Key message we could find in the source code:
1. after sap.ca.ui.utils.busydialog.requireBusyDialog() is called in application, we can only see the rotating wheel in UI after 1.5 seconds - defined in BUSYDIALOG_TIMEOUT.
2. the requireBusyDialog and releaseBusyDialog must be called in pair. There is private variable _iRequiredCount maintained inside the implementation. When require function is called, _iRequiredCount++; release for _iRequiredCount--.
3. it is obsolete. New application should use sap.m.BusyDialog instead.
test2：将timeout從預設的1500ms改成30000ms:
sap.ca.ui.utils.BUSYDIALOG_TIMEOUT = 30000;
第一個video timeout_1500.wmv: 雖然list和detail的資料都ready了，但是因為ETAG需要10s才能傳回，整個UI被這個ETAG的request造成的busy dialog鎖住了，直到10s後UI才能點選
第二個video是把預設的timeout從1500毫秒改成30秒，即busy dialog不會顯示。從video裡看出UI始終是可操作的，盡管背景的ETAG還沒有回來。