spanification: Add `#pragma allow_unsafe_buffers` follow-up chromeos.

This is a preparation to fix each files. This CL has no behavior.
changes. This patch was fully automated using script:
https://paste.googleplex.com/5614491201175552

I realized I missed building for chromeos and chromeos-ash, so this
requires a follow-up to: //chrome, //components, //media, //services, //ui
- https://chromium-review.googlesource.com/c/chromium/src/+/5717950
- https://chromium-review.googlesource.com/c/chromium/src/+/5717952
- https://chromium-review.googlesource.com/c/chromium/src/+/5717833
- https://chromium-review.googlesource.com/c/chromium/src/+/5717832

See internal doc about it:
https://docs.google.com/document/d/1erdcokeh6rfBqs_h0drHqSLtbDbB61j7j3O2Pz8NH78/edit?resourcekey=0-hNe6w1hYAYyVXGEpWI7HVA&tab=t.0

Bug: 40285824
AX-Relnotes: n/a
Change-Id: I7e40deb45147e82e12e1a7834e2acc036230b29d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5757691
Owners-Override: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Auto-Submit: Arthur Sonzogni <arthursonzogni@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1336709}