GPUTextureDescriptor constructor
usage is a bitwise or of GpuTextureUsage values.
A cube map is dimension "2d" with a size whose depthOrArrayLayers is
six — the cube-ness is a property of the view, not of the texture, which
is the one place this API is simpler than the ones the other three
backends sit on.
Implementation
external factory GPUTextureDescriptor({
GPUExtent3DDict size,
String format,
int usage,
int sampleCount,
int mipLevelCount,
String dimension,
String label,
});