Minor stylistic cleanup in flutter_tools/lib/src/dart/summary.dart (#6788)
Minor stylistic cleanup in flutter_tools/lib/src/dart/summary.dart (#6788)

I was in here trying to figure out why we rebuild sky_services (the
answer is, because we rebuild every package we've ever downloaded, but
that's not really a problem for new users so whatever), and while I
was here I did some cleanup.
flutter/flutter,tvolkert/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,tvolkert/flutter,turnidge/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,cbracken/flutter,flutter/flutter,turnidge/flutter,Hixie/flutter,Hixie/flutter,tvolkert/flutter,flutter/flutter,Hixie/flutter,turnidge/flutter,Hixie/flutter,cbracken/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,turnidge/flutter,Hixie/flutter,Hixie/flutter,cbracken/flutter,flutter/flutter,flutter/flutter,Hixie/flutter,flutter/flutter,turnidge/flutter,tvolkert/flutter,tvolkert/flutter,cbracken/flutter,cbracken/flutter,tvolkert/flutter,flutter/flutter,tvolkert/flutter