Adwaita: make selection on infobars visible

see https://bugzilla.gnome.org/show_bug.cgi?id=745622

gtk/theme/Adwaita/_common.scss

@@ -3899,7 +3899,7 @@ infobar { border-style: none; }
     }
   }
 
-  label:selected { &:focus, &:hover, & { background-color: darken($selected_bg_color, 10%); }}
+  selection { background-color: darken($selected_bg_color, 10%); }
 
   *:link { @extend %link_selected; }
 }

gtk/theme/Adwaita/gtk-contained-dark.css

@@ -4365,16 +4365,10 @@ infobar {
         .error button:backdrop:disabled label,
         .error button:backdrop:disabled {
           color: #6f91b4; }
-  .info label:selected:focus, .info label:selected:hover, .info label:selected,
-  .question label:selected:focus,
-  .question label:selected:hover,
-  .question label:selected,
-  .warning label:selected:focus,
-  .warning label:selected:hover,
-  .warning label:selected,
-  .error label:selected:focus,
-  .error label:selected:hover,
-  .error label:selected {
+  .info selection,
+  .question selection,
+  .warning selection,
+  .error selection {
     background-color: #184472; }
 
 /************

gtk/theme/Adwaita/gtk-contained.css

@@ -4394,16 +4394,10 @@ infobar {
         .error button:backdrop:disabled label,
         .error button:backdrop:disabled {
           color: #9bc2ea; }
-  .info label:selected:focus, .info label:selected:hover, .info label:selected,
-  .question label:selected:focus,
-  .question label:selected:hover,
-  .question label:selected,
-  .warning label:selected:focus,
-  .warning label:selected:hover,
-  .warning label:selected,
-  .error label:selected:focus,
-  .error label:selected:hover,
-  .error label:selected {
+  .info selection,
+  .question selection,
+  .warning selection,
+  .error selection {
     background-color: #2a76c6; }
 
 /************