lines @@
         <template is="dom-if" if="[[showPage(pageVisibility.onStartup)]]"
             restamp>
           <settings-section page-title="$i18n{onStartup}" section="onStartup">
             <settings-on-startup-page prefs="{{prefs}}">
             </settings-on-startup-page>
           </settings-section>
         </template>
       </div>
     </template>
 
-    <div hidden$="[[!showAdvancedSettings_(pageVisibility.advancedSettings)]]">
+    <template is="dom-if" if="[[showAdvancedSettings_(pageVisibility.advancedSettings)]]">
       <template is="dom-if" if="[[showAdvancedToggle_(
           inSearchMode, hasExpandedSection_)]]">
         <div id="toggleSpacer"></div>
         <h2 id="toggleContainer">
           <paper-button id="advancedToggle" active="{{advancedToggleExpanded}}"
               aria-active-attribute="aria-expanded" toggles>
             <span>$i18n{advancedPageTitle}</span>
             <iron-icon icon="[[getArrowIcon_(advancedToggleExpanded)]]">
             </iron-icon>
           </paper-button>
@@ skipping 74 matching lines @@
 </if>
           <template is="dom-if" if="[[showPage(pageVisibility.reset)]]"
               restamp>
             <settings-section page-title="$i18n{resetPageTitle}"
                 section="reset">
               <settings-reset-page></settings-reset-page>
             </settings-section>
           </template>
         </div>
       </template>
-    </div>
+    </template>
   </template>
   <script src="basic_page.js"></script>
 </dom-module>