Block library applying width of 100% to iframe

[jeremeylduvall]

In 5.3, there's some styling at wp-includes/css/dist/block-library/style.css that sets the width for iframe elements to 100%. You can see it here:

​https://github.com/WordPress/WordPress/blob/5.3-branch/wp-includes/css/dist/block-library/style.css#L1536

It looks like this may result from this commit to Gutenberg:

​https://github.com/WordPress/gutenberg/commit/5430dced1e3594ca28f5a9c829aa9baac8905e27#diff-fded095b4f7622cd5e81d8193bf2f4b4R162

Should this be set to max-width? The width: 100% setting can cause issues with existing iframes (ad units, for example).

[jeremeylduvall]

cc @joen for input as I believe you authored the original Gutenberg commit referred to above.

[Joen]

Created ​https://github.com/WordPress/gutenberg/pull/18240 to explore a fix for this.