[gtk/master-fix-minimize] Fix minimize button on border-less windows, see #2345

[Alex Samorukov <asamorukov src gnome org>]

commit b09ea5610d20e9c4958f140929a3a96bfc4c24c5
Author: Alex Samorukov <samm net-art cz>
Date:   Sat Jan 4 12:18:54 2020 +0000

    Fix minimize button on border-less windows, see #2345

 gdk/quartz/gdksurface-quartz.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/gdk/quartz/gdksurface-quartz.c b/gdk/quartz/gdksurface-quartz.c
index 7600edda08..9797984b06 100644
--- a/gdk/quartz/gdksurface-quartz.c
+++ b/gdk/quartz/gdksurface-quartz.c
@@ -795,7 +795,8 @@ _gdk_quartz_display_create_surface_impl (GdkDisplay    *display,
 
         if (window->surface_type == GDK_SURFACE_TEMP)
           {
-            style_mask = NSBorderlessWindowMask;
+            /* without NSMiniaturizableWindowMask window will not minimize */
+            style_mask = NSBorderlessWindowMask | NSMiniaturizableWindowMask;
           }
         else
           {