GitLab

This CL adds feature flags and about:flags entries for a couple of
flags:
- MessagesForAndroidInfrastructure will control initialization of
  infrastructure classes (MessageQueueManager, etc.)
- MessagesForAndroidPasswordsName will control whether save/update
  password uses Infobars or Messages UI.

BUG=1123947
R=lazzzis@chromium.org

Change-Id: I4b3e3920d2909f8e6144cc197d8fddc029356f86
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2388949Reviewed-by: Lijin Shen <lazzzis@google.com>
Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Pavel Yatsuk <pavely@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804317}