Preserve type variables in closure conversion.

pkg/kernel/test/closures/suite.dart

Index: pkg/kernel/test/closures/suite.dart
diff --git a/pkg/kernel/test/closures/suite.dart b/pkg/kernel/test/closures/suite.dart
index 9748f3acda9c3c73f959d5f305d6b80d522cca6a..84d288894a026844a690cd6baefd566e593dbaf7 100644
--- a/pkg/kernel/test/closures/suite.dart
+++ b/pkg/kernel/test/closures/suite.dart
@@ -60,8 +60,7 @@ class ClosureConversionContext extends ChainContext implements CompileContext {
         ];
 
   static Future<ClosureConversionContext> create(
-      Chain suite, Map<String, String> environment) async {
-    bool strongMode = environment.containsKey(STRONG_MODE);
+      Chain suite, Map<String, String> environment, bool strongMode) async {
     bool updateExpectations = environment["updateExpectations"] == "true";
     return new ClosureConversionContext(strongMode, updateExpectations);
   }
@@ -69,9 +68,10 @@ class ClosureConversionContext extends ChainContext implements CompileContext {
 
 Future<ClosureConversionContext> createContext(
     Chain suite, Map<String, String> environment) async {
+  bool strongMode = environment.containsKey(STRONG_MODE);
   environment["updateExpectations"] =
       const String.fromEnvironment("updateExpectations");
-  return ClosureConversionContext.create(suite, environment);
+  return ClosureConversionContext.create(suite, environment, strongMode);
 }
 
 class ClosureConversion