[mutter] Don't create the Cogl GLib source multiple times

[Owen Taylor <otaylor src gnome org>]

commit d6b290ef77d855137dfd8a48795f8b49d0ee554b
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Wed Jun 29 17:03:46 2016 -0400

    Don't create the Cogl GLib source multiple times
    
    Since the check for backend->cogl_context was accidentally moved
    to clutter_backend_do_real_create_context, the Glib source that
    is created at the end of clutter_backend_do_create_context() is
    created and added each time create_context() is called, though
    create_context() is supposed to be idempotent.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=768243

 clutter/clutter/clutter-backend.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/clutter/clutter/clutter-backend.c b/clutter/clutter/clutter-backend.c
index a25ff91..b512d70 100644
--- a/clutter/clutter/clutter-backend.c
+++ b/clutter/clutter/clutter-backend.c
@@ -230,9 +230,6 @@ clutter_backend_do_real_create_context (ClutterBackend  *backend,
   CoglSwapChain *swap_chain;
   GError *internal_error;
 
-  if (backend->cogl_context != NULL)
-    return TRUE;
-
   klass = CLUTTER_BACKEND_GET_CLASS (backend);
 
   swap_chain = NULL;
@@ -361,6 +358,9 @@ clutter_backend_real_create_context (ClutterBackend  *backend,
   gboolean allow_any;
   int i;
 
+  if (backend->cogl_context != NULL)
+    return TRUE;
+
   if (allowed_drivers == NULL)
     allowed_drivers = CLUTTER_DRIVERS;