Widget Customizer: Make the available widgets panel a Backbone view.

see #27690.
Built from https://develop.svn.wordpress.org/trunk@27986


git-svn-id: http://core.svn.wordpress.org/trunk@27816 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Browsers other than Firefox need a timeout when parsing audio and video shortcodes into MCE views.

See [27655].


Built from https://develop.svn.wordpress.org/trunk@27987


git-svn-id: http://core.svn.wordpress.org/trunk@27817 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Widget Customizer: Cleanup `wp.customize.Widgets.WidgetControl`.

see #27690.
Built from https://develop.svn.wordpress.org/trunk@27988


git-svn-id: http://core.svn.wordpress.org/trunk@27818 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Update Dashicons.

New icons: `.dashicons-external`, `.dashicons-editor-contract` and `.dashicons-universal-access-alt`.
Updated icons: `.dashicons-code`, `.dashicons-universal-access`, `.dashicons-arrow-x-alt` and `.dashicons-arrow-x-alt2`.
Restores also `.dashicons-post-trash` as an alias for `.dashicons-trash`, which is the new one.

props melchoyce, empireoflight.
see #26936.
Built from https://develop.svn.wordpress.org/trunk@27989


git-svn-id: http://core.svn.wordpress.org/trunk@27819 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Avoid stomping of bulk postdata inside the bulk_edit_posts() loop.

props kovshenin.
see [27964], see #27452.

Built from https://develop.svn.wordpress.org/trunk@27990


git-svn-id: http://core.svn.wordpress.org/trunk@27820 1a063a9b-81f0-0310-95a4-ce76da25c4cd