Adjusted lib_2/mirrors/initializing_formals_test.dart to match new rule
for static checking on type annotations of initializing formals.
Added language_2/initializing_formals_type_annotation_test.dart to
check the 4 main situations directly.
Change-Id: Icf763c79c99274645f7967b8c3e3a3c3f6536763
Reviewed-on: https://dart-review.googlesource.com/7268
Reviewed-by: Ben Konyi <bkonyi@google.com>
Commit-Queue: Erik Ernst <eernst@google.com>