Commit Graph

3114 Commits

Author SHA1 Message Date
Weston Ruter 5aec57b209 Customize: Fix navigation of site in preview on IE11.
Addresses issue in IE11 where the default port number of `:80` is unexpectedly included on `link.host` for links dynamically created by scripts.

Props westonruter, afercia for testing.
See #38409.
Fixes #40198.

Built from https://develop.svn.wordpress.org/trunk@40318


git-svn-id: http://core.svn.wordpress.org/trunk@40225 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-03-23 17:25:43 +00:00
Andrea Fercia c3a2b57241 Media: Restore correct upload errors displaying after [37610].
Props codegeass, MatheusGimenez, joemcgill.
Fixes #39516.

Built from https://develop.svn.wordpress.org/trunk@40126


git-svn-id: http://core.svn.wordpress.org/trunk@40063 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-26 18:15:43 +00:00
Andrew Ozz 9c1d14b875 TinyMCE: preserve empty image alt attributes.
Props afercia.
Fixes #39912 for trunk.
Built from https://develop.svn.wordpress.org/trunk@40110


git-svn-id: http://core.svn.wordpress.org/trunk@40047 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-24 20:41:43 +00:00
Weston Ruter 0343f50561 Customize: Prevent vertical clipping of thumbnail in header image customizer control.
Removes some method overrides on `wp.customize.HeaderTool.ChoiceView` introduced in [27497].

See #21785.
Props bradyvercher.
Fixes #38559.

Built from https://develop.svn.wordpress.org/trunk@40082


git-svn-id: http://core.svn.wordpress.org/trunk@40019 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-20 00:10:49 +00:00
Adam Silverstein c7b217cee9 JavaScript: when starting Backbone history, stop if previously started.
Prevent a potential error condition if Backbone history is started by a plugin or theme before core tries to start it. 

Props tfrommen.
Fixes #39612.

Built from https://develop.svn.wordpress.org/trunk@40076


git-svn-id: http://core.svn.wordpress.org/trunk@40013 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-17 22:00:42 +00:00
Adam Silverstein 518ff1576b REST API: JavaScript client - improve route discovery for custom namespaces.
Fix parsing of custom namespace routes. Transform class names, removing dashes and capitalizing each word/route part so a route path of `widgets/recent-posts` becomes a collection with the name `WidgetsRecentPosts`. Correct parent route part when routes are longer than expected, reversing parse direction.

Props westonruter, jazbek.
Fixes #39561.

Built from https://develop.svn.wordpress.org/trunk@40074


git-svn-id: http://core.svn.wordpress.org/trunk@40011 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-17 20:54:44 +00:00
Weston Ruter 34b179876e Customize: Skip intercepting non-HTTP(S) links in customizer preview just as jump links are ignored.
Ensures that links with `javascript:`, `mailto:` and other protocols work as expected in the customizer preview.

Fixes #39797.

Built from https://develop.svn.wordpress.org/trunk@40064


git-svn-id: http://core.svn.wordpress.org/trunk@40001 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-16 21:21:45 +00:00
Adam Silverstein e322b0eb77 Media: debounce the media grid search, avoiding duplicate requests.
Add a debounce wrapper to the media grid search handler. The search callback is now fired after a 300 ms typing pause.

Remove redundant handlers for 'search' and 'change', preventing multiple/duplicate search callbacks.

Props certainstrings, joemcgill, Kelderic, batmoo.
Fixes #38911.

Built from https://develop.svn.wordpress.org/trunk@40060


git-svn-id: http://core.svn.wordpress.org/trunk@39997 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-15 17:29:44 +00:00
Weston Ruter f3644a702e Customize: Ensure edit shortcuts get re-created for nested partials when a parent partial is refreshed.
Fixes issue where the edit shortcut for a nav menu gets dropped when the containing Custom Menu widget is updated.

See #39101.
Fixes #39353.

Built from https://develop.svn.wordpress.org/trunk@40055


git-svn-id: http://core.svn.wordpress.org/trunk@39992 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-11 03:35:43 +00:00
Andrea Fercia d33301821b Buttons: Improve the `.button-link` CSS class for link-like buttons.
Updates `.button-link` adding color and underline to make link-like buttons look
like links by default. Introduces `.button-link-delete` as a modifier, stackable
CSS class for red button-links.

Props Cheffheid, afercia.

See #34242.
Fixes #35126.

Built from https://develop.svn.wordpress.org/trunk@40052


git-svn-id: http://core.svn.wordpress.org/trunk@39989 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-09 16:47:44 +00:00
Scott Taylor 9bf3844ef9 Media: in `wp.media.view.DeleteSelectedPermanentlyButton`, move destructive async operations outside of the `selection` loop.
Fixes #39780.

Built from https://develop.svn.wordpress.org/trunk@40051


git-svn-id: http://core.svn.wordpress.org/trunk@39988 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-08 19:44:41 +00:00
Scott Taylor 907e8cbd66 Media: in `wp.media.view.Toolbar.refresh()`, check for a selection before iterating over models.
Props chandrapatel.
Fixes #39511.

Built from https://develop.svn.wordpress.org/trunk@40050


git-svn-id: http://core.svn.wordpress.org/trunk@39987 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-08 19:17:43 +00:00
Adam Silverstein 717aeab3cc REST API: JavaScript client should use `_.extend` when merging objects.
Correct an issue during the client's dynamic route discovery in `wp.api.utils.decorateFromRoute` where `_.union` potentially failed if used on objects.

Props ketuchetan.
Fixes #39341.


Built from https://develop.svn.wordpress.org/trunk@40040


git-svn-id: http://core.svn.wordpress.org/trunk@39977 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-02-03 21:46:43 +00:00
Andrea Fercia 4ca4ff999a Accessibility: Make the inline uploader button a real button.
See `wp.media.view.UploaderWindow`.

Fixes #39305.

Built from https://develop.svn.wordpress.org/trunk@40021


git-svn-id: http://core.svn.wordpress.org/trunk@39958 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-01-27 18:32:41 +00:00
Andrew Ozz 69c29935d5 TinyMCE: improve the previews for embedded WordPress posts:
- Add option to force a sandbox iframe in wpview.
- Use it to show the embedded post preview.
- Remove the deprecated `wpembed` plugin.js

Fixes #39513.
Built from https://develop.svn.wordpress.org/trunk@40019


git-svn-id: http://core.svn.wordpress.org/trunk@39956 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-01-27 04:25:44 +00:00
Andrew Ozz 66a39611f6 TinyMCE: strip browser inserted `<u>` and <font>` tags from inside links when copying and pasting in IE and Edge.
Fixes #39570.
Built from https://develop.svn.wordpress.org/trunk@39916


git-svn-id: http://core.svn.wordpress.org/trunk@39853 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-01-17 01:25:44 +00:00
Andrew Ozz 82a8065f70 TinyMCE: ensure the inline toolbar is shown and properly positioned when there are several wpview blocks in the editor and the user selects one after the other.
Props gitlost.
Fixes #38849.
Built from https://develop.svn.wordpress.org/trunk@39910


git-svn-id: http://core.svn.wordpress.org/trunk@39847 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-01-16 00:22:43 +00:00
Andrew Ozz 35c91b7c0d TinyMCE: prevent the inline toolbar from appearing on partially selected wpview nodes. This can happen when HTML is initially loaded in the editor and wpview is the first node, or sometimes on repeatedly pasting the same wpview.
Props gitlost.
Fixes #38849.
Built from https://develop.svn.wordpress.org/trunk@39904


git-svn-id: http://core.svn.wordpress.org/trunk@39841 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-01-15 03:00:43 +00:00
Andrew Ozz 45f3ee380c TinyMCE: when inserting a wpview, place the caret after is so the user can continue typing without interruption.
Props iseulde.
Fixes #39337.
Built from https://develop.svn.wordpress.org/trunk@39903


git-svn-id: http://core.svn.wordpress.org/trunk@39840 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-01-15 02:41:40 +00:00
Andrew Ozz 90f441e1b4 TinyMCE: improve removal of spaces from empty paragraphs when loading HTML in the editor.
Fixes #39437.
Built from https://develop.svn.wordpress.org/trunk@39902


git-svn-id: http://core.svn.wordpress.org/trunk@39839 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-01-15 02:06:41 +00:00
Adam Silverstein c8a3496ebe REST API: Add error handling for fetch error in `buildModelGetter` of wp-api.js.
When a call to a model getter method fails, reject the returned deferred object. Enables better handling of fetch errors.

Props westonruter, adamsilverstein.
Fixes #39314.

Built from https://develop.svn.wordpress.org/trunk@39680


git-svn-id: http://core.svn.wordpress.org/trunk@39620 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2017-01-05 03:03:42 +00:00
Weston Ruter f7ba137f19 Customize: Fix visible edit shortcuts for `wp_nav_menu()` instances using the `menu` arg (such as in the Custom Menu widget) instead of the `theme_location` arg.
Also fix logic for `focus-control-for-setting` handler to focus on the first control (lowest `priority` value) associated with a given setting instead of the last control encountered when iterating over all controls, as this ensures the first control in a `nav_menu` section is focused rather than the last one.

Props westonruter, sirbrillig.
See #27403.
Fixes #39101.

Built from https://develop.svn.wordpress.org/trunk@39622


git-svn-id: http://core.svn.wordpress.org/trunk@39562 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-20 22:05:43 +00:00
Adam Silverstein bc7a03a33b WP-API: JavaScript client - fix setup of models used by wp.api.collections objects.
Correct setup for the `model` attribute of `wp.api.collections` objects. Set the collection model as a function that returns a new model of the underlying type, instead of setting it as the model prototype. Fixes an issue where models for fetched collections weren't set up properly and didn't have the expected mixin methods such as `getCategories` available.

Props jesseenterprises.
Fixes #39070.

Built from https://develop.svn.wordpress.org/trunk@39603


git-svn-id: http://core.svn.wordpress.org/trunk@39543 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-15 12:54:42 +00:00
Ella Iseulde Van Dorpe 4ec102c189 Editor: Remove target=_blank when unchecked in the link modal.
Fixes #39276 for trunk.


Built from https://develop.svn.wordpress.org/trunk@39601


git-svn-id: http://core.svn.wordpress.org/trunk@39541 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-14 20:30:44 +00:00
Gary Pendergast 7d9b5b14b5 Libraries: Update zxcvbn from version 1.0 to 4.4.1
This includes masses of bug fixes, as well as tweaks to how passwords are scored.

QUnit tests have been updated to reflect tha scoring changes.

Full changelog: https://github.com/dropbox/zxcvbn/compare/v1.0...v4.4.1

Fixes #31647.


Built from https://develop.svn.wordpress.org/trunk@39596


git-svn-id: http://core.svn.wordpress.org/trunk@39536 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-13 11:23:42 +00:00
Weston Ruter c9b863fc40 Customize: Prevent navigation in preview when clicking on child elements of preview links that have non-previewable URLs.
Fixes #39098.

Built from https://develop.svn.wordpress.org/trunk@39584


git-svn-id: http://core.svn.wordpress.org/trunk@39524 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-12 08:09:41 +00:00
Weston Ruter 8a89a50c69 Customize: Prevent edit shortcut from losing event handler after selective refresh.
Props sirbrillig.
See #27403.
Fixes #39100.

Built from https://develop.svn.wordpress.org/trunk@39581


git-svn-id: http://core.svn.wordpress.org/trunk@39521 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-12 07:52:43 +00:00
Weston Ruter 9669c60397 Customize: Fix ability to shift-click on placeholder/pre-saved nav menu items in preview to focus on corresponding control.
Fixes #39102.

Built from https://develop.svn.wordpress.org/trunk@39562


git-svn-id: http://core.svn.wordpress.org/trunk@39502 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-10 23:47:41 +00:00
Weston Ruter d10cde75c6 Customize: Allow (optional) `url` parameter to be omitted in intercepted calls to `history.pushState()` and `history.replaceState()` in customize preview.
Fixes issue where calls without the `url` parameter erroneously end up rewriting the location path to `/undefined`.

Props Christian1012, westonruter.
Fixes #39175.

Built from https://develop.svn.wordpress.org/trunk@39547


git-svn-id: http://core.svn.wordpress.org/trunk@39487 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-09 01:59:41 +00:00
Weston Ruter 672b8a61cd Customize: Prevent infinite full refresh from occurring when selective refresh falls back for a nav menu that has items excluded from rendering via filtering.
See #37032.
Fixes #38612.

Built from https://develop.svn.wordpress.org/trunk@39510


git-svn-id: http://core.svn.wordpress.org/trunk@39450 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-06 02:51:42 +00:00
Andrew Nacin 0d983eb0ef Build/Test Tools: Specify exact node version in package.json.
Enforce it in the tests.

see #35105.

Built from https://develop.svn.wordpress.org/trunk@39478


git-svn-id: http://core.svn.wordpress.org/trunk@39418 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-04 17:32:16 +00:00
Weston Ruter 0a31089bf6 Customize: Ensure a `custom_css` post insertion gets an initial post revision.
Props georgestephanis, westonruter.
See #30854, #38672, #35395.
Fixes #39032.

Built from https://develop.svn.wordpress.org/trunk@39477


git-svn-id: http://core.svn.wordpress.org/trunk@39417 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-12-04 17:31:33 +00:00
Helen Hou-Sandí 844b0a5307 Trunk is really 4.8-alpha now.
Built from https://develop.svn.wordpress.org/trunk@39359


git-svn-id: http://core.svn.wordpress.org/trunk@39299 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-29 04:55:50 +00:00
Pascal Birchler 98e8bf7ba2 Embeds: Correctly remove security attribute from iframes in IE 10 and IE 11.
This was originally added in 4.4, but presumably broke with [35708], which prevented these browsers from actually reaching the relevant code section.
Let's make embeds work again in IE 10 and IE 11.

Fixes #38694.
Built from https://develop.svn.wordpress.org/trunk@39347


git-svn-id: http://core.svn.wordpress.org/trunk@39287 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-23 13:38:33 +00:00
Weston Ruter 6b5d960453 Customize: Clean up docs and code style for customize changes in 4.7.
* Adds missing `resolve`/`fail` for promise returned by `loadThemePreview`.
* Adds missing jsdoc blocks and tags.
* Adds missing phpdoc and makes corrections.

See #37770.
Fixes #38908.

Built from https://develop.svn.wordpress.org/trunk@39345


git-svn-id: http://core.svn.wordpress.org/trunk@39285 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-23 06:05:32 +00:00
Joe Hoyle e20ded7e75 REST API: Make JS Client store schema in session storage.
Props adamsilverstein.
Fixes #38895.
Built from https://develop.svn.wordpress.org/trunk@39344


git-svn-id: http://core.svn.wordpress.org/trunk@39284 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-23 02:55:30 +00:00
Andrew Ozz 9925a4ebb5 TinyMCE: avoid calling `editor.focus()` on loading the content in the editor. It may trigger scroll-into-view in the browser. Call the quirks fix in TinyMCE directly.
Props gitlost.
Fixes #38511.
Built from https://develop.svn.wordpress.org/trunk@39334


git-svn-id: http://core.svn.wordpress.org/trunk@39274 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-21 20:15:31 +00:00
Weston Ruter 277d4d0ab0 Customize: Prevent selective refresh from causing infinite fallback refreshes when nav menu contains invalid items.
Invalid nav menu items are exported as settings in the customize controls since it `is_admin()`, but any such `nav_menu_item` settings are excluded from the preview since it's the frontend. Selective refresh for nav menus needs to ignore the syncing of any such `nav_menu_item` settings that are `_invalid` since they are never rendered, and when a nav menu only contains invalid items, an infinite fallback refresh can ensue.

Fixes #38890.

Built from https://develop.svn.wordpress.org/trunk@39333


git-svn-id: http://core.svn.wordpress.org/trunk@39273 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-21 19:16:32 +00:00
Weston Ruter 3284f9a989 Customize: Remove iframe-specific behaviors from customize preview when previewing on frontend and not contained inside iframe.
* Strip out `customize_messenger_channel` from preview window URL when not contained in iframe.
* Allow interacting with unpreviewable links and forms when previewing customized state on frontend.

See #30937.
Fixes #38867.

Built from https://develop.svn.wordpress.org/trunk@39332


git-svn-id: http://core.svn.wordpress.org/trunk@39272 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-21 16:56:30 +00:00
Gary Pendergast c04452a81f Emoji: Update Twemoji fallback to version 2.2.2.
This removes support for the skin tone modifier on emoji involving two or more people. This functionality is opposed by Apple and Google, so there is unlikely to be an input mechanism for such emoji, they oppose it on the grounds that they "...do not think a mechanism should be supported that only permits depiction of multi-person groups (or elements) in which each person has the same skin tone."

See their official notification for further details: http://www.unicode.org/L2/L2016/16332-remove-multi-emb.pdf

This change does not require a CDN update, as no emoji were altered or added, only removed.

See #38113.


Built from https://develop.svn.wordpress.org/trunk@39319


git-svn-id: http://core.svn.wordpress.org/trunk@39259 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-19 11:05:32 +00:00
Ella Iseulde Van Dorpe a003a7f1bb TinyMCE: fix automatic scroll on page load.
Set focus when new content is loaded in the editor, but not when it's the initial load.

Fixes #38511.


Built from https://develop.svn.wordpress.org/trunk@39299


git-svn-id: http://core.svn.wordpress.org/trunk@39239 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-18 20:38:31 +00:00
Ella Iseulde Van Dorpe 32b3a7f772 TinyMCE: remove extra space in tooltip.
This prevents wrapping and looks better, even though there seems to be some space between the other control key characters.

See #38063.


Built from https://develop.svn.wordpress.org/trunk@39284


git-svn-id: http://core.svn.wordpress.org/trunk@39224 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-17 23:59:30 +00:00
Ella Iseulde Van Dorpe 79b3576650 TinyMCE views: fix Firefox issues.
* Set focus before rendering to prevent reload in Firefox.
* Rerender views if they are unloaded.
* Remove timeout added in [29513].
* Fix argument in wp.mce.views.render.
* Empty views on hide. Missed in #36434.

Props gitlost, azaozz, iseulde.
Fixes #38511.


Built from https://develop.svn.wordpress.org/trunk@39282


git-svn-id: http://core.svn.wordpress.org/trunk@39222 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-17 20:32:32 +00:00
Sergey Biryukov 2fadd7a895 Docs: Use 3-digit, x.x.x style semantic versioning for `@since 4.7.0` entries.
See #37770.
Built from https://develop.svn.wordpress.org/trunk@39281


git-svn-id: http://core.svn.wordpress.org/trunk@39221 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-17 18:28:30 +00:00
Andrea Fercia 5c86bfd201 Small coding standards cleanup of wp-custom-header.js.
Small coding standards cleanup of wp-custom-header.js after [39272].

Built from https://develop.svn.wordpress.org/trunk@39277


git-svn-id: http://core.svn.wordpress.org/trunk@39217 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-17 09:04:31 +00:00
Joe McGill 5ef714db18 Themes: Improve a11y and extendability of custom video headers.
This adds play/pause controls to video headers, along with voice
assistance, using `wp.a11y.speak`, to make custom video headers more
accessible. To make styling the play/pause button easier for themes,
CSS has been omitted from the default implementation.

This also includes a refactor of the `wp.customHeader` code to introduce
a `BaseHandler` class, which can be extended by plugins and themes to modify
or enhance the default video handlers.

Props davidakennedy, afercia, bradyvercher, joemcgill, adamsilverstein, rianrietveld.
Fixes #38678.
Built from https://develop.svn.wordpress.org/trunk@39272


git-svn-id: http://core.svn.wordpress.org/trunk@39212 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-16 23:26:31 +00:00
Weston Ruter 4664f80711 Customize: Prevent edit shortcut buttons from being inserted into container elements in the `head` or into elements which should not get interactive children.
See #27403, #38672.
Fixes #38830.

Built from https://develop.svn.wordpress.org/trunk@39270


git-svn-id: http://core.svn.wordpress.org/trunk@39210 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-16 20:37:30 +00:00
Sergey Biryukov a45e419926 Text Changes: Unify permission error message in `wp-ajax-response.js`.
See #34521.
Built from https://develop.svn.wordpress.org/trunk@39253


git-svn-id: http://core.svn.wordpress.org/trunk@39193 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-15 20:42:30 +00:00
Andrew Ozz 0c2b137a60 TinyMCE: fix black outline around `_moz_abspos`. This is added in Firefox in paragraphs inserted after a non-editable block.
See #38757.
Built from https://develop.svn.wordpress.org/trunk@39217


git-svn-id: http://core.svn.wordpress.org/trunk@39157 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-14 02:34:31 +00:00
Weston Ruter e5b82c250f Customize: Improve extensibility of Custom CSS.
* Add `customize_value_custom_css` filter to `WP_Customize_Custom_CSS::value()` method.
* Introduce `customize_update_custom_css_post_content_args` filter in `WP_Customize_Custom_CSS::update()` method.
* Make clear that `wp_get_custom_css()` and `wp_get_custom_css` filter are specifically for obtaining the value to render/display. Eliminate use of `wp_get_custom_css()` when getting the setting value. Use the underlying `post_value` directly when `is_previewed`.
* Move anonymous functions handing JS previewing for `custom_logo`, `custom_css`, and `background` into named functions on the `wp.customize.settingPreviewHandlers` to allow plugins to override/extend preview logic.
* Update `_custom_background_cb` to always print a `style` tag wen in the customizer preview, and update background preview logic to replace existing style element instead of appending a new style to the head so that background changes don't unexpectedly override any Custom CSS in the preview's stylesheet cascade.

Props westonruter, georgestephanis.
See #22058.
Fixes #38672.

Built from https://develop.svn.wordpress.org/trunk@39209


git-svn-id: http://core.svn.wordpress.org/trunk@39149 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2016-11-13 02:43:29 +00:00