Move settings-section animations into setting-section, make better

chrome/browser/resources/settings/animation/animation_group.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.
+
+cr.define('settings.animation', function() {
+  'use strict';
+
+  /**
+   * An AnimationGroup manages a set of animations, handles any styling setup or
+   * cleanup, and provides a Promise for chaining actions on finish or cancel.
+   * This abstracts out all these details so UI elements can simply create an
+   * object rather than individually track the state of every element, style and
+   * web animation. AnimationGroups may compose web animations and other
+   * AnimationGroups.
+   * @interface
+   */
+  function AnimationGroup() {}
+
+  AnimationGroup.prototype = {
+    /**
+     * Sets up and plays the animation(s).
+     * @return {!Promise} Convenient reference to |finished| for chaining.
+     */
+    play: assertNotReached,
+
+    /**
+     * If animations are still playing, immediately finishes them and resolves
+     * |finished|.
+     */
+    finish: assertNotReached,
+
+    /**
+     * If animations are still playing, immediately cancels them and rejects
+     * |finished|.
+     */
+    cancel: assertNotReached,
+
+    /**
+     * Resolved or rejected when the the AnimationGroup finishes or is canceled.
+     * @type {?Promise}
+     */
+    finished: null,
+  };
+
+  return {
+    AnimationGroup: AnimationGroup,
+  };
+});