Data indicate that Android renderers are crashing in sandbox::CrashSIGSYS_Handler, but we do not know the sysno. Per https://cs.chromium.org/chromium/src/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc?q=CrashSIGSYS_Handler&sq=package:chromium&dr=CSs&l=127 we try and record the nr as part of the exception address. But for this set of crashes, masking 0x3ff of the violation results in 0. Looking at the stack memory dumps from these crashes, it's also not easy to see what the faulting system call number is. (It appears the value gets aliased).

In order to track down these crashes, we should record a crash key with the seccomp information.