Run Chrome in background from xsession file.
Run Chrome in background from xsession file.

This gets it up and running a bit faster than when we launch
it from within the window manager (at least, that is my
perception).  I also changed the WM to create the compositing
overlay window early on, to reduce the chances that Chrome's
window will get mapped first (which would create a weird
effect where Chrome appears but then disappears and slides
back onscreen from the right).

Review URL: http://chromereview.prom.corp.google.com/1176060

git-svn-id: 59a3318ba88c04536d83f47c63c52b7f675c4a1a@71 06c00378-0e64-4dae-be16-12b19f9950a1

joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager