clients: Maximize window when double touch on title bar

Signed-off-by: Xiong Zhang <xiong.y.zhang@intel.com>
diff --git a/shared/cairo-util.h b/shared/cairo-util.h
index 99c7736..11d11d1 100644
--- a/shared/cairo-util.h
+++ b/shared/cairo-util.h
@@ -218,6 +218,13 @@
 		   uint32_t button, enum frame_button_state state);
 
 void
+frame_double_touch_down(struct frame *frame, void *data, int32_t id,
+			int x, int y);
+
+void
+frame_double_touch_up(struct frame *frame, void *data, int32_t id);
+
+void
 frame_repaint(struct frame *frame, cairo_t *cr);
 
 #endif