[Ygg2]

>I think it is fair to say that if someone started with today's web/mobile requirements and designed a language from scratch to meet performance, latency, and memory requirements as well as portability/cross platform execution

True, but so is that developing a simpler, cruder and slower but Fast Enough alternative to said language, would take less time and by the time the said alternative would developer, they would be on same feature parity.

> That is, you're comparing 15+ years of Javascript JIT engineering activity with what, 2-3 years of PNaCL activity by a much smaller team?

No, I'm comparing asm.js engineering (if you can call it that), to (P)NaCl.

JS performance improvements was a weird road to take, but JS of old days wasn't the JS of new days. It's use case was significantly different and Google wanted to enable new use cases for it to run it's Gmail program. So they did.