Sets the number of undo levels for user actions the buffer will track.
If the number of user actions exceeds the limit set by this function, older actions will be discarded.
If max_undo_levels is -1, the undo/redo is unlimited.
If max_undo_levels is 0, the undo/redo is disabled.
| this |
a SourceBuffer. |
| max_undo_levels |
the desired maximum number of undo levels. |