pre-upload: use RawDiff from chromite

BUG=chromium:397714
TEST=upload checks still work

Change-Id: I7695adb51fbb4a7da72c5f7cba1646950c36753b
Reviewed-on: https://chromium-review.googlesource.com/231613
Reviewed-by: Doug Anderson <dianders@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
2 files changed