Never return a Dart_Handle on a dart::Class from the embedding API.

runtime/vm/raw_object.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/globals.h"
 #include "vm/token.h"
@@ skipping 329 matching lines @@
   void SetRememberedBit() {
     ASSERT(!IsRemembered());
     uword tags = ptr()->tags_;
     ptr()->tags_ = RememberedBit::update(true, tags);
   }
   void ClearRememberedBit() {
     uword tags = ptr()->tags_;
     ptr()->tags_ = RememberedBit::update(false, tags);
   }
 
+  bool IsRawClass() {

[rmacnak, 2013/09/19 00:46:04]

Will remove before commit, just here to demonstrate.

+    return IsHeapObject() && (GetClassId() == kClassCid);
+  }
+
   bool IsDartInstance() {
     return (!IsHeapObject() || (GetClassId() >= kInstanceCid));
   }
   bool IsFreeListElement() {
     return ((GetClassId() == kFreeListElement));
   }
 
   intptr_t Size() const {
     uword tags = ptr()->tags_;
     intptr_t result = SizeTag::decode(tags);
@@ skipping 1351 matching lines @@
   // Make sure this is updated when new TypedData types are added.
   ASSERT(kTypedDataInt8ArrayViewCid == kTypedDataInt8ArrayCid + 12);
   ASSERT(kExternalTypedDataInt8ArrayCid == kTypedDataInt8ArrayViewCid + 13);
   ASSERT(kNullCid == kExternalTypedDataInt8ArrayCid + 12);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_