No-JS fallback for the Media Library grid view. props michalzuber. fixes #28830, see #24716.

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git-svn-id: http://core.svn.wordpress.org/trunk@28959 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Make audio and video URLs/embed handlers work in `<iframe>`-sandbox'd MCE views. 

Introduce:
`get_editor_stylesheets()`
`wp_media_mce_styles()`.

See #28905.

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git-svn-id: http://core.svn.wordpress.org/trunk@28960 1a063a9b-81f0-0310-95a4-ce76da25c4cd
`_WP_Editors::editor_settings()` should make use of `get_editor_stylesheets()`.

See #28905.

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git-svn-id: http://core.svn.wordpress.org/trunk@28961 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add a new AJAX action: `parse-media-shortcode`. This async call will replace JS rendering of audio/video/playlist shortcodes.

See #28905.

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git-svn-id: http://core.svn.wordpress.org/trunk@28962 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Simplify creation of audio, video, and playlist MCE views by placing them in iframe sandboxes.

Wins:
* Eliminates duplication of code between PHP and JS
* Views can load JS without messing with TinyMCE and scope
* MEjs doesn't break when it loads a file plugin-mode. This allows any file type the MEjs supports to play in MCE views.
* YouTube now works as the source for video.
* Users can still style the views, editor stylesheets are included in these sandboxes.
* Audio and Video URLs and `[embed]`s are no longer broken.
* Remove the crazy compat code necessary to determine what file types play in what browser.
* Remove unneeded Underscore templates.
* Remove the compat code for playlists.

See #28905.

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git-svn-id: http://core.svn.wordpress.org/trunk@28963 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Editor scrolling: also disable in IE < 9. See #28328.
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git-svn-id: http://core.svn.wordpress.org/trunk@28964 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Thirteen: make small-screen menu accessible to keyboard commands and voice-driven software by using a focusable `button` element rather than `h3` for the toggle element. Fixes #28293, props rclations and obenland.
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git-svn-id: http://core.svn.wordpress.org/trunk@28965 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE wpView: remove unused code, props avryl, see #28595
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git-svn-id: http://core.svn.wordpress.org/trunk@28966 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE wpView:
- Cast off commands targeted to a view except undo, redo, RemoveFormat and mceToggleFormat (bold, italic, etc.).
- Disable the link and unlink buttons when a view is selected.
Props avryl, see #28595
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