Overall it looks like this is the main necessary change here. I asked jfb from pnacl how to get code to them, and he pointed them to

http://www.chromium.org/nativeclient/pnacl/developing-pnacl

and

http://dev.chromium.org/developers/contributing-code

which is more general. Looks like you create a chromium.org account, set up the depot stuff, then create the changeset and upload to the review site with one command.

I am ok to merge this before the process ends, but we should get started on this. Until we get it upstream, and merge from upstream, let's mark this change with `// XXX EMSCRIPTEN` like all our local changes.