Add ID attribute to style element from wp_add_inline_style().

props westonruter.
fixes #30032.

git-svn-id: https://develop.svn.wordpress.org/trunk@29956 602fd350-edb4-49c9-b593-d223f7449a82
Themes: Make "Live Preview" the primary action and "Activate" secondary.

props celloexpressions.
fixes #26899.

git-svn-id: https://develop.svn.wordpress.org/trunk@29957 602fd350-edb4-49c9-b593-d223f7449a82
wp_add_inline_style():
* Change the `wp-inline-style-$handle` class added in [29956] to `$handle-inline-css` for consistency with existing patterns.
* Add the ID attribute when concatenation is enabled as well.

props georgestephanis.
see #30032.

git-svn-id: https://develop.svn.wordpress.org/trunk@29958 602fd350-edb4-49c9-b593-d223f7449a82