file: /base/packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
function: addStatusBarWindow()
use:
- hide status bar with height as 0
- show status bar with height as getStatusBarHeight()
fix black bar in top when hide statusbar
xml: /base/core/res/res/values/dimens.xml
change line status_bar_height 25dip => 0dip