Fixed compiler warning C4267 'conversion from 'size_t' to 'type', possible loss of data' BUG=angleproject:1120 Change-Id: I01ef10bea7f487c2b394d030c76628f38d2ea645 Reviewed-on: https://chromium-review.googlesource.com/292780 Tested-by: Cooper Partin <coopp@microsoft.com> Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>