Settings WebUI: add missing import for paper-progress in passwords export dialog

Bug: 897050
Change-Id: I0d3a758917d44ea9841e78696b1be829b20b3596
Reviewed-on: https://chromium-review.googlesource.com/c/1297636Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Esmael El-Moslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602223}

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

@@ -3,6 +3,7 @@
 <link rel="import" href="chrome://resources/cr_elements/cr_dialog/cr_dialog.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-progress/paper-progress.html">
 <link rel="import" href="../settings_shared_css.html">
 
 <dom-module id="passwords-export-dialog">