We might not be able to prepare a material on the first frame we
encounter a mesh using it for various reasons, including that the
material hasn't been loaded yet or that preparing the material is
exceeding the per-frame cap on number of bytes to load. When this
happens, we currently try to find the material in the
`MaterialBindGroupAllocator`, fail, and then fall back to group 0, slot
0, the default `MaterialBindGroupId`, which is obviously incorrect.
Worse, we then fail to dirty the mesh and reextract it when we *do*
finish preparing the material, so the mesh will continue to be rendered
with an incorrect material.
This patch fixes both problems. In `collect_meshes_for_gpu_building`, if
we fail to find a mesh's material in the `MeshBindGroupAllocator`, then
we detect that case, bail out, and add it to a list,
`MeshesToReextractNextFrame`. On subsequent frames, we process all the
meshes in `MeshesToReextractNextFrame` as though they were changed. This
ensures both that we don't render a mesh if its material hasn't been
loaded and that we start rendering the mesh once its material does load.
This was first noticed in the intermittent Pixel Eagle failures in the
`testbed_3d` patch in #17898, although the problem has actually existed
for some time. I believe it just so happened that the changes to the
allocator in that PR caused the problem to appear more commonly than it
did before.
465306bc5e