* Used now in core to facilitate displaying inserted media. See #40854.
* The `[embed]` shortcode is not supported because there is no post context for caching oEmbed responses. This depends on #34115.
* Add `do_shortcode()` to the `widget_text_content` filter in the same way it is added for `the_content` at priority 11, with `shortcode_unautop()` called at priority 10 after `wpautop()`.
* For Text widget in legacy mode, manually apply `do_shortcode()` (and `shortcode_unautop()` if auto-paragraph checked) if the core-added `widget_text_content` filter remains, unless a plugin added `do_shortcode()` to `widget_text` to prevent applying shortcodes twice.
* Ensure that global `$post` is `null` while filters apply in the Text widget so shortcode handlers won't run with unexpected contexts.
Props westonruter, nacin, aaroncampbell.
See #40854, #34115.
Fixes#10457.
Built from https://develop.svn.wordpress.org/trunk@41361
git-svn-id: http://core.svn.wordpress.org/trunk@41194 1a063a9b-81f0-0310-95a4-ce76da25c4cd
84d2c51153