Add a warning comment to the critical path following X startup completion.
Add a warning comment to the critical path following X startup completion.

BUG=chromium-os:13449
TEST=boot the system

Review URL: http://codereview.chromium.org/6732011

Change-Id: I3097bcf47c62919486461621da581b7d74d1ba0d

chadversary/chromiumos.platform.login_manager,joshfire/chromiumos-platform-login_manager,joshfire/chromiumos-platform-login_manager,chadversary/chromiumos.platform.login_manager,joshfire/chromiumos-platform-login_manager,chadversary/chromiumos.platform.login_manager