Revert "chromeos: gets more ash_unittests working with single-process mash"

This reverts commit 41b5497b95c2bc02d527aa4154d4f531e45a0303.

Reason for revert: Caused ash_content_unittests failure on linux-chromeos-dbg - https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/linux-chromeos-dbg/7312

Original change's description:
> chromeos: gets more ash_unittests working with single-process mash
> 
> The OverviewButtonTrayTests need to set the keyboard devices *after*
> AshTestBase::SetUp() is called. This is is important in single-process mash
> as Ash is the one creating the Env that the keyboard devices us. In
> non-single-process-mash AshTestSuite is creating the Env these tests use.
> 
> The case ShellTest2.DontCrashWhenWindowDeleted is exercising is different
> enough for single-process mash that I created a separate test.
> 
> Adding NOPRESUBMIT=true as this bot passed the trybots, and we're ok with
> this test including Env::GetInstance().
> 
> NOPRESUBMIT=true
> 
> BUG=847992
> TEST=test only changes
> 
> Change-Id: I0543db96ca9aa910340360d8da3e6aafcda34d7f
> Reviewed-on: https://chromium-review.googlesource.com/1174978
> Commit-Queue: Scott Violet <sky@chromium.org>
> Reviewed-by: James Cook <jamescook@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#583161}

TBR=jamescook@chromium.org,sky@chromium.org

Change-Id: Ib23d73ef909ac7fe2c9821d7ca8203228bd7fb4a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 847992
Reviewed-on: https://chromium-review.googlesource.com/1174493
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583197}
2 files changed