MD Bookmarks: Prevent flash of folder contents when changing search term

chrome/browser/resources/md_bookmarks/types.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.
 
 /**
  * @fileoverview Closure typedefs for MD Bookmarks.
  */
 
 /**
  * A normalized version of chrome.bookmarks.BookmarkTreeNode.
@@ skipping 19 matching lines @@
  * @typedef {{
  *   items: !Set<string>,
  *   anchor: ?string,
  * }}
  *
  * |items| is used as a set and all values in the map are true.
  */
 var SelectionState;
 
 /**
+ * Note:
+ * - If |results| is null, it means no search results have been returned. This
+ *   is different to |results| being [], which means the last search returned 0
+ *   results.
+ * - |term| is the last search that was performed by the user, and |results| are
+ *   the last results that were returned from the backend. We don't clear
+ *   |results| on incremental searches, meaning that |results| can be 'stale'
+ *   data from a previous search term (while |inProgress| is true). If you need
+ *   to know the exact search term used to generate |results|, you'll need to
+ *   add a new field to the state to track it (eg, SearchState.resultsTerm).
  * @typedef {{
  *   term: string,
  *   inProgress: boolean,
- *   results: !Array<string>,
+ *   results: ?Array<string>,
  * }}
  */
 var SearchState;
 
 /** @typedef {!Set<string>} */
 var ClosedFolderState;
 
 /**
  * @typedef {{
  *   canEdit: boolean,
@@ skipping 41 matching lines @@
 
   /** @type {boolean} */
   this.sameProfile = false;
 }
 
 /** @interface */
 function StoreObserver() {}
 
 /** @param {!BookmarksPageState} newState */
 StoreObserver.prototype.onStateChanged = function(newState) {};