Cannot view source only for ActivityThread type errors, can for all other java/android problems

Why is it that I cannot view the source for errors coming from the ActivityThread such as these:

ActivityThread.performLaunchActivity(ActivityThread$ActivityClientRecord, Intent)开发者_StackOverflow line: 1768    
ActivityThread.handleLaunchActivity(ActivityThread$ActivityClientRecord, Intent) line: 1784 
ActivityThread.access$1500(ActivityThread, ActivityThread$ActivityClientRecord, Intent) line: 123   
ActivityThread$H.handleMessage(Message) line: 939

But I can view the source for all other Android & java errors?

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you can attach the android platform source to eclipse, here is the blog instruction with screenshot even! http://android.opensourceror.org/2010/01/18/android-source/