The AsmParser kept pointers into ZoneVectors, which were accessed even
after those vector might have grown. For regular vectors, this would be
a use-after-free; with ZoneVectors it is technically allowed, since the
old memory stays alive. This will change with
https://crrev.com/c/2302895, which zaps zone memory which is
deallocated. Eventually, we might want to reuse large deallocations in
zone memory, hence this "use after free" needs to be fixed.

This CL fixes the issue by explicitly re-allocating in the zone instead
of using ZoneVectors. This makes sure that the old memory stays alive.
This is kind of a quick-fix, but since asm.js is more or less deprecated
anyway (in favor of Wasm), it's OK if this code does not profit from
future ZoneVector memory re-use optimizations.

Drive-by: Move field initializers to the field declaration.

R=ishell@chromium.org

Bug: v8:10717
Change-Id: I56c1feb49d05080e78a6620273b55b4e18156254
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2304581Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68917}