RN: Cleanup OSS JS & Flow Declarations

Reviewed By: vjeux

Differential Revision: D4210763

fbshipit-source-id: 5abaa547100b8badd13bcf311ceffc5b4098d252

Libraries/promiseRejectionIsError.js

@@ -9,6 +9,7 @@
  * @providesModule promiseRejectionIsError
  * @flow
  */
+'use strict';
 
 require('Promise'); // make sure the default rejection handler is installed
 const rejectionTracking = require('promise/setimmediate/rejection-tracking');