Simplify fullscreen exit bubble on mac; updating always creates one freshly.

This also moved the logic for when NOT to display the bubble to a single
location, fixing 129456.

BUG=129456
TEST=Manually, see bug.

Review URL: https://chromiumcodereview.appspot.com/10573003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@143397 0039d316-1c4b-4281-b951-d872f2087c98
4 files changed