I hope you are kidding.
JIT's often have a large number of crashing bugs, usually even more than static compilers (because it is often hard to reproduce every set of circumstances that cause something to happen, unlike static compilers)
The point is that the probability that JS code will segfault the browser is dramatically less than the probability that C++ code will segfault the browser.
I don't believe this for a second.
I might believe it if you said "the probability that commonly used JS code will segfault the browser is dramatically less than the probability that browser-specific C++ code will segfault the browser". Which would be a very different claim.
Remember that most JS is popular JS, with some small amount of custom lines. JS seems less crashy because people don't use as much "random" JS in general.
