Media Grid: Add context for "or" in [29296].

see #28851.
Built from https://develop.svn.wordpress.org/trunk@29303


git-svn-id: http://core.svn.wordpress.org/trunk@29085 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Media Grid: Improve dropzone margins when viewport height is <400px.

see #28851.
Built from https://develop.svn.wordpress.org/trunk@29304


git-svn-id: http://core.svn.wordpress.org/trunk@29086 1a063a9b-81f0-0310-95a4-ce76da25c4cd