Treat null like the object it is in the Observatory and Service.

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 359 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 IsNullOrPseudoNull() {
+    return (!IsHeapObject() && (GetClassId() == kNullCid));
+  }

[turnidge, 2014/08/27 16:13:56]

I missed where this is used... can you tell me?

[rmacnak, 2014/08/27 18:09:59]

Was used in guard for values not to insert in the ring. Removed based on
narrowed restriction..

   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 1607 matching lines @@
   COMPILE_ASSERT(kExternalTypedDataInt8ArrayCid ==
                  kTypedDataInt8ArrayViewCid + 15);
   COMPILE_ASSERT(kByteBufferCid == kExternalTypedDataInt8ArrayCid + 14);
   COMPILE_ASSERT(kNullCid == kByteBufferCid + 1);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_