login_manager: Clear the framebuffer after X starts.
login_manager: Clear the framebuffer after X starts.

Part of an ongoing effort to make shutdown less janky.

Change-Id: I56e2a5c2a9bd0f69988a8114c427bf3be4329d58

BUG=chromium-os:4279
TEST=tried it

Review URL: http://codereview.chromium.org/3278007

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