Fix Mac resolution bug.

This was broken by https://codereview.chromium.org/54273006.

BUG=339639

Review URL: https://codereview.chromium.org/138213010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248113 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248113