bench_pictures: whitelist only bots which have bench expectations.
bench_pictures: whitelist only bots which have bench expectations.

BUG=skia:
R=borenet@google.com, bsalomon@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/482743002

google/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot