This reverts commit 712fa675.

Reason for revert: Infra side change was reverted. Please reland
after it stays in for a bot cycle...

Original change's description:
> [test] Add Liftoff variant
> 
> Add a variant for testing the current state of the Liftoff
> implementation.
> This variant will only run on a subset of the bots, just like the
> --future variant.
> 
> R=​machenbach@chromium.org, hablich@chromium.org
> 
> Bug: v8:7088, v8:6600
> Change-Id: If49fad3a8ed579356504b821a787326754f24e78
> Reviewed-on: https://chromium-review.googlesource.com/779420
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#49504}

TBR=machenbach@chromium.org,hablich@chromium.org,clemensh@chromium.org

Change-Id: Ib6b2e79cea5d9f99f8933c72bbb9d9dddbd6ae07
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7088, v8:6600
Reviewed-on: https://chromium-review.googlesource.com/779719Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49507}