Revert to Immersive Fullscreen on OSX for a special case

If the user is using multiple monitors and turned off "Separate Space
in Each Display", use Immersive Fullscreen so that the other monitors
won't blank out.

BUG=582944,580843

Review URL: https://codereview.chromium.org/1725643002

Cr-Commit-Position: refs/heads/master@{#377116}
1 file changed