I am aware of this alternative, but that's not currently supported by
js. Basically you return a writable buffer to js by MapBufferRange.
Now you need to keep track of which part are dirty and which are
clean. I am not saying it's impossible, but requires new semantics
I don't see this can be better than BufferSubData in out-of-process
There are many other examples that we have to hold back features that
developers would love, for example, certain compressed texture formats
not supported on iOS, etc. It may seem frustrating but in the long
run, good for WebGL as a web standard.