Fix MSVC 2015 warnings. BUG=angleproject:2258 Change-Id: I280eb0e461fd749b01594bb1bb9a417f2cbc23fa Reviewed-on: https://chromium-review.googlesource.com/793975 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>