MD Settings: Don't auto-close navigable dialogs on popstate.

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

 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/html/icon.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/neon-animation/neon-animatable.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-checkbox/paper-checkbox.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_dialog/cr_dialog.html">
@@ skipping 296 matching lines @@
             associated-control="[[$$('#picture-subpage-trigger')]]"
             page-title="$i18n{editPerson}">
           <settings-manage-profile profile-icon-url="[[profileIconUrl_]]"
               profile-name="[[profileName_]]" sync-status="[[syncStatus]]">
           </settings-manage-profile>
         </settings-subpage>
       </template>
 </if>
     </settings-animated-pages>
 
-    <dialog is="cr-dialog" id="disconnectDialog" on-close="onDisconnectClosed_">
+    <dialog is="cr-dialog" id="disconnectDialog" on-close="onDisconnectClosed_"
+        ignore-popstate>
       <div class="title">$i18n{syncDisconnectTitle}</div>
       <div class="body">
         <div inner-h-t-m-l="[[getDisconnectExplanationHtml_(syncStatus.domain)]]">
         </div>
   <if expr="(not chromeos and is_posix) or is_win or is_macosx">
         <paper-checkbox id="deleteProfile" hidden=[[syncStatus.domain]]>
           $i18n{syncDisconnectDeleteProfile}
         </paper-checkbox>
   </if>
       </div>
@@ skipping 14 matching lines @@
 
 <if expr="chromeos">
     <template is="dom-if" if="[[easyUnlockEnabled_]]">
       <easy-unlock-turn-off-dialog id="easyUnlockTurnOffDialog">
       </easy-unlock-turn-off-dialog>
     </template>
 </if>
   </template>
   <script src="people_page.js"></script>
 </dom-module>