Fix build on Fedora 20.

The build broke because atk_focus_tracker_notify is deprecated since ATK
2.9.4 and Chromium builds with warnings set as errors.

BUG=298815

Review URL: https://codereview.chromium.org/25166002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225895 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225895