barrier: Add a time field to MetaBarrierEvent

This was used in gnome-shell, but last-minute changes and multiple
branch confusion on my part meant the field actually never got added.

https://bugzilla.gnome.org/show_bug.cgi?id=693854

src/core/barrier.c

@@ -331,6 +331,7 @@ meta_barrier_fire_event (MetaBarrier    *barrier,
 
   event->ref_count = 1;
   event->event_id = xevent->eventid;
+  event->time = xevent->time;
   event->dt = xevent->dtime;
 
   event->x = xevent->root_x;

src/meta/barrier.h

@@ -53,6 +53,7 @@ typedef enum {
  * MetaBarrierEvent:
  * @event_id: A unique integer ID identifying a
  * consecutive series of motions at or along the barrier
+ * @time: Server time, in milliseconds
  * @dt: Server time, in milliseconds, since the last event
  * sent for this barrier
  * @x: The cursor X position in screen coordinates
@@ -75,6 +76,7 @@ struct _MetaBarrierEvent {
   /* < public > */
   int event_id;
   int dt;
+  guint32 time;
   double x;
   double y;
   double dx;