Make type system changes backwards compatible

pkg/analyzer/test/src/task/strong_mode_test.dart

Index: pkg/analyzer/test/src/task/strong_mode_test.dart
diff --git a/pkg/analyzer/test/src/task/strong_mode_test.dart b/pkg/analyzer/test/src/task/strong_mode_test.dart
index 16c3058937f00e87dee87a3965f77ff17f5df801..79e4472a25cd9fc7ef3a5fd0cdaf2cb898a4e2b8 100644
--- a/pkg/analyzer/test/src/task/strong_mode_test.dart
+++ b/pkg/analyzer/test/src/task/strong_mode_test.dart
@@ -25,7 +25,8 @@ main() {
 @reflectiveTest
 class InstanceMemberInferrerTest extends AbstractContextTest {
   InstanceMemberInferrer get createInferrer =>
-      new InstanceMemberInferrer(context.typeProvider, context.typeSystem);
+      new InstanceMemberInferrer(context.typeProvider,
+          typeSystem: context.typeSystem);
 
   /**
    * Add a source with the given [content] and return the result of resolving