MD Bookmarks: Enable the delete button in the toolbar overlay

chrome/test/data/webui/md_bookmarks/toolbar_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-toolbar>', function() {
   var toolbar;
   var store;
+  var commandManager;
 
   setup(function() {
     store = new bookmarks.TestStore({
       nodes: testTree(createFolder('1', [
         createItem('2'),
         createItem('3'),
       ])),
       selection: {
         items: new Set(),
         anchor: null,
       },
     });
     bookmarks.Store.instance_ = store;
 
     toolbar = document.createElement('bookmarks-toolbar');
     replaceBody(toolbar);
+
+    commandManager = new TestCommandManager();

[calamity, 2017/05/23 03:42:55]

Does this also need to get assigned to bookmarks.CommandManager.instance_? It
might be worth putting it in the TestCommandManager() constructor, or at least a
method (e.g HijackSingleton()).

Same with TestStore. 

[tsergeant, 2017/05/23 04:11:36]

CommandManager is a bit weird, because it takes over the singleton for itself
during attached:
https://cs.chromium.org/chromium/src/chrome/browser/resources/md_bookmarks/co...

That means that appending it to the body (and removing it during cleanup) will
automatically take care of the singleton.

However, I don't think we want to do this in the constructor automatically, in
case the test is doing something careful with the body.

Do you agree? Do you still want me to change TestStore anyway?

[calamity, 2017/05/23 05:34:19]

Oh yeah, I totally forgot about that subtlety.
We can defer this I think.

+    document.body.appendChild(commandManager);
   });
 
   test('selecting multiple items shows toolbar overlay', function() {
     assertFalse(toolbar.showSelectionOverlay);
 
     store.data.selection.items = new Set(['2']);
     store.notifyObservers();
     assertFalse(toolbar.showSelectionOverlay);
 
     store.data.selection.items = new Set(['2', '3']);
     store.notifyObservers();
     assertTrue(toolbar.showSelectionOverlay);
   });
+
+  test('clicking overlay delete button triggers a delete command', function() {
+    store.data.selection.items = new Set(['2', '3']);
+    store.notifyObservers();
+
+    Polymer.dom.flush();
+    MockInteractions.tap(
+        toolbar.$$('cr-toolbar-selection-overlay').deleteButton);
+
+    commandManager.assertLastCommand(Command.DELETE, ['2', '3']);
+  });
 });