MD Settings: Lazy load the contents of the "advanced" settings.

chrome/browser/resources/settings/controls/settings_idle_render.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
- * settings-idle-render is a simple variant of dom-if designed for lazy
- * rendering of elements that are accessed imperatively.
- * If a use for idle time expansion is found outside of settings, this code
- * should be replaced by cr-lazy-render after that feature is merged into
- * ui/webui/resources/cr_elements/cr_lazy_render/cr_lazy_render.js
- */
-
-Polymer({
-  is: 'settings-idle-render',
-  extends: 'template',
-
-  behaviors: [Polymer.Templatizer],
-
-  /** @private {TemplatizerNode} */
-  child_: null,
-
-  /** @private {number} */
-  idleCallback_: 0,
-
-  /** @override */
-  attached: function() {
-    this.idleCallback_ = requestIdleCallback(this.render_.bind(this));
-  },
-
-  /** @override */
-  detached: function() {
-    // No-op if callback already fired.
-    cancelIdleCallback(this.idleCallback_);
-  },
-
-  /**
-   * Stamp the template into the DOM tree synchronously
-   * @return {Element} Child element which has been stamped into the DOM tree.
-   */
-  get: function() {
-    if (!this.child_)
-      this.render_();
-    return this.child_;
-  },
-
-  /** @private */
-  render_: function() {
-    if (!this.ctor)
-      this.templatize(this);
-    var parentNode = this.parentNode;
-    if (parentNode && !this.child_) {
-      var instance = this.stamp({});
-      this.child_ = instance.root.firstElementChild;
-      parentNode.insertBefore(instance.root, this);
-    }
-  },
-
-  /**
-   * @param {string} prop
-   * @param {Object} value
-   */
-  _forwardParentProp: function(prop, value) {
-    if (this.child_)
-      this.child_._templateInstance[prop] = value;
-  },
-
-  /**
-   * @param {string} path
-   * @param {Object} value
-   */
-  _forwardParentPath: function(path, value) {
-    if (this.child_)
-      this.child_._templateInstance.notifyPath(path, value, true);
-  }
-});