A std::min/max with size_t and unsigned int.

Popped up in f98e63a5.

BUG=

Change-Id: I25f26ddbe7fb333f895be8a8dce3d3d73044c3f9
Reviewed-on: https://chromium-review.googlesource.com/200484Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>