Avoid infinite loop in syncChildren().
Avoid infinite loop in syncChildren().

This was a typo in #1062.

Also, some minor code cleanup and expose (in the app dump) the
_disqualifiedFromEverAppearingAgain boolean for debugging purposes.

aghassemi/flutter,flutter/flutter,tvolkert/flutter,flutter/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,turnidge/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,jason-simmons/flutter,jason-simmons/flutter,jason-simmons/flutter,Hixie/flutter,cbracken/flutter,Hixie/flutter,aghassemi/flutter,flutter/flutter,cbracken/flutter,Hixie/flutter,flutter/flutter,cbracken/flutter,tvolkert/flutter,jason-simmons/flutter,Hixie/flutter,Hixie/flutter,cbracken/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,aghassemi/flutter,turnidge/flutter,tvolkert/flutter,tvolkert/flutter,tvolkert/flutter,cbracken/flutter,turnidge/flutter,flutter/flutter,turnidge/flutter,flutter/flutter,flutter/flutter,cbracken/flutter,flutter/flutter,aghassemi/flutter,tvolkert/flutter,cbracken/flutter,cbracken/flutter,turnidge/flutter