Fix CSS clashing on the Network Themes page.

props SergeyBiryukov.
see #26517 for trunk.

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git-svn-id: http://core.svn.wordpress.org/trunk@26800 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Adjust widths of toolbar items at mobile sizes for better fitting on narrow screens. Fixes toolbar wrapping when using multisite.

props iammattthomas.
see #26537 for trunk.

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git-svn-id: http://core.svn.wordpress.org/trunk@26801 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Themes: Search the theme's slug too.

props matveb.
see #26730 for trunk.

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git-svn-id: http://core.svn.wordpress.org/trunk@26802 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Keyboard navigation friendliness for themes.php.

props matveb, azaozz, jorbin.
see #26527.

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git-svn-id: http://core.svn.wordpress.org/trunk@26803 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix another CSS clashing on the Network Themes page.

props SergeyBiryukov.
see #26513 for trunk.
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git-svn-id: http://core.svn.wordpress.org/trunk@26804 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Pass the $user_id to the `admin_color_scheme_picker` hook for context. props nacin. see #26607 for trunk.

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git-svn-id: http://core.svn.wordpress.org/trunk@26805 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Dashicons: Update to the latest dashicons files.

props empireoflight, melchoyce.
see #26518 for trunk.
Built from https://develop.svn.wordpress.org/trunk@26925


git-svn-id: http://core.svn.wordpress.org/trunk@26806 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Uploads: Fix the Order of Operations for wp_mkdir_p() which caused this branch to never be hit. Props fboender. Fixes #26781 for trunk. See #25822

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