[MD Bookmarks] Add Select for Bookmarks.

chrome/test/data/webui/md_bookmarks/item_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-item>', function() {
   var item;
   var TEST_ITEM = createItem('0');
 
   setup(function() {
     item = document.createElement('bookmarks-item');
     replaceBody(item);
     item.item = TEST_ITEM;
   });
 
   test('changing the url changes the favicon', function() {
     var favicon = item.$.icon.style.backgroundImage;
     item.set('item.url', 'http://www.mail.google.com');
     assertNotEquals(favicon, item.$.icon.style.backgroundImage);
   });
 
   test('changing isFolder_ hides/unhides the folder/icon', function() {
     item.isFolder_ = true;
     assertFalse(item.$['folder-icon'].hidden);
     assertTrue(item.$.icon.hidden);
 
     item.isFolder_ = false;
     assertTrue(item.$['folder-icon'].hidden);
     assertFalse(item.$.icon.hidden);
   });
+
+  test('pressing the buttons fires the right event', function() {
+    var shiftEventCount = 0;
+    var ctrlEventCount = 0;
+    var normalEventCount = 0;
+
+    document.addEventListener('select-single-item', function() {
+      normalEventCount++;
+    });
+    MockInteractions.tap(item);
+    assertEquals(1, normalEventCount);
+
+    document.addEventListener('shift-select-multiple-items', function() {
+      shiftEventCount++;
+    });
+    customClick(item, {shiftKey: true});
+    assertEquals(1, normalEventCount);
+    assertEquals(1, shiftEventCount);
+
+    document.addEventListener('ctrl-select-multiple-items', function() {
+      ctrlEventCount++;
+    });

[calamity, 2017/01/17 06:12:22]

Add all 3 event listeners at the beginning and assert for all values each time.
Consider that the 'single-select-item' action might trigger all the other event
listeners. That wouldn't get caught by this test.

You can use map to make this a little nicer (check comment in other test).

[jiaxi, 2017/01/20 04:51:09]

Done.

+    customClick(item, {ctrlKey: true});
+    assertEquals(1, normalEventCount);
+    assertEquals(1, shiftEventCount);
+    assertEquals(1, ctrlEventCount);
+  });
 });