Revert of Remove ash_unittests to see if it's affecting bot stability...

Revert of Remove ash_unittests to see if it's affecting bot stability (https://codereview.chromium.org/411673002/)

Reason for revert:
Was not the cause of flakiness.

Original issue's description:
> Remove ash_unittests to see if it's affecting bot stability
> 
> Bot has been completely failing intermittently. ash_unittests
> is the Win8-specific part that runs here, so temporarily remove
> it to see if it's related to the back-and-forth to Metro
> switches.
> 
> BUG=340422
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=284820

TBR=sky@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=340422

Review URL: https://codereview.chromium.org/414783002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284993 0039d316-1c4b-4281-b951-d872f2087c98

testing/buildbot/chromium.win.json

@@ -333,6 +333,7 @@
       "views_unittests",
       "wm_unittests",
       "aura_unittests",
+      "ash_unittests",
       "compositor_unittests",
       "events_unittests"
     ]