Addendum to https://codereview.appspot.com/7011048/

BUG=391, chromium:166496, chromium:167187

Landing for jschuh
Original patch: https://codereview.appspot.com/7075044/
Review URL: https://codereview.appspot.com/7190044

git-svn-id: https://angleproject.googlecode.com/svn/branches/dx11proto@1781 736b8ea6-26fd-11df-bfd4-992fa37f6226