Sampler.cpp: Fix a warning on Linux and Mac BUG= Change-Id: I58a19de9d5978aa4d65ac2ab1acd2fbd233ec6a2 Reviewed-on: https://chromium-review.googlesource.com/302463 Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>