GitLab

Moves the metadata processing for upload into a separate class as it's
somewhat complex but self-contained and has a narrow interface. This also
allows the behavior to be tested more directly, simplifying the tests.

Bug: 976864
Change-Id: Icd608d1665337fa7e8e5168d1e87e529acbd84cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1897359
Commit-Queue: Mike Wittman <wittman@chromium.org>
Reviewed-by: Charlie Andrews <charliea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712789}