Change Link to List in FunctionSignature.

tests/compiler/dart2js/type_substitution_test.dart

Index: tests/compiler/dart2js/type_substitution_test.dart
diff --git a/tests/compiler/dart2js/type_substitution_test.dart b/tests/compiler/dart2js/type_substitution_test.dart
index b166c1b396be9f125a2a07beacc130ecebda4e00..17a4b14196df83519eb9599175a935088251fb61 100644
--- a/tests/compiler/dart2js/type_substitution_test.dart
+++ b/tests/compiler/dart2js/type_substitution_test.dart
@@ -30,7 +30,7 @@ DartType getType(compiler, String name) {
     return signature.type.returnType;
   } else {
     // Otherwise use the first argument type.
-    return signature.requiredParameters.head.computeType(compiler);
+    return signature.requiredParameters.first.type;
   }
 }