MD Settings: fix overflow scrolling for <settings-dialog>

chrome/browser/resources/settings/settings_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 'settings-dialog' is a component for showing a modal dialog.
  */
 Polymer({
   is: 'settings-dialog',
 
   properties: {
     /** @override */
     noCancelOnOutsideClick: {
       type: Boolean,
       value: true,
     },
 
     /** @override */
     noCancelOnEscKey: {
       type: Boolean,
       value: false,
     },
 
+    sizingTarget: {
+      type: Element,
+      value: function() {
+        return this.$$('.body-container');
+      },
+    },
+
     /** @override */
     withBackdrop: {
       type: Boolean,
       value: true,
     },
   },
 
   behaviors: [Polymer.PaperDialogBehavior],
 
   /** @return {!PaperIconButtonElement} */
   getCloseButton: function() {
     return this.$.close;
   },
 });