widget: Add a frameclock_connected boolean

... and use it to not connect anything to the frameclock if it isn't
set.

This gets around the problem that the frame clock is disconnected before
GtkWidgetClass.unrealize() is called but the widget is still marked as
realized and the frame clock is available during the vfunc, which makes
calls like gtk_widget_queue_resize() reconnect to the frame clock.

Closes #168

gtk/gtkcontainer.c

@@ -2087,6 +2087,9 @@ gtk_container_start_idle_sizer (GtkContainer *container)
   if (clock == NULL)
     return;
 
+  if (!GTK_WIDGET (container)->priv->frameclock_connected)
+    return;
+
   container->priv->resize_clock = clock;
   container->priv->resize_handler = g_signal_connect (clock, "layout",
 						      G_CALLBACK (gtk_container_idle_sizer), container);

gtk/gtkwidget.c

@@ -5297,7 +5297,7 @@ gtk_widget_add_tick_callback (GtkWidget       *widget,
 
   priv = widget->priv;
 
-  if (priv->realized && !priv->clock_tick_id)
+  if (priv->frameclock_connected && !priv->clock_tick_id)
     {
       frame_clock = gtk_widget_get_frame_clock (widget);
 
@@ -5368,6 +5368,8 @@ gtk_widget_connect_frame_clock (GtkWidget     *widget,
 {
   GtkWidgetPrivate *priv = widget->priv;
 
+  priv->frameclock_connected = TRUE;
+
   if (GTK_IS_CONTAINER (widget))
     _gtk_container_maybe_start_idle_sizer (GTK_CONTAINER (widget));
 
@@ -5403,6 +5405,8 @@ gtk_widget_disconnect_frame_clock (GtkWidget     *widget,
       gdk_frame_clock_end_updating (frame_clock);
     }
 
+  priv->frameclock_connected = FALSE;
+
   if (priv->context)
     gtk_style_context_set_frame_clock (priv->context, NULL);
 }

gtk/gtkwidgetprivate.h

@@ -89,6 +89,7 @@ struct _GtkWidgetPrivate
   guint hexpand_set           : 1; /* whether to use application-forced  */
   guint vexpand_set           : 1; /* instead of computing from children */
   guint has_tooltip           : 1;
+  guint frameclock_connected  : 1;
 
   /* SizeGroup related flags */
   guint have_size_groups      : 1;