Remove admin-bar class name from body when admin bar element removed due to excessive CSS

[westonruter]

Themes have styles specific for when the admin bar is shown:

twentyseventeen/style.css
1734:.admin-bar .wp-custom-header-video-button {
3505:	.admin-bar .site-navigation-fixed.navigation-top {
3743:	.admin-bar.twentyseventeen-front-page.has-header-image .custom-header-media,
3744:	.admin-bar.twentyseventeen-front-page.has-header-video .custom-header-media,
3745:	.admin-bar.home.blog.has-header-image .custom-header-media,
3746:	.admin-bar.home.blog.has-header-video .custom-header-media {
4161:	.admin-bar .site-navigation-fixed.navigation-top,
4162:	.admin-bar .site-navigation-hidden.navigation-top {

twentysixteen/style.css
2775:	body:not(.custom-background-image).admin-bar:before {
2981:	body:not(.custom-background-image).admin-bar:before {

twentynineteen/style-rtl.css
3280:.admin-bar .main-navigation .main-menu .menu-item-has-children.off-canvas .sub-menu.expanded-true {
3286:.admin-bar .main-navigation .main-menu .menu-item-has-children.off-canvas .sub-menu.expanded-true .sub-menu.expanded-true {
3291:  .admin-bar .main-navigation .main-menu .menu-item-has-children.off-canvas .sub-menu.expanded-true {
3295:  .admin-bar .main-navigation .main-menu .menu-item-has-children.off-canvas .sub-menu.expanded-true .sub-menu.expanded-true {

twentynineteen/style.css
3280:.admin-bar .main-navigation .main-menu .menu-item-has-children.off-canvas .sub-menu.expanded-true {
3286:.admin-bar .main-navigation .main-menu .menu-item-has-children.off-canvas .sub-menu.expanded-true .sub-menu.expanded-true {
3291:  .admin-bar .main-navigation .main-menu .menu-item-has-children.off-canvas .sub-menu.expanded-true {
3295:  .admin-bar .main-navigation .main-menu .menu-item-has-children.off-canvas .sub-menu.expanded-true .sub-menu.expanded-true {

twentyfourteen/style.css
3571:	.admin-bar.masthead-fixed .site-header {

With #2346 the admin bar is now removed if the admin bar CSS is excessive. However, this removal did not include the removal of the admin-bar class from the body element. The results can be undesirable:

The admin-bar class needs to be removed from the body in addition to the wpadminbar element being removed from the DOM. With that change applied, the result is as expected:

As noted in the comments, it would be nice if the style rules could be removed which have selectors referencing .admin-bar. But this would require doing a second pass at tree shaking, and it doesn't seem worthwhile since the number of styles removed is small.

[amedina]

LGTM!