Fix import error "AttributeError: 'module' object has no attribute 'factory'"

As found by Hung-Te, in https://chromium-review.googlesource.com/329833,
Fix import error by using from.

BUG=none
TEST=Build images.

Change-Id: I22f311a15dac235f178a2b33da4ac07172969a15
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/338927
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
12 files changed