Export init function

Summary: This way we can mock it during tests.

Reviewed By: jknoxville

Differential Revision: D9788349

fbshipit-source-id: 55b2a61186e6294a8098db7add50fd8bbac7a680

src/init.js

@@ -62,16 +62,18 @@ const AppFrame = () => (
   </TooltipProvider>
 );
 
-// $FlowFixMe: this element exists!
-ReactDOM.render(<AppFrame />, document.getElementById('root'));
-// $FlowFixMe: service workers exist!
-navigator.serviceWorker
-  .register(
-    process.env.NODE_ENV === 'production'
-      ? path.join(__dirname, 'serviceWorker.js')
-      : './serviceWorker.js',
-  )
-  .then(r => {
-    (r.installing || r.active).postMessage({precachedIcons});
-  })
-  .catch(console.error);
+export default function init() {
+  // $FlowFixMe: this element exists!
+  ReactDOM.render(<AppFrame />, document.getElementById('root'));
+  // $FlowFixMe: service workers exist!
+  navigator.serviceWorker
+    .register(
+      process.env.NODE_ENV === 'production'
+        ? path.join(__dirname, 'serviceWorker.js')
+        : './serviceWorker.js',
+    )
+    .then(r => {
+      (r.installing || r.active).postMessage({precachedIcons});
+    })
+    .catch(console.error);
+}