disable AcceleratorControllerTest.GlobalAcceleratorsToggleAppList on win aura

Failing on Win Aura bots flakily for a few days, and now quite a lot. No
clear regression cause though.

R=kbr@chromium.org
TBR=kbr@chromium.org
BUG=316012

Review URL: https://codereview.chromium.org/63783002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233486 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233486