Restart after changing settings

Summary:
Gets flipper to restart when settings are updated.

In theory most settings should not need this, but the current only one does (android home) because the path is set at startup only, and this modifies the input to it.
It would be a bit awkward to modify the path more than once, but doable.

Reviewed By: passy

Differential Revision: D17737582

fbshipit-source-id: d4669dcc7acc95469f15783fc6a5ba6794750234

src/utils/persistor.tsx

@@ -0,0 +1,20 @@
+/**
+ * Copyright 2018-present Facebook.
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ * @format
+ */
+
+import {Persistor} from 'redux-persist';
+
+let _persistor: Persistor | null = null;
+
+export function setPersistor(persistor: Persistor) {
+  _persistor = persistor;
+}
+
+export function flush(): Promise<void> {
+  return _persistor
+    ? _persistor.flush()
+    : Promise.reject(new Error('Persistor not set.'));
+}