Removing old M-31 flag which suppressed the multi user menu in the system shelf (and which is always set)

Code removed!

BUG=307046
TEST=visual, unit test changed and still works

Review URL: https://codereview.chromium.org/27260002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228588 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228588