Created by Jerry Wang, last modified on Jan 18, 2015
Set the breakpoint to the following two lines and they will be triggered once you perform navigation in UI:
The variable I in line 2457 contains navigation target:
拿到navigation target的ID：
fire一个navigation事件，source和target信息存放在变量n里：
然后就call renderManager开始绘制navigation target的UI：
