Fix many bugs with closure conversion in checked mode.

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

Index: pkg/kernel/testcases/closures/for_variable_capture_test.dart.expect
diff --git a/pkg/kernel/testcases/closures/for_variable_capture_test.dart.expect b/pkg/kernel/testcases/closures/for_variable_capture_test.dart.expect
index 734f46c56de1b22152b28b9877e433cf50053e32..dd1dffc77b422fd1c3d0b2846c12b13458bbc3db 100644
--- a/pkg/kernel/testcases/closures/for_variable_capture_test.dart.expect
+++ b/pkg/kernel/testcases/closures/for_variable_capture_test.dart.expect
@@ -4,7 +4,7 @@ import self as self;
 static method main() → dynamic {
   dynamic closure;
   {
-    Vector #context = MakeVector(3);
+    dynamic #context = MakeVector(3);
     #context[2] = 0;
     dynamic fn = MakeClosure<() → dynamic>(self::closure#main#function, #context);
     for (; (#context[2]).<(3); #context = CopyVector(#context), #context[2] = (#context[2]).+(1)) {
@@ -17,6 +17,6 @@ static method main() → dynamic {
     throw "Expected 1, but got ${x}.";
   }
 }
-static method closure#main#function(Vector #contextParameter) → dynamic {
+static method closure#main#function(dynamic #contextParameter) → dynamic {
   return #contextParameter[2];
 }