MD Settings: label and describe a bunch of subpage/open-in-new buttons

chrome/browser/resources/settings/a11y_page/a11y_page.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="../settings_shared_css.html">
 
 <if expr="chromeos">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-toggle-button/paper-toggle-button.html">
 <link rel="import" href="manage_a11y_page.html">
 <link rel="import" href="../settings_page/settings_animated_pages.html">
@@ skipping 11 matching lines @@
           <div class="start">$i18n{optionsInMenuLabel}</div>
           <paper-toggle-button id="optionsInMenuToggle"
               checked="{{prefs.settings.a11y.enable_menu.value}}">
           </paper-toggle-button>
         </div>
         <template is="dom-if" if="[[!isGuest_]]">
           <div id="subpage-trigger" class="settings-box two-line"
               on-tap="onManageAccessibilityFeaturesTap_" actionable>
             <div class="start">
               $i18n{manageAccessibilityFeatures}
-              <div class="secondary">$i18n{moreFeaturesLinkDescription}</div>
+              <div class="secondary" id="themesSecondary">
+                $i18n{moreFeaturesLinkDescription}
+              </div>
             </div>
-            <button class="subpage-arrow" is="paper-icon-button-light"></button>
+            <button class="subpage-arrow" is="paper-icon-button-light"
+                aria-label="$i18n{manageAccessibilityFeatures}"
+                aria-describedby="themesSecondary"></button>
           </div>
         </template>
       </neon-animatable>
 
       <template is="dom-if" route-path="/manageAccessibility">
         <settings-subpage
             associated-control="[[$$('#subpage-trigger')]]"
             page-title="$i18n{manageAccessibilityFeatures}">
           <settings-manage-a11y-page prefs="{{prefs}}">
           </settings-manage-a11y-page>
         </settings-subpage>
       </template>
     </settings-animated-pages>
 </if>
 
 <if expr="not chromeos">
     <div class="settings-box first two-line" on-tap="onMoreFeaturesTap_"
         actionable>
       <div class="start">
         $i18n{moreFeaturesLink}
-        <div class="secondary">$i18n{a11yWebStore}</div>
+        <div class="secondary" id="moreFeaturesSecondary">
+          $i18n{a11yWebStore}
+        </div>
       </div>
-      <button class="icon-external" is="paper-icon-button-light"></button>
+      <button class="icon-external" is="paper-icon-button-light"
+          aria-label="$i18n{moreFeaturesLink}"
+          aria-describedby="moreFeaturesSecondary"></button>
     </div>
 </if>
 
   </template>
   <script src="a11y_page.js"></script>
 </dom-module>