MD Settings: add an aria-label to control indicators (often policy)

chrome/browser/resources/settings/downloads_page/downloads_page.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-flex-layout.html">
 <link rel="import" href="../controls/controlled_button.html">
 <link rel="import" href="../controls/settings_toggle_button.html">
 <link rel="import" href="../settings_shared_css.html">
 <link rel="import" href="downloads_browser_proxy.html">
 
 <dom-module id="settings-downloads-page">
   <template>
     <style include="settings-shared"></style>
     <div class="settings-box first two-line">
       <div class="start">
         <div>$i18n{downloadLocation}</div>
         <div class="secondary">
 <if expr="not chromeos">
           [[prefs.download.default_directory.value]]
 </if>
 <if expr="chromeos">
           [[getDownloadLocation_(prefs.download.default_directory.value)]]
 </if>
         </div>
       </div>
       <div class="secondary-action">
         <controlled-button class="secondary-button" id="changeDownloadsPath"
+            label="$i18n{changeDownloadLocation}"
             on-tap="selectDownloadLocation_"
             pref="[[prefs.download.default_directory]]"
             end-justified>
-          $i18n{changeDownloadLocation}
         </controlled-button>
       </div>
     </div>
     <div class="settings-box block">
       <settings-toggle-button
           pref="{{prefs.download.prompt_for_download}}"
           label="$i18n{promptForDownload}">
       </settings-toggle-button>
 <if expr="chromeos">
       <settings-toggle-button
@@ skipping 12 matching lines @@
           <paper-button id="resetAutoOpenFileTypes" class="secondary-button"
               on-tap="onClearAutoOpenFileTypesTap_">
             $i18n{clear}
           </paper-button>
         </div>
       </div>
     </template>
   </template>
   <script src="downloads_page.js"></script>
 </dom-module>