cogl/frame-info: Stop passing the CoglOutput

It's unused, and if it would be, it'd be unreliable, as it'd only be
valid on the Xlib and GLX cogl backends.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1289

cogl/cogl/cogl-frame-info-private.h

@@ -43,8 +43,6 @@ struct _CoglFrameInfo
   float refresh_rate;
 
   int64_t global_frame_counter;
-
-  CoglOutput *output;
 };
 
 CoglFrameInfo *_cogl_frame_info_new (void);

cogl/cogl/cogl-frame-info.c

@@ -72,12 +72,6 @@ cogl_frame_info_get_refresh_rate (CoglFrameInfo *info)
   return info->refresh_rate;
 }
 
-CoglOutput *
-cogl_frame_info_get_output (CoglFrameInfo *info)
-{
-  return info->output;
-}
-
 int64_t
 cogl_frame_info_get_global_frame_counter (CoglFrameInfo *info)
 {

cogl/cogl/cogl-frame-info.h

@@ -126,20 +126,6 @@ int64_t cogl_frame_info_get_presentation_time (CoglFrameInfo *info);
 COGL_EXPORT
 float cogl_frame_info_get_refresh_rate (CoglFrameInfo *info);
 
-/**
- * cogl_frame_info_get_output:
- * @info: a #CoglFrameInfo object
- *
- * Gets the #CoglOutput that the swapped frame was presented to.
- *
- * Return value: (transfer none): The #CoglOutput that the frame was
- *        presented to, or %NULL if this could not be determined.
- * Since: 1.14
- * Stability: unstable
- */
-COGL_EXPORT CoglOutput *
-cogl_frame_info_get_output (CoglFrameInfo *info);
-
 /**
  * cogl_frame_info_get_global_frame_counter: (skip)
  */

cogl/cogl/winsys/cogl-winsys-glx.c

@@ -1662,8 +1662,6 @@ set_frame_info_output (CoglOnscreen *onscreen,
 {
   CoglFrameInfo *info = g_queue_peek_tail (&onscreen->pending_frame_infos);
 
-  info->output = output;
-
   if (output)
     {
       float refresh_rate = cogl_output_get_refresh_rate (output);