MD Settings: Remove usage of deprecated iron-flex-layout.html.

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

 <link rel="import" href="chrome://resources/html/util.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>
+    <style include="settings-shared">
+      .block {
+        display: block;
+      }
+    </style>
     <div class="settings-box first two-line">
       <div class="start">
         <div>$i18n{downloadLocation}</div>
         <div class="secondary" no-search>
 <if expr="not chromeos">
           [[prefs.download.default_directory.value]]
 </if>
 <if expr="chromeos">
           [[getDownloadLocation_(prefs.download.default_directory.value)]]
 </if>
@@ skipping 30 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>