Preserve type variables in closure conversion.

pkg/kernel/test/closures/suite.dart

 // Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
 library test.kernel.closures.suite;
 
 import 'dart:io' show File;
 
 import 'dart:async' show Future;
 
@@ skipping 42 matching lines @@
           const Verify(true),
           new MatchExpectation(".expect",
               updateExpectations: updateExpectations),
           const WriteDill(),
           const ReadDill(),
           // TODO(29143): add `Run` step when Vectors are added to VM.
           //const Run(),
         ];
 
   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);
   }
 }
 
 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
     extends Step<Program, Program, ClosureConversionContext> {
   const ClosureConversion();
 
   String get name => "closure conversion";
 
   Future<Result<Program>> run(
       Program program, ClosureConversionContext testContext) async {
@@ skipping 23 matching lines @@
           .run(vm.toFilePath(), [generated.path, "Hello, World!"]);
       print(process.output);
       return process.toResult();
     } finally {
       generated.parent.delete(recursive: true);
     }
   }
 }
 
 main(List<String> arguments) => runMe(arguments, createContext, "testing.json");