Adding show profile switcher field trial.
This sets up a finch server style server controlled field trial to experiment with having the profile switcher always visible.
We want to see the effect this has on sign in.
BUG=172872
TEST=start chrome with --force-fieldtrials=ShowProfileSwitcher/AlwaysShow/ either with a clean user data dir or only one profile. The avatar menu should be visible and there should only be one profile in the profile switcher. You should also be able to edit that profile.
Review URL: https://chromiumcodereview.appspot.com/
12040085
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@180027 0039d316-1c4b-4281-b951-d872f2087c98