Make TypedefMirror a direct descendant of TypeMirror.

runtime/lib/mirrors.cc

Index: runtime/lib/mirrors.cc
diff --git a/runtime/lib/mirrors.cc b/runtime/lib/mirrors.cc
index 3f70c58d1d951021005c34c6a0349267283d5877..6ebb080bcb4ff79fdfbee744e482402e00a7b3f7 100644
--- a/runtime/lib/mirrors.cc
+++ b/runtime/lib/mirrors.cc
@@ -418,7 +418,10 @@ DEFINE_NATIVE_ENTRY(Mirrors_makeLocalClassMirror, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(Type, type, arguments->NativeArgAt(0));
   const Class& cls = Class::Handle(type.type_class());
   ASSERT(!cls.IsNull());
-  if (cls.IsDynamicClass() || cls.IsVoidClass()) {
+  if (cls.IsDynamicClass() ||
+      cls.IsVoidClass() ||
+      (cls.IsSignatureClass() && !cls.IsCanonicalSignatureClass())) {
+    // dynamic, void or a function typedef.
     const Array& args = Array::Handle(Array::New(1));
     args.SetAt(0, type);
     Exceptions::ThrowByType(Exceptions::kArgument, args);