Widgets: Toggle widget arrow when the widget is closed using Close link.

props senff.
fixes #29617.
Built from https://develop.svn.wordpress.org/trunk@29726


git-svn-id: http://core.svn.wordpress.org/trunk@29500 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Media Frames: Set the box-sizing CSS property to border-box for checkboxes and radio buttons.

props mlteal.
see #29493.
Built from https://develop.svn.wordpress.org/trunk@29727


git-svn-id: http://core.svn.wordpress.org/trunk@29501 1a063a9b-81f0-0310-95a4-ce76da25c4cd