Revert 228975 "Disable AcceleratorControllerTest.ControllerConte..."

Underlying bug fixed.

> Disable AcceleratorControllerTest.ControllerContext on win aura
> due to flakiness.
> 
> TBR=cpu@chromium.org
> BUG=297650
> 
> Review URL: https://codereview.chromium.org/27493003

TBR=tim@chromium.org

Review URL: https://codereview.chromium.org/66903003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233930 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233930