Migrate <cr-dialog> from PaperDialogBehavior to native <dialog>.

ui/webui/resources/cr_elements/cr_dialog/cr_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 'cr-dialog' is a component for showing a modal dialog.
+ * @fileoverview 'cr-dialog' is a component for showing a modal dialog. If the
+ * dialog is closed via close(), a 'close' event is fired. If the dialog is
+ * canceled via cancel(), a 'cancel' event is fired followed by a 'close' event.
+ * Additionally clients can inspect the dialog's |returnValue| property inside
+ * the 'close' event listener to determine whether it was canceled or just
+ * closed, where a truthy value means success, and a falsy value means it was
+ * canceled.
  */
 Polymer({
   is: 'cr-dialog',
+  extends: 'dialog',
 
-  properties: {
-    /** @override */
-    noCancelOnOutsideClick: {
-      type: Boolean,
-      value: true,
-    },
-
-    /** @override */
-    noCancelOnEscKey: {
-      type: Boolean,
-      value: false,
-    },
-
-    /**
-     * @type {!Element}
-     * @override
-     */
-    sizingTarget: {
-      type: Element,
-      value: function() {
-        return assert(this.$$('.body-container'));
-      },
-    },
-
-    /** @override */
-    withBackdrop: {
-      type: Boolean,
-      value: true,
-    },
+  cancel: function() {
+    this.fire('cancel');
+    HTMLDialogElement.prototype.close.call(this, '');
   },
 
-  behaviors: [Polymer.PaperDialogBehavior],
+  /**
+   * @param {string=} opt_returnValue
+   * @override
+   */
+  close: function(opt_returnValue) {
+    HTMLDialogElement.prototype.close.call(this, 'success');
+  },
 
   /** @return {!PaperIconButtonElement} */
   getCloseButton: function() {
     return this.$.close;
   },
 });