ozone: Fix build of events_unittests.

BUG=none
R=spang@chromium.org

Review URL: https://codereview.chromium.org/151733002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248252 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248252