GitLab

This CL begins organizing code for Feed v2 by pulling some enums
into a new common directory.

Putting shared code in a different place makes it easier to understand
implications of modifying code, and will make it easier to understand
what pieces of code effect the 'v2' effort.

I'm starting with a few enums because they are very likely to remain
identical. More code will be moved here soon.

Bug: 1044139
Change-Id: I51f83f2fdc212aba9f72a1e9afd2ef8e79437e0a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2012903
Commit-Queue: Dan H <harringtond@chromium.org>
Reviewed-by: Carlos Knippschild <carlosk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734195}