mac: Don't let background tab highlight bleed into tabstrip border.

BUG=133565
TEST=Let mehmet@ look at the next canary

Review URL: https://chromiumcodereview.appspot.com/10574036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@143179 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed