This replaces chromium_roll and the wrapper auto_roll with
just auto_roll. The arguments for the revision to roll and
the last rolled revision are optional and will be
auto-detected (this feature is from the wrapper).

Checking the cq box is default now (as in the wrapper).

BUG=chromium:559141
LOG=n
NOTRY=true

Review URL: https://codereview.chromium.org/1468973002

Cr-Commit-Position: refs/heads/master@{#32193}