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

chrome/browser/resources/settings/passwords_and_forms_page/passwords_and_forms_page.html

 <link rel="import" href="chrome://resources/html/assert.html">
 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
+<link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout-classes.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="autofill_section.html">
 <link rel="import" href="passwords_section.html">
 <link rel="import" href="../controls/extension_controlled_indicator.html">
 <link rel="import" href="../controls/settings_toggle_button.html">
 <link rel="import" href="../prefs/prefs.html">
 <link rel="import" href="../prefs/prefs_behavior.html">
 <link rel="import" href="../route.html">
 <link rel="import" href="../settings_page/settings_animated_pages.html">
 <link rel="import" href="../settings_page/settings_subpage.html">
 <link rel="import" href="../settings_shared_css.html">
 
 <dom-module id="settings-passwords-and-forms-page">
   <template>
-    <style include="settings-shared"></style>
+    <style include="settings-shared iron-flex"></style>
     <settings-animated-pages id="pages" section="passwordsAndForms"
         focus-config="[[focusConfig_]]">
       <neon-animatable route-path="default">
         <div class="settings-box first two-line">
           <div class="start two-line" on-tap="onAutofillTap_" actionable
               id="autofillManagerButton">
             <div class="flex">
               $i18n{autofill}
               <div class="secondary" id="autofillSecondary">
                 $i18n{autofillDetail}
@@ skipping 36 matching lines @@
             search-term="{{passwordFilter_}}">
           <passwords-section id="passwordSection" filter="[[passwordFilter_]]"
               prefs="{{prefs}}">
           </passwords-section>
         </settings-subpage>
       </template>
     </settings-animated-pages>
   </template>
   <script src="passwords_and_forms_page.js"></script>
 </dom-module>