perf server: populate annotations into Commit.
perf server: populate annotations into Commit.

BUG=skia:
NOTRY=true
R=jcgregorio@google.com, kelvinly@google.com

Author: bensong@google.com

Review URL: https://codereview.chromium.org/331373007

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