Testing Mouse Event for Safari

Safari fails to catch MouseEvent.MOUSE_UP outside the stage.   After the pointer is moved outside the stage with the mouse button pressed then the button is released outside the stage, Safari seems to give up watching the mouse.

Safariではステージ外のMouseEvent.MOUSE_UPイベントが受取れない。マウスボタンを押したままポインタをステージ外に出すして放すと、マウスイベントを見なくなるようだ。