Relax kses rules to allow setting playsinline attributes in Video elements.

[youknowriad]

the playsinline attribute is a recent HTML attribute that is very important for mobile devices to allow playing (and auto-playing) videos inline.

The block editor allows setting that attribute for a long time now in the video block but it went unnoticed that this attribute was stripped ​https://github.com/WordPress/gutenberg/pull/14500

In this PR ​https://github.com/WordPress/gutenberg/pull/22346 we're also adding that attribute to the Cover block to fix video backgrounds on mobile.

An extra php filter is added to "override" the limitation for the cover block and that code needs to be removed once the Kses rules are relaxed.

[peterwilsoncc]

Yep, happy if this goes in to the allowed attributes of the video element.

While video support is expanded is there any other attributes that you think are likely to need support in Gutenberg?

[youknowriad]

Thanks, @peterwilsoncc I tried asking around and it doesn't seem like we need another attribute right now.

https://core.trac.wordpress.org/ticket/50167#comment:3

[peterwilsoncc]

In 50167.2.diff​:

• Adds support for the attribute
• Adds unit tests for video element so I could test the attribute.

[peterwilsoncc]

In 47837:

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.

[youknowriad]

Thanks for handling this ticket @peterwilsoncc