Current behavior:
When trying to use the texture format rgba8uint as destination for a copyExternalImageToTexture from a PNG, Chrome reports an invalid destination format.

Expected behavior:
Copying to a uint texture does a byte-exact copy from the source pixel data.

The spec does not mention pixel formats specifically for external texture copies... the implication seems to be that color space conversion would require a float / unorm source and destination.

It is useful to use uints if you e.g. have data losslessly encoded in a .PNG and wish to sample it directly on the GPU. Right now you have to decode it with ImageDecoder and then upload it as a buffer instead.