[MD Bookmarks] Add UI for Material Bookmarks.

chrome/browser/resources/md_bookmarks/folder_node.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.
+
+Polymer({
+  is: 'bookmarks-folder-node',
+
+  properties: {
+    /** @type {BookmarkTreeNode} */
+    item: Object,
+
+    isSelected: {
+      type: Boolean,
+      value: false,
+      reflectToAttribute: true,
+    },
+  },
+
+  /**
+   * @private
+   * @return {string}
+   */
+  getFolderIcon_: function() {
+    //TODO(jiaxi): Move these icons to shared file.
+    return this.isSelected ? 'bookmarks:folder-open' : 'bookmarks:folder';
+  },
+
+  /**
+   * @private
+   * @return {string}
+   */
+  getArrowIcon_: function() {
+    //TODO(jiaxi): Move these icons to shared file.

[calamity, 2017/01/04 04:33:07]

// TODO


But also, these TODOs should really be in the icons.html.

[jiaxi, 2017/01/04 04:41:31]

Done.

+    return this.item.isOpen ? 'bookmarks:arrow-drop-up' :
+                              'bookmarks:arrow-drop-down';
+  },
+
+  /** @private */
+  selectFolder_: function() {
+    this.fire('selected-folder-changed', this.item.id);
+  },
+
+  /**
+   * Occurs when the drop down arrow is tapped.
+   * @private
+   */
+  toggleFolder_: function() {
+    this.fire('folder-open-changed', {
+      id: this.item.id,
+      open: !this.item.isOpen,
+    });
+  },
+
+  /**
+   * @private
+   * @return {boolean}
+   */
+  hasChildFolder_: function() {
+    for (var i = 0; i < this.item.children.length; i++) {
+      if (!this.item.children[i].url)
+        return true;
+    }
+    return false;
+  },
+});