[gtk+] mir: fix type warning

[William Hua <williamhua src gnome org>]

commit 3c2aefddd40485852055d21e892962df0b479fa3
Author: William Hua <william hua canonical com>
Date:   Mon Dec 5 11:06:32 2016 -0500

    mir: fix type warning

 gdk/mir/gdkmirdisplay.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gdk/mir/gdkmirdisplay.c b/gdk/mir/gdkmirdisplay.c
index a2ff6ec..77fa665 100644
--- a/gdk/mir/gdkmirdisplay.c
+++ b/gdk/mir/gdkmirdisplay.c
@@ -691,7 +691,7 @@ gdk_mir_display_make_gl_context_current (GdkDisplay   *display,
   mir_context = GDK_MIR_GL_CONTEXT (context);
   window = gdk_gl_context_get_window (context);
 
-  if (mir_context->is_attached || gdk_draw_context_is_drawing (context))
+  if (mir_context->is_attached || gdk_draw_context_is_drawing (GDK_DRAW_CONTEXT (context)))
     {
       egl_surface = _gdk_mir_window_get_egl_surface (window,
                                                      mir_context->egl_config);