MD Settings: Fix sync page layout after removing iron-flex-layout.html usage.

chrome/browser/resources/settings/people_page/sync_page.html

 <link rel="import" href="chrome://resources/html/i18n_behavior.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-a11y-keys/iron-a11y-keys.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/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-toggle-button/paper-toggle-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-input/paper-input.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-radio-button/paper-radio-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-radio-group/paper-radio-group.html">
 <link rel="import" href="sync_browser_proxy.html">
 <link rel="import" href="../route.html">
 <link rel="import" href="../settings_shared_css.html">
 
 <dom-module id="settings-sync-page">
   <template>
-    <style include="settings-shared">
+    <style include="settings-shared iron-flex">
       #create-password-box,
       #reset-sync-message-box {
         /* In order to line up with the encryption radio box text. */
         -webkit-margin-start: var(--settings-indent-width);
       }
 
       paper-input {
         width: var(--paper-input-max-width);
         --paper-input-container-focus-color: var(--google-blue-500);
         --paper-input-container-input: {
@@ skipping 304 matching lines @@
                                                          confirmation_)]]">
               $i18n{save}
             </paper-button>
           </div>
         </div>
       </template>
     </div>
   </template>
   <script src="sync_page.js"></script>
 </dom-module>