Decrease TTRR (time to relay request) by lazy rendering fake group header

Reviewed By: astreet

Differential Revision: D3155945

fb-gh-sync-id: b8ab8934555428aef98901288edc66d9ef251d96
fbshipit-source-id: b8ab8934555428aef98901288edc66d9ef251d96

Libraries/Components/LazyRenderer.js

@@ -0,0 +1,42 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule LazyRenderer
+ */
+'use strict';
+
+var React = require('React');
+var TimerMixin = require('TimerMixin');
+
+var LazyRenderer = React.createClass({
+  mixin: [TimerMixin],
+
+  propTypes: {
+    render: React.PropTypes.func.isRequired,
+  },
+
+  componentWillMount: function(): void {
+    this.setState({
+      _lazyRender : true,
+    });
+  },
+
+  componentDidMount: function(): void {
+    requestAnimationFrame(() => {
+      this.setState({
+        _lazyRender : false,
+      });
+    });
+  },
+
+  render: function(): ?ReactElement {
+    return this.state._lazyRender ? null : this.props.render();
+  },
+});
+
+module.exports = LazyRenderer;