Insert implicit downcasts in kernel strong mode.

pkg/kernel/testcases/closures/capture_closure.dart.expect

Index: pkg/kernel/testcases/closures/capture_closure.dart.expect
diff --git a/pkg/kernel/testcases/closures/capture_closure.dart.expect b/pkg/kernel/testcases/closures/capture_closure.dart.expect
index dae8d72a0a31f9010f9fda8cf8ef9b829f4c933c..115cb6b89c5958fba786208affe24c8d3c26c395 100644
--- a/pkg/kernel/testcases/closures/capture_closure.dart.expect
+++ b/pkg/kernel/testcases/closures/capture_closure.dart.expect
@@ -31,6 +31,6 @@ static method main(dynamic arguments) → dynamic {
   final mock::Context #context = new mock::Context::•(1);
   #context.parent = null;
   #context.[]=(0, new self::Closure#main#f::•(#context));
-  final dynamic g = new self::Closure#main#g::•(#context);
+  final() → dynamic g = new self::Closure#main#g::•(#context);

[Kevin Millikin (Google), 2017/01/11 12:00:58]

It looks like a space should be between 'final' and '('.

[asgerf, 2017/01/11 12:15:12]

I've fixed the text printer to ensure a space before function types.

However, the closure tests now fail internally due to some changes in the
verifier, so I couldn't regenerate the expectations. I've reverted the changes
to this file.

   g.call();
 }