RAM Bundles: Incorrect line mappings

The line mappings resolved from metro-symbolicate for RAM bundled applications appear to be broken.

I've created a simple example repository which uses the latest release of React Native (v0.59.5) and includes four crash scenarios (each one can be triggered by pressing the corresponding button).

Before enabling RAM bundles, I grabbed the line and column numbers from the top frame from each resulting stacktrace and converted them using the symbolicate.js script in metro-symbolicate and got the expected mappings, i.e.

• Unhandled error 1 : App.js:13
• Unhandled error 2 : App.js:21
• Unhandled error 3 : badCode.js:3
• Handled error 1 : App.js:32

I repeated the same test after enabling RAM bundles but passing the associated filenames for each frame into symbolicate.js, e.g.

./symbolicate.js <path-to-source-map> 364.js 1 250 

And the resulting mappings are out of alignment (for both iOS and Android):

• Unhandled error 1 : App.js:10
• Unhandled error 2 : App.js:20
• Unhandled error 3 : badCode.js:1
• Handled error 1 : App.js:45 <-- In this case the mapping is quite far away from the crashing line

I've included the command I used to generate the associated source maps in the readme of the example repository.

Start with packages/metro-symbolicate/src/symbolicate.js and the linked RamBundleInvestigation README, then run its four crash scenarios for both iOS and Android. Compare the generated source maps and symbolicated results with the expected App.js and badCode.js locations; done means the RAM bundle mappings align with the crashing lines.