sheriff-o-matic's partytime should update based off the failures' length.

As it is now, it's bound to the failure object's identity. When we change that
to not change on each update, we'll show partytime incorrectly.

R=jyasskin@chromium.org

Review URL: https://codereview.chromium.org/506493002

git-svn-id: svn://svn.chromium.org/blink/trunk@181117 bbb929c8-8fbe-4397-9dbb-9b2b20218538