Previously:
- if the object is currently not frozen, we called
g_object_notify_queue_freeze() once. Afterwards dispatch the event
directly. This is probably the common case, and requires one
notify_lock lock.
- if the object is currently frozen, we call
g_object_notify_queue_freeze(), g_object_notify_queue_add().
g_object_notify_queue_thaw().
This required taking the notify_lock three times.
- if the object is currently not frozen and in_init, then we called
g_object_notify_queue_freeze(), g_object_notify_queue_freeze(),
g_object_notify_queue_add(). This also required to take
the lock three times. There is another thaw at the end of
object initialization.
That was because we first call g_object_notify_queue_freeze() to see
whether we are frozen. And depending on that, queue the event (and thaw
again).
Instead, g_object_notify_queue_add() can do the check and queueing in
one step. There is no need to call a freeze() to (conditionally) enqueue
a notification. Now only one lock is taken in all cases.
Also, g_object_notify_queue_freeze() and g_object_notify_queue_thaw()
both call g_datalist_id_get_data() (which also take a bit lock). As the
thaw is no longer necessary, the second lock is also saved.