Fix T61575: missing Cycles viewport updates when changing settings.

This reverts "Depsgraph: Don't tag original IDs", commit:
5f814cb3b4.

source/blender/depsgraph/intern/depsgraph_tag.cc

@@ -280,6 +280,7 @@ void depsgraph_tag_component(Depsgraph *graph,
 		ComponentNode *cow_comp =
 		        id_node->find_component(NodeType::COPY_ON_WRITE);
 		cow_comp->tag_update(graph, update_source);
+		id_node->id_orig->recalc |= ID_RECALC_COPY_ON_WRITE;
 	}
 }
 
@@ -765,6 +766,7 @@ static void deg_graph_clear_id_node_func(
 	DEG::Depsgraph *deg_graph = reinterpret_cast<DEG::Depsgraph *>(data_v);
 	DEG::IDNode *id_node = deg_graph->id_nodes[i];
 	id_node->id_cow->recalc &= ~ID_RECALC_ALL;
+	id_node->id_orig->recalc &= ~ID_RECALC_ALL;
 
 	/* Clear embedded node trees too. */
 	bNodeTree *ntree_cow = ntreeFromID(id_node->id_cow);

source/blender/depsgraph/intern/eval/deg_eval_copy_on_write.cc

@@ -684,6 +684,7 @@ ID *deg_expand_copy_on_write_datablock(const Depsgraph *depsgraph,
 {
 	const ID *id_orig = id_node->id_orig;
 	ID *id_cow = id_node->id_cow;
+	const int id_cow_recalc = id_cow->recalc;
 	/* No need to expand such datablocks, their copied ID is same as original
 	 * one already. */
 	if (!deg_copy_on_write_is_needed(id_orig)) {
@@ -760,6 +761,7 @@ ID *deg_expand_copy_on_write_datablock(const Depsgraph *depsgraph,
 	/* Correct or tweak some pointers which are not taken care by foreach
 	 * from above. */
 	update_special_pointers(depsgraph, id_orig, id_cow);
+	id_cow->recalc = id_orig->recalc | id_cow_recalc;
 	return id_cow;
 }
 

source/blender/depsgraph/intern/eval/deg_eval_flush.cc

@@ -248,6 +248,10 @@ void flush_editors_id_update(Main *bmain,
 		/* TODO(sergey): Do we need to pass original or evaluated ID here? */
 		ID *id_orig = id_node->id_orig;
 		ID *id_cow = id_node->id_cow;
+		/* Copy tag from original data to CoW storage.
+		 * This is because DEG_id_tag_update() sets tags on original
+		 * data. */
+		id_cow->recalc |= (id_orig->recalc & ID_RECALC_ALL);
 		/* Gather recalc flags from all changed components. */
 		GHASH_FOREACH_BEGIN(ComponentNode *, comp_node, id_node->components)
 		{