Undo.RestoreSnapshot 恢复快照
static function RestoreSnapshot () : void
Description描述
Restore the snapshot state made with CreateSnapshot.
恢复通过CreateSnapshot制作的快照状态。
This can be used if a change in progress should be canceled; for example if the user presses Escape while dragging something.
当一个持续状态被改变时使用，例如用户拖曳某对象时按下了Escape。
