Bug 1645996 - Add explicit namespace qualification for MakeSpan in WidgetStyleCache.

Differential Revision: https://phabricator.services.mozilla.com/D79801

widget/gtk/WidgetStyleCache.cpp

@@ -637,7 +637,7 @@ static void CreateHeaderBarButtons() {
   ButtonLayout buttonLayout[TOOLBAR_BUTTONS];
 
   size_t activeButtons =
-      GetGtkHeaderBarButtonLayout(MakeSpan(buttonLayout), nullptr);
+      GetGtkHeaderBarButtonLayout(mozilla::MakeSpan(buttonLayout), nullptr);
 
   if (IsToolbarButtonEnabled(buttonLayout, activeButtons,
                              MOZ_GTK_HEADER_BAR_BUTTON_MINIMIZE)) {