Firefox overlay is seen opened even if Import Overlay is Cancelled.

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

 <link rel="import" href="chrome://resources/cr_elements/cr_dialog/cr_dialog.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/html/md_select_css.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-icon/iron-icon.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-spinner/paper-spinner.html">
 <link rel="import" href="../controls/settings_checkbox.html">
 <link rel="import" href="../controls/settings_toggle_button.html">
@@ skipping 16 matching lines @@
         margin: 0 8px;
       }
 
       #successIcon {
         fill: var(--paper-blue-600);
         height: 80px;
         margin: auto;
         width: 100%;
       }
     </style>
-    <dialog is="cr-dialog" id="dialog" close-text="$i18n{close}" ignore-popstate>
+    <dialog is="cr-dialog" id="dialog" close-text="$i18n{close}"
+        on-close="closeDialog_" ignore-popstate>
       <div class="title">$i18n{importTitle}</div>
       <div class="body">
         <div hidden$="[[!hasImportStatus_(
             importStatusEnum_.SUCCEEDED, importStatus_)]]">
           <iron-icon id="successIcon" icon="settings:check-circle">
           </iron-icon>
           <div hidden$="[[!prefs.import_dialog_bookmarks.value]]">
             <div class="description">$i18n{importSuccess}</div>
             <settings-toggle-button class="start"
                 label="$i18n{showBookmarksBar}"
@@ skipping 67 matching lines @@
 
         <paper-button id="done" class="action-button"
             hidden$="[[!hasImportStatus_(
                 importStatusEnum_.SUCCEEDED, importStatus_)]]"
             on-tap="closeDialog_">$i18n{done}</paper-button>
       </div>
     </dialog>
   </template>
   <script src="import_data_dialog.js"></script>
 </dom-module>