MD User manager: Migrate from PaperDialogBehavior to cr-dialog.

chrome/browser/resources/md_user_manager/user_manager_dialog.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.
-
-/**
- * @fileoverview 'user-manager-dialog' is a modal dialog for the user manager.
- */
-Polymer({
-  is: 'user-manager-dialog',
-
-  behaviors: [Polymer.PaperDialogBehavior],
-
-  properties: {
-    /** @override */
-    noCancelOnOutsideClick: {type: Boolean, value: true},
-
-    /** @override */
-    withBackdrop: {type: Boolean, value: true},
-
-    /**
-     * The first node that can receive focus.
-     * @type {!Node}
-     */
-    firstFocusableNode: {
-      type: Object,
-      value: function() {
-        return this.$.close;
-      },
-      observer: 'firstFocusableNodeChanged_'
-    },
-
-    /**
-     * The last node that can receive focus.
-     * @type {!Node}
-     */
-    lastFocusableNode: {
-      type: Object,
-      value: function() {
-        return this.$.close;
-      },
-      observer: 'lastFocusableNodeChanged_'
-    }
-  },
-
-  /**
-   * Returns the first and the last focusable elements in order to wrap the
-   * focus for the dialog in Polymer.PaperDialogBehavior.
-   * @override
-   * @type {!Array<!Node>}
-   */
-  get _focusableNodes() {
-    return [this.firstFocusableNode, this.lastFocusableNode];
-  },
-
-  /**
-   * Observer for firstFocusableNode. Updates __firstFocusableNode in
-   * Polymer.PaperDialogBehavior.
-   */
-  firstFocusableNodeChanged_: function(newValue) {
-    this.__firstFocusableNode = newValue;
-  },
-
-  /**
-   * Observer for lastFocusableNodeChanged_. Updates __lastFocusableNode in
-   * Polymer.PaperDialogBehavior.
-   */
-  lastFocusableNodeChanged_: function(newValue) {
-    this.__lastFocusableNode = newValue;
-  }
-});