KSES: Support the video element's playsinline attribute.

Allow users without the `unfiltered_html` capability to use the `playsinline` attribute when embedding videos.

Additionally this adds unit tests for passing the video element through kses.

Fixes #50167. See #29826.


git-svn-id: https://develop.svn.wordpress.org/trunk@47837 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/kses.php

@@ -397,15 +397,16 @@ if ( ! CUSTOM_TAGS ) {
 		),
 		'var'        => array(),
 		'video'      => array(
-			'autoplay' => true,
-			'controls' => true,
-			'height'   => true,
-			'loop'     => true,
-			'muted'    => true,
-			'poster'   => true,
-			'preload'  => true,
-			'src'      => true,
-			'width'    => true,
+			'autoplay'    => true,
+			'controls'    => true,
+			'height'      => true,
+			'loop'        => true,
+			'muted'       => true,
+			'playsinline' => true,
+			'poster'      => true,
+			'preload'     => true,
+			'src'         => true,
+			'width'       => true,
 		),
 	);