Make TypedefMirror a direct descendant of TypeMirror.

tests/lib/mirrors/typevariable_mirror_metadata_test.dart

Index: tests/lib/mirrors/typevariable_mirror_metadata_test.dart
diff --git a/tests/lib/mirrors/typevariable_mirror_metadata_test.dart b/tests/lib/mirrors/typevariable_mirror_metadata_test.dart
index aa59870a9ba375c9cff5dfc880ef086b712e5e87..8f9f792821d712017f1efd20a1b537ae885ef5b6 100644
--- a/tests/lib/mirrors/typevariable_mirror_metadata_test.dart
+++ b/tests/lib/mirrors/typevariable_mirror_metadata_test.dart
@@ -42,7 +42,9 @@ main() {
   // Check for conflicts.
   checkMetadata(cm.members[#T], [m1, m2]);
 
-  TypedefMirror tm = reflectClass(Predicate);
-  FunctionTypeMirror ftm = tm.referent;
-  checkMetadata(ftm.typeVariables[0], [m1, m2]);
+  // Partial coverage.
+  return; /// 01: ok
+
+  TypedefMirror tm = reflectType(Predicate);
+  checkMetadata(tm.typeVariables[0], [m1, m2]);
 }