Group functions writing test files together

This is to simplify the diff in the follow up CL. The code was moved
untouched.

Bug: 330885075
Change-Id: Ic47809d315a994aa7b6c452c6e11d72d394f0076
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5392102


Commit-Queue: Jean-Philippe Gravel <jpgravel@chromium.org>
Reviewed-by: Andres Ricardo Perez <andresrperez@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1282150}