DFW: Properly handle Esc key when the content is focused or when switching browser tabs.

props avryl.
fixes #28279.
Built from https://develop.svn.wordpress.org/trunk@28443


git-svn-id: http://core.svn.wordpress.org/trunk@28270 1a063a9b-81f0-0310-95a4-ce76da25c4cd