factory: Refine X startup procedure to allow better board customization.

Note board config file is explicitly renamed to prevent incompatibility.

Now each board may define and override arbitrary steps (and variables) in X
startup.

BUG=chrome-os-partner:8179
TEST=start factory # X starts correctly

Change-Id: Ifd1b123466eff21cd5d5c71a870a21640f7b7ba9
Reviewed-on: https://gerrit.chromium.org/gerrit/18351
Reviewed-by: Jon Salz <jsalz@chromium.org>
Commit-Ready: Hung-Te Lin <hungte@chromium.org>
Tested-by: Hung-Te Lin <hungte@chromium.org>
2 files changed