This will compile with and without the flag, and compare the compiled output files (ignoring the json files).
If you patch this in you can run this locally by doing:
BUILDBOT_BUILDERNAME=dart2js-dump-info client/tools/buildbot_annotated_steps.py
or
BUILDBOT_BUILDERNAME=dart2js-dump-info python tools/bots/dart2js_dump_info.py
R=whesse@google.com
Review URL: https://codereview.chromium.org//506863002
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@39546 260f80e4-7a28-3924-810f-c04153c831b5