Add a `create_wp_error` action which is called when a `WP_Error` instance is created. Fixes #28319. Props ebinnion
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git-svn-id: http://core.svn.wordpress.org/trunk@28821 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Customizer info section:

* Only show the theme info when doing a live preview of another theme.
* Replace with helper text about what you are customizing and what the Customizer is for.
* Fix focus styling.

props celloexpressions, westonruter. fixes #28550.

Built from https://develop.svn.wordpress.org/trunk@29034


git-svn-id: http://core.svn.wordpress.org/trunk@28822 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Customizer panels:

* Close all accordion sections when going in and out of panels.
* Fix panel positioning when top-level Customizer controls are scrolled down.
* Keyboard accessibility: only focus on visible elements and transfer between them as needed when navigating around panels.

props celloexpressions. see #27406.

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git-svn-id: http://core.svn.wordpress.org/trunk@28823 1a063a9b-81f0-0310-95a4-ce76da25c4cd
accordion.js:

* Remove remnants from when some corners were rounded.
* Docs.

props celloexpressions. see #27406.

Built from https://develop.svn.wordpress.org/trunk@29036


git-svn-id: http://core.svn.wordpress.org/trunk@28824 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add `@see` reference for `set_post_thumbnail()` in the phpDoc for `wp_ajax_set_attachment_thumbnail()`.

See #27891.

Built from https://develop.svn.wordpress.org/trunk@29037


git-svn-id: http://core.svn.wordpress.org/trunk@28825 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE wpView: remove leftover/unused bits, see #28567.
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git-svn-id: http://core.svn.wordpress.org/trunk@28826 1a063a9b-81f0-0310-95a4-ce76da25c4cd