Further tweak compare_codereview.py.

- only show details for bots where at least one side failed
- dedup identical failures

BUG=skia:
R=halcanary@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/202113008

git-svn-id: http://skia.googlecode.com/svn/trunk@13942 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed