Change Draco modules to be created asynchronously

[FrankGalligan]

In general Draco npm modules have always been created asynchronously. But in gltf-pipeline they worked usually with getting created synchronously.

We are planning to release Draco 1.4.0, which uses a new version of emscripten and causes gltf-pipline to fail as the timing has changed.

The change in this PR makes it so the current version of the Draco npm modules work and it will work when 1.4.0 is released.

The question is is there a better way to create the Draco modules asynchronously in gltf-pipeline?

[FrankGalligan]

@lilleyse Any issue with this PR? We want to release a new version of Draco as soon as we can and we really don't want to break gltf-pipeline.

[lilleyse]

@FrankGalligan I tried out another approach that's more self-contained in compressDracoMeshes but I'm constantly getting Maximum call stack size exceeded not matter what I try. Could you take a look if I'm doing anything wrong? https://github.com/CesiumGS/gltf-pipeline/compare/draco-async?expand=1

[FrankGalligan]

@lilleyse Your branch worked for me using Draco 1.3.6 (the current version). Also I think I created a PR by mistake #562

[FrankGalligan]

@lilleyse I can reproduce the error you are seeing with Draco 1.3.6.

I had the newer modules when I was testing before. So your code works with the next release of Draco npm modules but doesn't work with Draco npm 1.3.6

I will see if I can debug what is going on with 1.3.6

[FrankGalligan]

@lilleyse Unfortunately I really only program in JavaScript to make changes to gltf-pipeline, so my experience is very minimal.

I can see it gets into this function and returns:
https://github.com/CesiumGS/gltf-pipeline/blob/draco-async/lib/compressDracoMeshes.js#L58

Then it tries to run compress stage and then it breaks. From the error message it looks like you might have an infinite recursion.

Can the promise just keep creating another promise?

[lilleyse]

The infinite recursion seems to be some strange interaction between the promise and the Draco module internals, and I can't seem to figure out why.

But if it's working in 1.4.0 then I can publish a gltf-pipeline release locked to 1.3.6 and then publish a new release once 1.4.0 is out. If that sounds good I'll go ahead with the first release.

[lilleyse]

@FrankGalligan now that #563 is merged you can go ahead and release Draco 1.4.0

[lilleyse]

Fixed in #562