CHROMIUM: automatically mount tmpfs at /tmp at boot

We have a small pre-startup shell script that mounts /tmp.  This
is relatively expensive for what is 1 syscall.  Since we consider
/tmp to be absolutely required as part of the system, and we always
want it to be tmpfs, move the setup to upstart itself to simplify.

BUG=chromium:1063545
TEST=CQ passes

Change-Id: Ib13881e08fb847ce510f69b4fb44b45daf780ab7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/upstart/+/2546467
Reviewed-by: Allen Webb <allenwebb@google.com>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
3 files changed