Add missing `screen-reader-text` CSS class in [29294].

see #28867.
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git-svn-id: http://core.svn.wordpress.org/trunk@29090 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Revert [28894] as it's currently unused in core.

see #28487.
Built from https://develop.svn.wordpress.org/trunk@29309


git-svn-id: http://core.svn.wordpress.org/trunk@29091 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Replace `is_https_url()` with `'https' === parse_url( $url, PHP_URL_SCHEME )`.

see #28427, #28487.
Built from https://develop.svn.wordpress.org/trunk@29311


git-svn-id: http://core.svn.wordpress.org/trunk@29092 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Media Grid: Improve lazy loading.

props kovshenin.
see #24716.
Built from https://develop.svn.wordpress.org/trunk@29312


git-svn-id: http://core.svn.wordpress.org/trunk@29093 1a063a9b-81f0-0310-95a4-ce76da25c4cd