it would always run with the Default profile. This meant that two
different users could see the same data...a big problem.
We patched in the OS by deleting the profile directory each time
but this is the right fix.
When the session_manager reruns Chrome on a crash it will now
pass a new flag (--login-user). Chrome uses this and ensures that
the profile dir (specified by --login-profile) is mounted as an
encrypted drive. If this flag isn't specified then Chrome uses the
Default profile, but in incognito mode so no data is written.

BUG=chromiumos:1967
TEST=Login to chromeos as user1, in a terminal kill the browser process, chrome relaunches, log into gmail, sign out (using menu or power button). Login as user2, kill browser process, chrome relaunches, go to gmail. Ensure that user1 isn't logged in.

Review URL: http://codereview.chromium.org/1094009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@42279 0039d316-1c4b-4281-b951-d872f2087c98