Revert 231092 "cc: Enable deadline scheduler by default for unit..."

cc_unitests started flaking often soon after this change.
Another suspected change is r231089, which landed around
the same time.

The failing test is:
LayerTreeHostContextTestCompositeAndReadbackBeforeOutputSurfaceInit.RunMultiThread_DirectRenderer_MainThreadPaint 

> cc: Enable deadline scheduler by default for unit tests
> 
> BUG=310591
> 
> Review URL: https://codereview.chromium.org/43483003

TBR=brianderson@chromium.org

Review URL: https://codereview.chromium.org/45783004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231253 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231253