Earlier quoted context omitted.
First you compromise the renderer process via e.g. a bug in the JS engine. But even if you have native code execution in the context of the renderer process, you're still in a sandbox. The bug in the OP is for the second stage - breaking out of the sandbox. The referenced `patch.diff` is basically for simulating a compromised renderer.
Ah, so it's like a two stage rocket, this turns a small exploit into a humongous one?
Once you're thinking along the lines of "Alright, if I had some order of flags, I could solve that thing over there. If I knew some kind of weights, I could solve that over there. And if I could find a light bulb I could deal with that over there", you're kinda in the mindset of finding an exploitation chain.
It's just that in the security world, it's more about bad memory accesses, confusing programs into doing the right actions with wrong files, file permissions being weird and such.