Tests that $0 works with shadow dom.
'Author shadow element: ' + $0.id = 'Author shadow element: shadow'
'User agent shadow host: ' + $0.id = 'User agent shadow host: user-agent-host'
Tests that $0 works with shadow dom.
'Author shadow element: ' + $0.id = 'Author shadow element: shadow'
'User agent shadow host: ' + $0.id = 'User agent shadow host: user-agent-host'