Move Null class out of the VM isolate.

runtime/vm/object_store.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_OBJECT_STORE_H_
 #define VM_OBJECT_STORE_H_
 
 #include "vm/object.h"
 
 namespace dart {
@@ skipping 32 matching lines @@
   void set_object_class(const Class& value) { object_class_ = value.raw(); }
   static intptr_t object_class_offset() {
     return OFFSET_OF(ObjectStore, object_class_);
   }
 
   RawType* object_type() const { return object_type_; }
   void set_object_type(const Type& value) {
     object_type_ = value.raw();
   }
 
+  RawClass* null_class() const {
+    ASSERT(null_class_ != Object::null());
+    return null_class_;
+  }
+  void set_null_class(const Class& value) { null_class_ = value.raw(); }
+
   RawType* null_type() const { return null_type_; }
   void set_null_type(const Type& value) {
     null_type_ = value.raw();
   }
 
   RawType* dynamic_type() const { return dynamic_type_; }
   void set_dynamic_type(const Type& value) {
     dynamic_type_ = value.raw();
   }
 
@@ skipping 357 matching lines @@
   bool PreallocateObjects();
 
   static void Init(Isolate* isolate);
 
  private:
   ObjectStore();
 
   RawObject** from() { return reinterpret_cast<RawObject**>(&object_class_); }
   RawClass* object_class_;
   RawType* object_type_;
+  RawClass* null_class_;
   RawType* null_type_;
   RawType* dynamic_type_;
   RawType* void_type_;
   RawType* function_type_;
   RawClass* type_class_;
   RawClass* type_parameter_class_;
   RawClass* bounded_type_class_;
   RawClass* mixin_app_type_class_;
   RawType* number_type_;
   RawType* int_type_;
@@ skipping 57 matching lines @@
   RawObject** to() { return reinterpret_cast<RawObject**>(&keyword_symbols_); }
 
   friend class SnapshotReader;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectStore);
 };
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_STORE_H_