cairo-util: Draw solid titlebar for frames with only buttons

Previously geometry was changed to leave space for titlebar if a frame
has only buttons but no title. This patch fixes theme_render_frame to
avoid transparent titlebar.

Signed-off-by: Boyan Ding <stu_dby@126.com>
diff --git a/shared/cairo-util.h b/shared/cairo-util.h
index 4493b0d..fb25c34 100644
--- a/shared/cairo-util.h
+++ b/shared/cairo-util.h
@@ -26,6 +26,8 @@
 #include <stdint.h>
 #include <cairo.h>
 
+#include <wayland-util.h>
+
 void
 surface_flush_device(cairo_surface_t *surface);
 
@@ -69,7 +71,8 @@
 void
 theme_render_frame(struct theme *t, 
 		   cairo_t *cr, int width, int height,
-		   const char *title, uint32_t flags);
+		   const char *title, struct wl_list *buttons,
+		   uint32_t flags);
 
 enum theme_location {
 	THEME_LOCATION_INTERIOR = 0,