Make TypedefMirror a direct descendant of TypeMirror.

tests/lib/mirrors/typedef_metadata_test.dart

Index: tests/lib/mirrors/typedef_metadata_test.dart
diff --git a/tests/lib/mirrors/typedef_metadata_test.dart b/tests/lib/mirrors/typedef_metadata_test.dart
index e07339ae459cc299350cee477c32c8f420c9acbe..8a70c7ac192c37a5ac8a99caa03bbbcd2c0c011c 100644
--- a/tests/lib/mirrors/typedef_metadata_test.dart
+++ b/tests/lib/mirrors/typedef_metadata_test.dart
@@ -18,6 +18,6 @@ typedef MA = S with M;
 typedef bool Predicate(Object o);
 
 main() {
-  checkMetadata(reflectClass(MA), [symbol]);
-  checkMetadata(reflectClass(Predicate), [string]);
+  checkMetadata(reflectType(MA), [symbol]);
+  checkMetadata(reflectType(Predicate), [string]);
 }