Created spec for SegmentFetcher native module

Summary: [General] [Added] - Simply adding spec for better enforcement of types.

Reviewed By: cpojer

Differential Revision: D14177690

fbshipit-source-id: ab4c112d1bd65fef7e37b4c1d6c44055f5576936

Libraries/Core/SegmentFetcher/NativeSegmentFetcher.js

@@ -0,0 +1,23 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+'use strict';
+
+import type {TurboModule} from 'RCTExport';
+import * as TurboModuleRegistry from 'TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +fetchSegment: (
+    segmentId: number,
+    options: Object, // flowlint-line unclear-type: off
+    callback: (error: ?Object) => void, // flowlint-line unclear-type: off
+  ) => void;
+}
+
+export default TurboModuleRegistry.getEnforcing<Spec>('SegmentFetcher');

Libraries/Core/setUpSegmentFetcher.js

@@ -18,14 +18,7 @@ global.__fetchSegment = function(
   options: {|+otaBuildNumber: ?string|},
   callback: (?Error) => void,
 ) {
-  const {SegmentFetcher} = require('NativeModules');
-  if (!SegmentFetcher) {
-    throw new Error(
-      'SegmentFetcher is missing. Please ensure that it is ' +
-        'included as a NativeModule.',
-    );
-  }
-
+  const SegmentFetcher = require('NativeSegmentFetcher').default;
   SegmentFetcher.fetchSegment(
     segmentId,
     options,