Revert [29287] based on design and core team feedback. see #29012.

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Editor: use the `post_edit_form_tag` action to add autocomplete="off" to the whole form on the Add/Edit Post screen in WebKit. Prevents editor problems when the browser's Back button is used. Fixes #28037.
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TinyMCE: don't access the parent window when opening the (iframe based) Help/Keyboard Shortcuts modal. Fixes #20094.
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Add some docs to Customizer JS.

Props ericlewis.
See #29157.

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git-svn-id: http://core.svn.wordpress.org/trunk@29228 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add some docs to Customizer JS.

Props ericlewis.
See #29157.

Built from https://develop.svn.wordpress.org/trunk@29451


git-svn-id: http://core.svn.wordpress.org/trunk@29229 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Media at small screens:
- Show the image details/settings as an overlay.
- Better styling for the frame drop-down.
- Remove the multi-select by default on the Insert frame.
See #27423
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WP_Plugins_List_Table::bulk_actions() method declaration should match WP_List_Table, see [29440].

props imath.
fixes #29148.
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