Try to keep function-typed parameters parameter lists with the parameter name.

I can't repro the original issue in #58, so other nested list changes likely took
care of that, but this addresses the other comments on that bug.

Fixes #58.

BUG=https://github.com/dart-lang/dart_style/issues/58
R=kevmoo@google.com

Review URL: https://chromiumcodereview.appspot.com//830543002