MD WebUI: Simplify usage of Templatizer in cr-lazy-render

chrome/browser/resources/md_history/app.crisper.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.
 function PromiseResolver() {
   this.resolve_;
   this.reject_;
   this.promise_ = new Promise(function(resolve, reject) {
     this.resolve_ = resolve;
     this.reject_ = reject;
   }.bind(this));
@@ skipping 5370 matching lines @@
 });
 
 // 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.
 Polymer({
   is: 'cr-lazy-render',
   "extends": 'template',
   behaviors: [ Polymer.Templatizer ],
   _renderPromise: null,
-  _instance: null,
+  _child: null,
   get: function() {
     if (!this._renderPromise) {
       this._renderPromise = new Promise(function(resolve) {
         this._debounceTemplate(function() {
           this._render();
           this._renderPromise = null;
           resolve(this.getIfExists());
         }.bind(this));
       }.bind(this));
     }
     return this._renderPromise;
   },
   getIfExists: function() {
-    if (this._instance) {
-      var children = this._instance._children;
-      for (var i = 0; i < children.length; i++) {
-        if (children[i].nodeType == Node.ELEMENT_NODE) return children[i];
-      }
-    }
-    return null;
+    return this._child;
   },
   _render: function() {
     if (!this.ctor) this.templatize(this);
     var parentNode = this.parentNode;
-    if (parentNode && !this._instance) {
-      this._instance = this.stamp({});
-      var root = this._instance.root;
-      parentNode.insertBefore(root, this);
+    if (parentNode && !this._child) {
+      var instance = this.stamp({});
+      this._child = instance.root.querySelector('*');
+      parentNode.insertBefore(instance.root, this);
     }
   },
   _forwardParentProp: function(prop, value) {
-    if (this._instance) this._instance.__setProperty(prop, value, true);
+    if (this._child) this._child._templateInstance[prop] = value;
   },
   _forwardParentPath: function(path, value) {
-    if (this._instance) this._instance._notifyPath(path, value, true);
+    if (this._child) this._child._templateInstance.notifyPath(path, value, true);
   }
 });
 
 (function() {
   'use strict';
   Polymer.IronA11yAnnouncer = Polymer({
     is: 'iron-a11y-announcer',
     properties: {
       mode: {
         type: String,
@@ skipping 3260 matching lines @@
 
        case HistoryRange.MONTH:
         histogramValue = HistoryPageViewHistogram.GROUPED_MONTH;
         break;
       }
       break;
     }
     md_history.BrowserService.getInstance().recordHistogram('History.HistoryPageView', histogramValue, HistoryPageViewHistogram.END);
   }
 });