Eliminate an optimization that caused an event not to fire.

OnUpdate wasn't getting called if there was no reparenting or component update
work to do -- but ProBuilder needs it even if it's just about meshes getting
updated.

Author: Benoit Hudson

Assets/FbxExporters/FbxPrefab.cs

@@ -907,21 +907,18 @@ void CompareAndUpdate()
             // First write down what we want to do.
             var updates = new UpdateList(GetFbxHistory(), m_fbxModel.transform, this);
 
-            // If we don't need to do anything, jump out now.
-            if (!updates.NeedsUpdates()) {
-                Log("{0}: no updates needed", transform.name);
-                return;
-            }
-
-            // We want to do something, so instantiate the prefab, work on the instance, then copy back.
+            // Instantiate the prefab, work on the instance, then copy back.
+            // We could optimize this out if we had nothing to do, but then the
+            // OnUpdate handler wouldn't always get called, and that makes for
+            // confusing API.
             var prefabInstance = UnityEditor.PrefabUtility.InstantiatePrefab(this.gameObject) as GameObject;
             if (!prefabInstance) {
                 throw new System.Exception(string.Format("Failed to instantiate {0}; is it really a prefab?",
                             this.gameObject));
             }
             var fbxPrefabInstance = prefabInstance.GetComponent<FbxPrefab>();
 
-            // Do ALL the things!
+            // Do ALL the things (potentially nothing).
             var updatedObjects = updates.ImplementUpdates(fbxPrefabInstance);
 
             // Tell listeners about it. They're free to make adjustments now.