Convert MessageWriter APIs to base::span

Change-Id: Ib24b299232e6f0c09556d4e9d6ccbf07c5efce96
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5126612
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Owners-Override: danakj <danakj@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1239219}
NOKEYCHECK=True
GitOrigin-RevId: 71bf932284c234fbbfe9c8ff987fc0f9dff7658e
6 files changed