Better handling of processing 3d tiles

[lilleyse]

While running a Draco compressed tileset we noticed that tiles seems to be streaming in reverse order. The problem was we were iterating over the processing queue in reverse order, mainly as a convenience since elements could be removed during iteration. In this tileset downloading tiles is much quicker than processing so the processing queue was stuffed with tiles and kept on processing the low priority tiles first.

The fix was to iterate in forward order and afterwards filter out tiles that are done processing.

Before/after:

[cesium-concierge]

@lilleyse, thanks for the pull request! Maintainers, we have a signed CLA from @lilleyse, so you can review this at any time.

⚠️ I noticed that CHANGES.md has not been updated. If this change updates the public API in any way, fixes a bug, or makes any non-trivial update, please add a bullet point to CHANGES.md and comment on this pull request so we know it was updated. For more info, see the Pull Request Guidelines.

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[lilleyse]

I'm not sure why 3 of the tests fail in travis but not locally... I'll keep looking.

[pjcozzi]

Update CHANGES.md and add a unit test if possible. Are you also porting this to your refactor?

[lilleyse]

Fixed the tests. One of the files in the i3dm specs data folder was called Box.glb instead of box.glb. The output from 3d-tiles-tools/sampler-generator looks fine so I'm not sure how that happened. The code here must have exposed that problem in some way.

I also updated CHANGES.md but didn't write a new test because it was too dependent on load order and the test started to get complicated.

Are you also porting this to your refactor

Yeah these changes will fit in fine there.

[lilleyse]

Do we want this in before 1.44? It will help loading if there are any Draco tilesets out there.

Otherwise if it doesn't matter much I can target the request-performance branch instead.

[pjcozzi]

If we are going to message Draco support, we should merge this.

[hpinkos]

If this is making it in the release it needs to be merged tomorrow. @lilleyse who do you think should review this?

[lilleyse]

@likangning93 given that you are slated to review some of the other 3D Tiles PRs maybe it makes sense to review this too?

[lilleyse]

For whoever is reviewing, this code is based on a similar filter function in RequestScheduler

[lilleyse]

Ah I forgot @likangning93 is out today - @bagnell could you review today?