Fix UserManagerBrowserTest

chrome/test/data/webui/md_user_manager/import_supervised_user_tests.js

Index: chrome/test/data/webui/md_user_manager/import_supervised_user_tests.js
diff --git a/chrome/test/data/webui/md_user_manager/import_supervised_user_tests.js b/chrome/test/data/webui/md_user_manager/import_supervised_user_tests.js
index 4e3f23e759d386ea29ff3a903bba17e8c761619c..fe1321c32ff6a0d145472fbe720dd0b3367d3c46 100644
--- a/chrome/test/data/webui/md_user_manager/import_supervised_user_tests.js
+++ b/chrome/test/data/webui/md_user_manager/import_supervised_user_tests.js
@@ -25,7 +25,11 @@ cr.define('user_manager.import_supervised_user_tests', function() {
         Polymer.dom.flush();
       });
 
-      teardown(function() { importElement.remove(); });
+      teardown(function(done) {
+        importElement.remove();
+        // Allow asynchronous tasks to finish.
+        setTimeout(done);
+      });
 
       test('Dialog does not show if no signed-in user is provided', function() {
         // The dialog is initially not visible.