layer: Add an API to get the total duration of the layer

API:
    ges_layer_get_duration

docs/libs/ges-sections.txt

@@ -385,6 +385,7 @@ ges_layer_get_timeline
 ges_layer_get_auto_transition
 ges_layer_set_auto_transition
 ges_layer_is_empty
+ges_layer_get_duration
 
 GES_TIMELINE_GET_LAYERS
 GES_TIMELINE_GET_TRACKS

ges/ges-layer.c

@@ -219,7 +219,7 @@ ges_layer_init (GESLayer * self)
  * ges_layer_resync_priorities:
  * @layer: a #GESLayer
  *
- * Resyncs the priorities of the objects controlled by @layer.
+ * Resyncs the priorities of the clips controlled by @layer.
  * This method
  */
 static gboolean
@@ -285,6 +285,28 @@ new_asset_cb (GESAsset * source, GAsyncResult * res, NewAssetUData * udata)
   g_slice_free (NewAssetUData, udata);
 }
 
+/**
+ * ges_layer_get_duration:
+ * @layer: The #GESLayer to get the duration from
+ *
+ * Lets you retrieve the duration of the layer, which means
+ * the end time of the last clip inside it
+ *
+ * Returns: The duration of a layer
+ */
+GstClockTime
+ges_layer_get_duration (GESLayer * layer)
+{
+  GList *tmp;
+  GstClockTime duration = 0;
+
+  for (tmp = layer->priv->clips_start; tmp; tmp = tmp->next) {
+    duration = MAX (duration, _END (tmp->data));
+  }
+
+  return duration;
+}
+
 /* Public methods */
 /**
  * ges_layer_remove_clip:

ges/ges-layer.h

@@ -124,6 +124,7 @@ void ges_layer_set_auto_transition (GESLayer * layer,
 					     gboolean auto_transition);
 
 GList*   ges_layer_get_clips   (GESLayer * layer);
+GstClockTime ges_layer_get_duration (GESLayer *layer);
 
 G_END_DECLS