[Sheriff-o-matic] Remove race condition on the commit list.

By always modifying the same list of commits, we ensure that data binding does The Right Thing and updates when data comes in.

As well, renamed "revisionLog" to "commitLog" everywhere, to better reflect the data type.

BUG=405327
NOTRY=true

Review URL: https://codereview.chromium.org/485253004

git-svn-id: svn://svn.chromium.org/blink/trunk@180728 bbb929c8-8fbe-4397-9dbb-9b2b20218538