[web-fixit] Use generic types in control-flow-collections tests

Use generic types in type tests. This causes types to be retained.

Fixes:

language/control_flow_collections/if_inference_test
language/control_flow_collections/map_set_ambiguity_test

Change-Id: Ie8fe93320ec623cc3812d43bd36550a0fe32f613
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/338424
Commit-Queue: Stephen Adams <sra@google.com>
Reviewed-by: Bob Nystrom <rnystrom@google.com>
diff --git a/tests/language/control_flow_collections/utils.dart b/tests/language/control_flow_collections/utils.dart
index c8e5dc8..4a810c9 100644
--- a/tests/language/control_flow_collections/utils.dart
+++ b/tests/language/control_flow_collections/utils.dart
@@ -95,15 +95,18 @@
 
 void expectListOf<T>(Object object) {
   Expect.type<List>(object);
+  Expect.type<List<T>>(object);
   _expectTypeArguments(T.toString(), object);
 }
 
 void expectSetOf<T>(Object object) {
   Expect.type<Set>(object);
+  Expect.type<Set<T>>(object);
   _expectTypeArguments(T.toString(), object);
 }
 
 void expectMapOf<K, V>(Object object) {
   Expect.type<Map>(object);
+  Expect.type<Map<K, V>>(object);
   _expectTypeArguments("$K, $V", object);
 }