Depsgraph: Remove workaround for Blender Internal in viewport

This commit effectively reverts fix T45702 done in 067fe2719a.

Reasoning:

- Blender Internal is being replaced with Eevee, and will be removed entirely
  rather soon.

- All render engines are planned to have own depsgraph, so such threading
  conflicts should no longer be an issue.

- We don't want to spend time on porting workarounds for EOL things to a new
  design. Less code -- faster the work :)

- If such notifications will end up needed for some other cases, we would
  need to re-implement this a more proper depsgraph tagging/flushing and make
  it to work with all copy-on-write datablocks and everything.

source/blender/blenkernel/intern/scene.c

@@ -1562,11 +1562,7 @@ void BKE_scene_graph_update_for_newframe(EvaluationContext *eval_ctx,
 	 * for example, clearing update tags from bmain.
 	 */
 	const float ctime = BKE_scene_frame_get(scene);
-	/* Inform editors we are starting scene update. */
-	DEG_editors_update_pre(bmain, scene, true);
-	/* Keep this first.
-	 * TODO(sergey): Should it be after the editors update?
-	 */
+	/* Keep this first. */
 	BLI_callback_exec(bmain, &scene->id, BLI_CB_EVT_FRAME_CHANGE_PRE);
 	/* Update animated image textures for particles, modifiers, gpu, etc,
 	 * call this at the start so modifiers with textures don't lag 1 frame.

source/blender/depsgraph/DEG_depsgraph.h

@@ -252,16 +252,10 @@ typedef void (*DEG_EditorUpdateIDCb)(struct Main *bmain, struct ID *id);
 typedef void (*DEG_EditorUpdateSceneCb)(struct Main *bmain,
                                         struct Scene *scene,
                                         int updated);
-typedef void (*DEG_EditorUpdateScenePreCb)(struct Main *bmain,
-                                           struct Scene *scene,
-                                           bool time);
 
 /* Set callbacks which are being called when depsgraph changes. */
 void DEG_editors_set_update_cb(DEG_EditorUpdateIDCb id_func,
-                               DEG_EditorUpdateSceneCb scene_func,
-                               DEG_EditorUpdateScenePreCb scene_pre_func);
-
-void DEG_editors_update_pre(struct Main *bmain, struct Scene *scene, bool time);
+                               DEG_EditorUpdateSceneCb scene_func);
 
 #ifdef __cplusplus
 } /* extern "C" */

source/blender/depsgraph/intern/depsgraph.cc

@@ -78,7 +78,6 @@ namespace DEG {
 
 static DEG_EditorUpdateIDCb deg_editor_update_id_cb = NULL;
 static DEG_EditorUpdateSceneCb deg_editor_update_scene_cb = NULL;
-static DEG_EditorUpdateScenePreCb deg_editor_update_scene_pre_cb = NULL;
 
 Depsgraph::Depsgraph()
   : time_source(NULL),
@@ -513,17 +512,8 @@ void DEG_graph_free(Depsgraph *graph)
 
 /* Set callbacks which are being called when depsgraph changes. */
 void DEG_editors_set_update_cb(DEG_EditorUpdateIDCb id_func,
-                               DEG_EditorUpdateSceneCb scene_func,
-                               DEG_EditorUpdateScenePreCb scene_pre_func)
+                               DEG_EditorUpdateSceneCb scene_func)
 {
 	DEG::deg_editor_update_id_cb = id_func;
 	DEG::deg_editor_update_scene_cb = scene_func;
-	DEG::deg_editor_update_scene_pre_cb = scene_pre_func;
-}
-
-void DEG_editors_update_pre(Main *bmain, Scene *scene, bool time)
-{
-	if (DEG::deg_editor_update_scene_pre_cb != NULL) {
-		DEG::deg_editor_update_scene_pre_cb(bmain, scene, time);
-	}
 }

source/blender/editors/include/ED_render.h

@@ -49,7 +49,6 @@ void ED_render_id_flush_update(struct Main *bmain, struct ID *id);
 void ED_render_engine_changed(struct Main *bmain);
 void ED_render_engine_area_exit(struct Main *bmain, struct ScrArea *sa);
 void ED_render_scene_update(struct Main *bmain, struct Scene *scene, int updated);
-void ED_render_scene_update_pre(struct Main *bmain, struct Scene *scene, bool time);
 
 void ED_viewport_render_kill_jobs(struct wmWindowManager *wm, struct Main *bmain, bool free_database);
 struct Scene *ED_render_job_get_scene(const struct bContext *C);

source/blender/editors/render/render_update.c

@@ -163,23 +163,6 @@ void ED_render_scene_update(Main *bmain, Scene *scene, int updated)
 	recursive_check = false;
 }
 
-void ED_render_scene_update_pre(Main *bmain, Scene *scene, bool time)
-{
-	/* Blender internal might access to the data which is gonna to be freed
-	 * by the scene update functions. This applies for example to simulation
-	 * data like smoke and fire.
-	 */
-	if (time && !BKE_scene_use_new_shading_nodes(scene)) {
-		bScreen *sc;
-		ScrArea *sa;
-		for (sc = bmain->screen.first; sc; sc = sc->id.next) {
-			for (sa = sc->areabase.first; sa; sa = sa->next) {
-				ED_render_engine_area_exit(bmain, sa);
-			}
-		}
-	}
-}
-
 void ED_render_engine_area_exit(Main *bmain, ScrArea *sa)
 {
 	/* clear all render engines in this area */

source/blender/windowmanager/intern/wm_init_exit.c

@@ -178,8 +178,7 @@ void WM_init(bContext *C, int argc, const char **argv)
 	BKE_blender_callback_test_break_set(wm_window_testbreak); /* blender.c */
 	BKE_spacedata_callback_id_remap_set(ED_spacedata_id_remap); /* screen.c */
 	DEG_editors_set_update_cb(ED_render_id_flush_update,
-	                          ED_render_scene_update,
-	                          ED_render_scene_update_pre);
+	                          ED_render_scene_update);
 	
 	ED_spacetypes_init();   /* editors/space_api/spacetype.c */