This is a reland of 3b065110
Original change's description:
> Reland "[test] Creating command before execution phase."
> 
> This is a reland of 98cc9e86
> Original change's description:
> > [test] Creating command before execution phase.
> > 
> > Immutable command class with shell, flags and
> > environment.
> > 
> > Command creation moved from worker to the main
> > process. Because of that there is no need to send
> > test cases beyond process boundaries and load test
> > suites in worker processes.
> > 
> > Bug: v8:6917
> > Change-Id: Ib6a44278095b4f7141eb9b96802fe3e8117678a6
> > Reviewed-on: https://chromium-review.googlesource.com/791710
> > Commit-Queue: Michał Majewski <majeski@google.com>
> > Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#49746}
> 
> Bug: v8:6917
> Change-Id: I49c29a8db813c47909f2cc45070ac7721a447c7a
> Reviewed-on: https://chromium-review.googlesource.com/800370
> Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> Commit-Queue: Michał Majewski <majeski@google.com>
> Cr-Commit-Position: refs/heads/master@{#49756}

Bug: v8:6917
Change-Id: Ia39010a0a0f63537ad12490dfab17897d70d4930
Reviewed-on: https://chromium-review.googlesource.com/806034Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michał Majewski <majeski@google.com>
Cr-Commit-Position: refs/heads/master@{#49830}