- Add a size field to the header.

vm/object.h

 // Copyright (c) 2011, 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_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "vm/assert.h"
 #include "vm/dart.h"
 #include "vm/globals.h"
@@ skipping 134 matching lines @@
     kApiErrorClass,
     kMaxId,
     kInvalidIndex = -1,
   };
 
   virtual ~Object() { }
 
   RawObject* raw() const { return raw_; }
   void operator=(RawObject* value) { SetRaw(value); }
 
-  void set_tags(intptr_t tags) {
+  void set_tags(intptr_t value) {
+    // TODO(asiva): Remove the capability of setting tags in general. The mask
+    // here only allows for canonical and from_snapshot flags to be set.
     ASSERT(!IsNull());
-    raw()->ptr()->tags_ = tags;
+    uword tags = raw()->ptr()->tags_ & ~0x0000000c;
+    raw()->ptr()->tags_ = tags | (value & 0x0000000c);
   }
   void SetCreatedFromSnapshot() const {
     ASSERT(!IsNull());
     raw()->SetCreatedFromSnapshot();
   }
   bool IsCanonical() const {
     ASSERT(!IsNull());
     return raw()->IsCanonical();
   }
   void SetCanonical() const {
@@ skipping 194 matching lines @@
   static RawClass* library_prefix_class_;  // Class of Library prefix vm object.
   static RawClass* code_class_;  // Class of the Code vm object.
   static RawClass* instructions_class_;  // Class of the Instructions vm object.
   static RawClass* pc_descriptors_class_;  // Class of PcDescriptors vm object.
   static RawClass* var_descriptors_class_;  // Class of LocalVarDescriptors.
   static RawClass* exception_handlers_class_;  // Class of ExceptionHandlers.
   static RawClass* context_class_;  // Class of the Context vm object.
   static RawClass* context_scope_class_;  // Class of ContextScope vm object.
   static RawClass* api_error_class_;  // Class of ApiError.
 
+  friend void RawObject::Validate() const;
   friend class Class;
   friend class SnapshotReader;
 
   // Disallow allocation.
   void* operator new(size_t size);
   // Disallow copy constructor.
   DISALLOW_COPY_AND_ASSIGN(Object);
 };
 
 
@@ skipping 2966 matching lines @@
 }
 
 
 void Context::SetAt(intptr_t index, const Instance& value) const {
   StorePointer(InstanceAddr(index), value.raw());
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_