hook up offscreen api to runApplication

Summary:
[Changelog]: Internal

integrate the offscreen component when we render an application that is configured to do so

Reviewed By: rubennorte

Differential Revision: D39458472

fbshipit-source-id: 9bd492ca258723cb9cf0b7e4f6c9b0005554e91e

Author: philIip

Libraries/ReactNative/renderApplication.js

@@ -9,11 +9,11 @@
  */
 
 import type {IPerformanceLogger} from '../Utilities/createPerformanceLogger';
-import type {DisplayModeType} from './DisplayMode';
 
 import GlobalPerformanceLogger from '../Utilities/GlobalPerformanceLogger';
 import PerformanceLoggerContext from '../Utilities/PerformanceLoggerContext';
 import AppContainer from './AppContainer';
+import DisplayMode, {type DisplayModeType} from './DisplayMode';
 import getCachedComponentWithDebugName from './getCachedComponentWithDebugName';
 import * as Renderer from './RendererProxy';
 import invariant from 'invariant';
@@ -22,6 +22,11 @@ import * as React from 'react';
 // require BackHandler so it sets the default handler that exits the app if no listeners respond
 import '../Utilities/BackHandler';
 
+type OffscreenType = React.AbstractComponent<{
+  mode: 'visible' | 'hidden',
+  children: React.Node,
+}>;
+
 export default function renderApplication<Props: Object>(
   RootComponent: React.ComponentType<Props>,
   initialProps: Props,
@@ -34,6 +39,7 @@ export default function renderApplication<Props: Object>(
   debugName?: string,
   displayMode?: ?DisplayModeType,
   useConcurrentRoot?: boolean,
+  useOffscreen?: boolean,
 ) {
   invariant(rootTag, 'Expect to have a valid rootTag, instead got ', rootTag);
 
@@ -64,6 +70,19 @@ export default function renderApplication<Props: Object>(
     );
   }
 
+  if (useOffscreen && displayMode != null) {
+    // $FlowFixMe[incompatible-type]
+    // $FlowFixMe[prop-missing]
+    const Offscreen: OffscreenType = React.unstable_Offscreen;
+
+    renderable = (
+      <Offscreen
+        mode={displayMode === DisplayMode.VISIBLE ? 'visible' : 'hidden'}>
+        {renderable}
+      </Offscreen>
+    );
+  }
+
   performanceLogger.startTimespan('renderApplication_React_render');
   performanceLogger.setExtra(
     'usedReactConcurrentRoot',