The ScrollDirection argument needs a default all the way through.
The ScrollDirection argument needs a default all the way through.

Fixes the Stocks crash on startup.

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