GitLab

While here, also slightly reorganize chromium.memory console layout:
- Consistently use OS as toplevel subcategory (so that we don't have
  the cros msan bots under "linux|cros" while the cros asan bots are under
  "asan|cros"
- Order OSs in the same order as the per-os waterfalls appear on
  build.chromium.org: win, mac, linux, cros.

In mb_config.pyl, remove obsolete 'x86' from win/asan config names,
and stop explicitly passing 'x64' (it's the default).

This adds the bot config, but it doesn't add any tests yet. I'll do this
in a follow-up so that I can send try jobs before adding tests. Before
tests are landed, the bot will do nothing.

Bug: 869973
Change-Id: I68a1a401b3fef1532006e42ab7f0e80d1532aa94
Reviewed-on: https://chromium-review.googlesource.com/1163932
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Ryan Tseng <hinoka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581094}