[rAc OSX] Add support for drawing borders around dialog notifications.

BUG=286528
TEST=Top notification in Wallet mode (i.e. when signed in) should have a subtle
     darker gray border.
R=groby@chromium.org

Review URL: https://codereview.chromium.org/55973003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232981 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232981
- Updating unittests to conform to Ozone interface change.
 - Updating unittests to conform to Compositor constructor change.

BUG=

Review URL: https://codereview.chromium.org/57803004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232982 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232982