MD Bookmarks: Implement basis for new data-binding system

chrome/browser/resources/md_bookmarks/reducers.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 Module of functions which produce a new page state in response
+ * to an action. Reducers (in the same sense as Array.prototype.reduce) must be
+ * pure functions: they must not modify existing state objects, or make any API
+ * calls.
+ */
+
+cr.define('bookmarks', function() {
+  /**
+   * Root reducer for the Bookmarks page. This is called by the store in
+   * response to an action, and the return value is used to update the UI.
+   * @param {!BookmarksPageState} state
+   * @param {Action} action
+   * @return {!BookmarksPageState}
+   */
+  function reduceAction(state, action) {
+    return {};
+  }
+
+  return {
+    reduceAction: reduceAction,
+  };
+});