Fix non-otr profile's file manager being launched in guest mode.

There are two issues:
1. App laucher uses the active profile's original profile to determine
if we're in guest mode (and thus always assuming guest session is not
active).
2. Every file manager event router (each profile has one) opening
a file manager window when removable device is inserted. So the
original profile's event router will open a window too.

BUG=329658
TEST=
1. Login as guest, launch file manager from the app launcher, open a doc file
from the file manager using quick office, and verify the doc is opened in off
the record window (Ctrl-T should open guest tab).
2. Login as guest, insert an SD card, make sure only 1 file manager window is
opened. From the opened file manager window, open a doc file using quick
office and make sure the document is opened in off the record window.

Review URL: https://codereview.chromium.org/115733007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243474 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243474