spinner: Active spinners should be :checked, not :active

If that sounds confusing, it's because GTK and CSS can sometimes not
agree on naming.

:active for CSS means that a button is currently pressed on an element.
And that is clearly not the case for spinning spinners.

gtk/gtkspinner.c

@@ -252,10 +252,10 @@ gtk_spinner_set_active (GtkSpinner *spinner,
 
       if (active)
         gtk_widget_set_state_flags (GTK_WIDGET (spinner),
-                                    GTK_STATE_FLAG_ACTIVE, FALSE);
+                                    GTK_STATE_FLAG_CHECKED, FALSE);
       else
         gtk_widget_unset_state_flags (GTK_WIDGET (spinner),
-                                      GTK_STATE_FLAG_ACTIVE);
+                                      GTK_STATE_FLAG_CHECKED);
     }
 }
 

gtk/theme/Adwaita/_common.scss

@@ -214,7 +214,7 @@ spinner {
   background: none;
   opacity: 0; // non spinning spinner makes no sense
   -gtk-icon-source: -gtk-icontheme('process-working-symbolic');
-  &:active {
+  &:checked {
     opacity: 1;
     animation: spin 1s linear infinite;
     &:insensitive {

gtk/theme/HighContrast/_common.scss

@@ -167,7 +167,7 @@ spinner {
   background-color: blue;
   opacity: 0; // non spinning spinner makes no sense
   -gtk-icon-source: -gtk-icontheme('process-working-symbolic');
-  &:active {
+  &:checked {
     opacity: 1;
     animation: spin 1s linear infinite;
     &:insensitive {