Currently, DefaultKeyboardFocusManager.dispatchEvent(..) for WINDOW_LOST_FOCUS doesn't take into acount the source object of the event.
Instead, it considers current global focused window to be the window losing focus. The reason of such behavior is that the platform-dependent
code posts WINDOW_LOST_FOCUS to an owner frame/dialog when it loses activation, while some of its owned window is actually a focused window.
We have to revise this logic and see if we can always post WINDOW_LOST_FOCUS to an appropriate window.