Fix module IDs of initial require calls

Summary: The logic of assigning module IDs to the initial require calls of a bundle was faulty, counting up from -1 instead of counting down. This change ensures that IDs are -1, -2, ...

Reviewed By: matryoshcow

Differential Revision: D3735560

fbshipit-source-id: 89efa3e73b39c2f8bfed8a6a30487733d1a8b145

Author: davidaurelio

packager/react-packager/src/Bundler/Bundle.js

@@ -67,7 +67,7 @@ class Bundle extends BundleBase {
     const name = 'require-' + moduleId;
     super.addModule(new ModuleTransport({
       name,
-      id: this._numRequireCalls - 1,
+      id: -this._numRequireCalls - 1,
       code,
       virtual: true,
       sourceCode: code,