[Backport] Do not check GTK+ dependencies when use_ozone is defined.

Author: "joone.hur@intel.com"

glib is not included in ozone platform:
https://codereview.chromium.org/249583003

Therefore, we do not need to check GTK+ dependencies when use_ozone is defined.

Review URL: https://codereview.chromium.org/272743002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269373
Merge pull request #159 from pozdnyakov/backport_269373

[Backport] Do not check GTK+ dependencies when use_ozone is defined.