GUI 間の空間縦方向に使用されるデフォルトの高さを取得します。
When creating GUI without GUILayout, such as is for instance required by PropertyDrawers, and you need to place several controls under each other, you can use standardVerticalSpacing to ensure there's the proper standard spacing between the controls. This is advisable over hardcoding specific pixel values. See Also: EditorGUILayout.GetControlRect.