Add a VM defined class MirrorReference as an opaque pointer for Dart code to VM internal objects.

runtime/lib/mirrors.cc

Index: runtime/lib/mirrors.cc
===================================================================
--- runtime/lib/mirrors.cc	(revision 24540)
+++ runtime/lib/mirrors.cc	(working copy)
@@ -125,7 +125,7 @@
 
 static Dart_Handle CreateVMReference(Dart_Handle handle) {
   // Create the VMReference object.
-  Dart_Handle cls_name = NewString("VMReference");
+  Dart_Handle cls_name = NewString("OldVMReference");

[siva, 2013/06/30 01:12:48]

VMReference for the new internal VM class seems very generic why not call it
something mirror or reflection related?

InstanceReflector
ObjectReflector
ObjectMirror

or something like that.

[rmacnak, 2013/07/01 15:50:28]

It is intended to be rather generic. It might hold a Class, Library, Type,
Function or Instance depending on what kind of mirror is using it. Itself it is
not a mirror because it does not respond to any part of the mirror API. Perhaps
MirrorReference or MirrorReflectee?

   Dart_Handle type = Dart_GetType(MirrorLib(), cls_name, 0, NULL);
   if (Dart_IsError(type)) {
     return type;