grafana: Upgrade to 3.1.0
grafana: Upgrade to 3.1.0

BUG=skia:
TBR=borenet

Review-Url: https://codereview.chromium.org/2159773002

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