MEMFS.stream_ops.write broken on legacy browsers

[JustAMan]

Hi!

I'm using emscripten to compile a C library to render subtitles on the fly, and during debugging why it won't work on older WebOS models I found that recent PR has introduced an incompatibility with legacy browsers. I'm speaking of #10347 - in older browsers I found that Uint8Array doesn't have .slice() member (at least in worker context, in some not-so-ancient it has .slice() in normal context but not within web worker).

[kripken]

Thanks @JustAMan !

I opened #11011 now to add automatic polyfilling there, can you please test it?

[stale]

This issue has been automatically marked as stale because there has been no activity in the past year. It will be closed automatically if no further activity occurs in the next 30 days. Feel free to re-open at any time if this issue is still relevant.