Revert "chromeos: add SingleProcessMash mode"

This reverts commit b092ae622b9ab3856d64d3eca543e4ecb243be77.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 582411 as the
culprit for failures in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyRAsSDVdmU3VzcGVjdGVkQ0wiMWNocm9taXVtL2IwOTJhZTYyMmI5YWIzODU2ZDY0ZDNlY2E1NDNlNGVjYjI0M2JlNzcM

Sample Failed Build: https://ci.chromium.org/buildbot/chromium.chromiumos/linux-chromeos-dbg/7241

Sample Failed Step: ash_content_unittests

Original change's description:
> chromeos: add SingleProcessMash mode
> 
> This makes Ash create an Env if passed SingleProcessMash. In addition this
> makes all window creation go through a factory that ensures the right env is
> supplied.
> 
> See https://docs.google.com/document/d/11ha_KioDdXe4iZS2AML1foKnCJlNKm7Q1hFr6VW8dV4/edit
> for more details.
> 
> This also adds the feature to ui/base.
> 
> BUG=847992
> TEST=covered by tests
> 
> Change-Id: Ica3c433627222f0e076dddaf19b1ab09168cebeb
> Reviewed-on: https://chromium-review.googlesource.com/1168282
> Commit-Queue: Scott Violet <sky@chromium.org>
> Reviewed-by: James Cook <jamescook@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#582411}

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
BUG=847992

Change-Id: I9e2e3c0d92dc7b51f08fa35a2dfacd5ca8af57f2
Reviewed-on: https://chromium-review.googlesource.com/1171706
Cr-Commit-Position: refs/heads/master@{#582427}
89 files changed