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

chrome/browser/resources/settings/people_page/import_data_browser_proxy.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview A helper object used from the the Import Data dialog to allow
  * users to import data (like bookmarks) from other web browsers.
  */
 cr.exportPath('settings');
 
@@ skipping 38 matching lines @@
      * Starts importing data for the specificed source browser profile. The C++
      * responds with the 'import-data-status-changed' WebUIListener event.
      * @param {number} sourceBrowserProfileIndex
      */
     importData: function(sourceBrowserProfileIndex) {},
 
     /**
      * Prompts the user to choose a bookmarks file to import bookmarks from.
      */
     importFromBookmarksFile: function() {},
+    
+    /**
+     * Close the import lock dialog if it is opened.
+     */
+    closeImportLockDialog: function() {},
   };
 
   /**
    * @constructor
    * @implements {settings.ImportDataBrowserProxy}
    */
   function ImportDataBrowserProxyImpl() {}
   // The singleton instance_ is replaced with a test version of this wrapper
   // during testing.
   cr.addSingletonGetter(ImportDataBrowserProxyImpl);
 
   ImportDataBrowserProxyImpl.prototype = {
     /** @override */
     initializeImportDialog: function() {
       return cr.sendWithPromise('initializeImportDialog');
     },
 
     /** @override */
     importData: function(sourceBrowserProfileIndex) {
       chrome.send('importData', [sourceBrowserProfileIndex]);
     },
 
     /** @override */
     importFromBookmarksFile: function() {
       chrome.send('importFromBookmarksFile');
     },
+
+    /** @override */
+    closeImportLockDialog: function() {
+      chrome.send('closeImportLockDialog');
+    },
   };
 
   return {
     ImportDataBrowserProxy: ImportDataBrowserProxy,
     ImportDataBrowserProxyImpl: ImportDataBrowserProxyImpl,
   };
 });