autoroll: Remove use of http.Get().
autoroll: Remove use of http.Get().

BUG=skia:
R=rmistry

Review-Url: https://codereview.chromium.org/2128603002

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