gtk3: Apply primary-toolbar styling to its child toolbars

Some applications (at least recent versions of Synaptic Package
Manager) have a toolbar widget inside a .primary-toolbar box.

This didn't work properly with the Arc-Darker variant, which has
light toolbar and dark .primary-toolbar, but resulted in mismatching
foreground and background colors, and possibly other oddities.

Fixes: #51

common/gtk-3.0/3.20/sass/_common.scss

@@ -975,17 +975,19 @@ toolbar {
 }
 
 .primary-toolbar:not(.libreoffice-toolbar) {  // LO messes up the toolbar styling, so exclude LO toolbars
-  color: $header_fg;
-  background-color: opacify($header_bg, 1);
-  box-shadow: none;
-  border-width: 0 0 1px 0;
-  border-style: solid;
-  border-image: linear-gradient(to bottom, opacify($header_bg, 1),
-                                           darken($header_bg, 7%)) 1 0 1 0; //temporary hack for rhythmbox 3.1
+  &, & toolbar {
+    color: $header_fg;
+    background-color: opacify($header_bg, 1);
+    box-shadow: none;
+    border-width: 0 0 1px 0;
+    border-style: solid;
+    border-image: linear-gradient(to bottom, opacify($header_bg, 1),
+                                             darken($header_bg, 7%)) 1 0 1 0; //temporary hack for rhythmbox 3.1
 
-  //&:backdrop { background-color: opacify($header_bg_backdrop, 1); }
+    //&:backdrop { background-color: opacify($header_bg_backdrop, 1); }
 
-  separator { @extend %header_separator; }
+    separator { @extend %header_separator; }
+  }
 }
 
 .primary-toolbar { @extend %header_widgets; }

common/gtk-3.0/3.22/sass/_common.scss

@@ -1001,17 +1001,19 @@ toolbar {
 }
 
 .primary-toolbar:not(.libreoffice-toolbar) {  // LO messes up the toolbar styling, so exclude LO toolbars
-  color: $header_fg;
-  background-color: opacify($header_bg, 1);
-  box-shadow: none;
-  border-width: 0 0 1px 0;
-  border-style: solid;
-  border-image: linear-gradient(to bottom, opacify($header_bg, 1),
-                                           darken($header_bg, 7%)) 1 0 1 0; //temporary hack for rhythmbox 3.1
+  &, & toolbar {
+    color: $header_fg;
+    background-color: opacify($header_bg, 1);
+    box-shadow: none;
+    border-width: 0 0 1px 0;
+    border-style: solid;
+    border-image: linear-gradient(to bottom, opacify($header_bg, 1),
+                                             darken($header_bg, 7%)) 1 0 1 0; //temporary hack for rhythmbox 3.1
 
-  //&:backdrop { background-color: opacify($header_bg_backdrop, 1); }
+    //&:backdrop { background-color: opacify($header_bg_backdrop, 1); }
 
-  separator { @extend %header_separator; }
+    separator { @extend %header_separator; }
+  }
 }
 
 .primary-toolbar { @extend %header_widgets; }

common/gtk-3.0/3.24/sass/_common.scss

@@ -1001,17 +1001,19 @@ toolbar {
 }
 
 .primary-toolbar:not(.libreoffice-toolbar) {  // LO messes up the toolbar styling, so exclude LO toolbars
-  color: $header_fg;
-  background-color: opacify($header_bg, 1);
-  box-shadow: none;
-  border-width: 0 0 1px 0;
-  border-style: solid;
-  border-image: linear-gradient(to bottom, opacify($header_bg, 1),
-                                           darken($header_bg, 7%)) 1 0 1 0; //temporary hack for rhythmbox 3.1
+  &, & toolbar {
+    color: $header_fg;
+    background-color: opacify($header_bg, 1);
+    box-shadow: none;
+    border-width: 0 0 1px 0;
+    border-style: solid;
+    border-image: linear-gradient(to bottom, opacify($header_bg, 1),
+                                             darken($header_bg, 7%)) 1 0 1 0; //temporary hack for rhythmbox 3.1
 
-  //&:backdrop { background-color: opacify($header_bg_backdrop, 1); }
+    //&:backdrop { background-color: opacify($header_bg_backdrop, 1); }
 
-  separator { @extend %header_separator; }
+    separator { @extend %header_separator; }
+  }
 }
 
 .primary-toolbar { @extend %header_widgets; }