Merge branch 'wip/jimmac/headerbar-specialcasing' into 'master'

Adwaita: specialcase switches and scales for headerbars

Closes #3504

See merge request GNOME/gtk!3043

gtk/theme/Adwaita/_common.scss

@@ -2350,6 +2350,8 @@ switch {
 
   @include focus-ring($offset: 0, $outer: true);
 
+  headerbar & { background-color: darken($dark_fill,8%); } //3504
+
   &:checked {
     color: $selected_fg_color;
     border-color: $switch_borders_color;
@@ -2547,6 +2549,8 @@ treeview.view radio:selected { &:focus, & { @extend %radio; }} // This is a work
   border-radius: 3px;
   background-color: $dark_fill;
 
+  headerbar & { background-color: darken($dark_fill,8%); } //3504
+
   &:disabled {
    background-color: $insensitive_bg_color;
    border-color: $insensitive_borders_color;