Add per-scene UndoRedo

editor/plugins/gradient_texture_2d_editor_plugin.h

@@ -34,6 +34,8 @@
 #include "editor/editor_plugin.h"
 #include "editor/editor_spin_slider.h"
 
+class EditorUndoRedoManager;
+
 class GradientTexture2DEditorRect : public Control {
 	GDCLASS(GradientTexture2DEditorRect, Control);
 
@@ -44,7 +46,7 @@ class GradientTexture2DEditorRect : public Control {
 	};
 
 	Ref<GradientTexture2D> texture;
-	UndoRedo *undo_redo = nullptr;
+	Ref<EditorUndoRedoManager> undo_redo;
 	bool snap_enabled = false;
 	float snap_size = 0;
 
@@ -74,7 +76,7 @@ class GradientTexture2DEditor : public VBoxContainer {
 	GDCLASS(GradientTexture2DEditor, VBoxContainer);
 
 	Ref<GradientTexture2D> texture;
-	UndoRedo *undo_redo = nullptr;
+	Ref<EditorUndoRedoManager> undo_redo;
 
 	Button *reverse_button = nullptr;
 	Button *snap_button = nullptr;