Callers may not need computation of the public key.
Making this optional speeds this routine up.
Cr50 never passes in NULL for any argument, so is not affected.
BUG=none
TEST=build
BRANCH=none
Change-Id: Ia0077a35064f53b53f51867254aaa51eac6c55d8
Reviewed-on: https://chromium-review.googlesource.com/427058
Reviewed-by: Marius Schilder <mschilder@chromium.org>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Tested-by: Marius Schilder <mschilder@chromium.org>