zero fBuf in new SkXbyakBench

MSAN's keeping me honest...

CQ_INCLUDE_TRYBOTS=skia.primary:Perf-Ubuntu-Clang-GCE-CPU-AVX2-x86_64-Debug-MSAN

Change-Id: If61f75ec919a2b5ae0e973db05760f88588fe18f
Reviewed-on: https://skia-review.googlesource.com/6702
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed