Keep types in signatures of function types properly instantiated as the function

runtime/lib/mirrors_impl.dart

Index: runtime/lib/mirrors_impl.dart
diff --git a/runtime/lib/mirrors_impl.dart b/runtime/lib/mirrors_impl.dart
index 4ad2f175d5d4c5d10b11af46ab8ed08eb89c506d..0ba81e8a720fd5e30319a0da05e745bba00b766f 100644
--- a/runtime/lib/mirrors_impl.dart
+++ b/runtime/lib/mirrors_impl.dart
@@ -950,8 +950,8 @@ class _LocalFunctionTypeMirror extends _LocalClassMirror
   TypeMirror _returnType = null;
   TypeMirror get returnType {
     if (_returnType == null) {
-      _returnType = reflectType(
-          _FunctionTypeMirror_return_type(_functionReflectee, _instantiator));
+      _returnType =
+          reflectType(_FunctionTypeMirror_return_type(_functionReflectee));
     }
     return _returnType;
   }
@@ -977,7 +977,7 @@ class _LocalFunctionTypeMirror extends _LocalClassMirror
   MethodMirror _FunctionTypeMirror_call_method(functionReflectee)
       native "FunctionTypeMirror_call_method";
 
-  static Type _FunctionTypeMirror_return_type(functionReflectee, instantiator)
+  static Type _FunctionTypeMirror_return_type(functionReflectee)
       native "FunctionTypeMirror_return_type";
 
   List<ParameterMirror> _FunctionTypeMirror_parameters(functionReflectee)