MD Bookmarks: Add right-click context menu to sidebar folders

chrome/test/data/webui/md_bookmarks/folder_node_test.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.
 
 suite('<bookmarks-folder-node>', function() {
   var rootNode;
   var store;
 
   function getFolderNode(id) {
     return findFolderNode(rootNode, id);
@@ skipping 113 matching lines @@
     assertEquals('3', getNextChild('2', '4', true).itemId);
     assertEquals('4', getNextChild('0', '7', true).itemId);
 
     // Skips closed folders.
     store.data.closedFolders = new Set('2');
     store.notifyObservers();
 
     assertEquals(null, getNextChild('1', '2', false));
     assertEquals('2', getNextChild('0', '7', true).itemId);
   });
+
+  test('right click opens context menu', function() {
+    var commandManager = new TestCommandManager();
+    document.body.appendChild(commandManager);
+
+    var node = getFolderNode('2');
+    node.$.container.dispatchEvent(new MouseEvent('contextmenu'));
+
+    assertDeepEquals(bookmarks.actions.selectFolder('2'), store.lastAction);
+    commandManager.assertMenuOpenForIds(['2']);
+  });
 });