[gerrit] Support the revisions field on a change
[gerrit] Support the revisions field on a change

This change adds support for 'revisions' in a Change which gives
information about patch sets.

R=ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org,tandrii@chromium.org

Change-Id: I4bc739f3b12d20eb76db57f7ad63c9d6e04ac586
Reviewed-on: https://chromium-review.googlesource.com/1232533
Commit-Queue: Michael Knyszek <4473450dc5c88f06e1fb787f303d7805ec2aee65@google.com>
Reviewed-by: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go