Warnings about implicit type conversions were showing up as errors on
MSVS 2017.

TEST=build with MSVS 2017

Change-Id: I5f173a6838da16e96fad134756d31f56890c147b
Reviewed-on: https://chromium-review.googlesource.com/778841
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>