Revert of Convert startup_metric_utils to use mojo. (patchset #6 id:240001 of https://codereview.chromium.org/2022413002/ )

Reason for revert:
Breaks mac compilation.

Original issue's description:
> Convert startup_metric_utils to use mojo.
>
> BUG=577685
> TBR=jochen@chromium.org
>
> Committed: https://crrev.com/089f995b33d52e072a1a00c0302116fb9d4e49fb
> Cr-Commit-Position: refs/heads/master@{#398781}

TBR=dcheng@chromium.org,erikchen@chromium.org,sky@chromium.org,jochen@chromium.org,sammc@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=577685

Review-Url: https://codereview.chromium.org/2048033004
Cr-Commit-Position: refs/heads/master@{#398816}
28 files changed