MD Settings: clean up text controls (links, buttons)

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

 <link rel="import" href="chrome://resources/html/action_link.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="/controls/settings_toggle_button.html">
 <link rel="import" href="/settings_shared_css.html">
 
 <dom-module id="settings-stylus">
   <template>
     <style include="settings-shared"></style>
 
     <div class="settings-box">
       <settings-toggle-button class="start"
           pref="{{prefs.settings.enable_stylus_tools}}"
           label="$i18n{stylusEnableStylusTools}">
       </settings-toggle-button>
     </div>
 
     <div class="settings-box continuation">
       <settings-toggle-button class="start"
           pref="{{prefs.settings.launch_palette_on_eject_event}}"
           label="$i18n{stylusAutoOpenStylusTools}"
           disabled="[[!prefs.settings.enable_stylus_tools.value]]">
       </settings-toggle-button>
     </div>
 
+    <!-- TODO(scottchen): Make a proper a[href].settings-box with

[michaelpg, 2017/01/23 06:51:19]

this is hard to understand, can you include a crbug.com link?

[scottchen, 2017/01/23 18:49:07]

Done.

+         icon-external -->
     <div class="settings-box">
       <!-- TODO(jdufault): This should launch an intent (using the
         enable-intent-picker flag) that opens up the play store to a curated
         list of apps. -->
-      <a is="action-link" target="_blank"
+      <a target="_blank"
          href="https://play.google.com/store/apps/collection/promotion_30023cb_stylus_apps">
         $i18n{stylusFindMoreApps}
       </a>
     </div>
 
   </template>
   <script src="stylus.js"></script>
 </dom-module>