[MD Bookmarks] Add toasts.

chrome/test/data/webui/md_bookmarks/toast_manager_test.js

+// Copyright 2017 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.
+
+suite('<bookmarks-toast-manager>', function() {
+  var toastManager;
+  var store;
+
+  setup(function() {
+    toastManager = document.createElement('bookmarks-toast-manager');
+    replaceBody(toastManager);
+  });
+
+  test('simple show/hide', function() {

[dpapad, 2017/06/01 17:35:44]

The test claims to test show/hide, but only toastManager.show() is called. Can
we add additional assertions for hide?

[calamity, 2017/06/02 05:34:22]

Done.

+    toastManager.show('test', false);
+    var toast = toastManager.$.toast;
+    assertTrue(toast.open);
+    assertEquals('test', toastManager.$.content.textContent);
+    assertTrue(toastManager.$$('paper-button').hidden);
+
+    toastManager.show('test', true);
+    assertFalse(toastManager.$$('paper-button').hidden);
+  });
+});