Make TypedefMirror a direct descendant of TypeMirror.

tests/lib/mirrors/function_type_mirror_test.dart

Index: tests/lib/mirrors/function_type_mirror_test.dart
diff --git a/tests/lib/mirrors/function_type_mirror_test.dart b/tests/lib/mirrors/function_type_mirror_test.dart
index f712d737e589ad46b7eeb9ca88d6d22d2c7f08af..3b547e3a30e0a2c7aad8116051107a0733b0f660 100644
--- a/tests/lib/mirrors/function_type_mirror_test.dart
+++ b/tests/lib/mirrors/function_type_mirror_test.dart
@@ -11,7 +11,7 @@ typedef void FooFunction(int a, double b);
 bar(int a) {}
 
 main() {
-  TypedefMirror tm = reflectClass(FooFunction);
+  TypedefMirror tm = reflectType(FooFunction);
   FunctionTypeMirror ftm = tm.referent;
   Expect.equals(const Symbol('void'), ftm.returnType.simpleName);
   Expect.equals(#int, ftm.parameters[0].type.simpleName);