Revert of [LayoutNG] Re-enable virtual/layout_ng/

Revert of [LayoutNG] Re-enable virtual/layout_ng/ (patchset #2 id:20001 of https://codereview.chromium.org/2822683002/ )

Reason for revert:
This change causes tests to run on multiple shards.

Original issue's description:
> [LayoutNG] Re-enable virtual/layout_ng/
> 
> This was re-enabled in r464517[1] but wasn't really enabled due to
> incorrect directory name.
> 
> This patch also fixes test runner to find reference files from
> MANIFEST.json for virtual test suites.
> 
> [1] https://chromium-review.googlesource.com/c/474177/
> 
> BUG=636993, 706118
> 
> Review-Url: https://codereview.chromium.org/2822683002
> Cr-Commit-Position: refs/heads/master@{#464705}
> Committed: https://chromium.googlesource.com/chromium/src/+/fc7300a1028fff4c528fa32f1529a3e8cbb1998f

TBR=qyearsley@chromium.org,tkent@chromium.org,kojii@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=636993, 706118

[mithro, 2017-04-20 05:40:55]

Created Revert of [LayoutNG] Re-enable virtual/layout_ng/

[kojii, 2017-04-20 06:58:35]

Thank you tansell.

Could you mind to explain a bit more what the problem is, so that we can
investigate?
> This change causes tests to run on multiple shards.

[mithro, 2017-04-20 07:53:38]

On 2017/04/20 06:58:35, kojii wrote:
> Thank you tansell.
> 
> Could you mind to explain a bit more what the problem is, so that we can
> investigate?
> > This change causes tests to run on multiple shards.

I ended up finding a small way to do the revert, see
https://codereview.chromium.org/2831053002

[kojii, 2017-04-20 23:49:14]

Oh, ok, so this didn't land. Thank you and sorry for the trouble in the other
CL.