Fixes crashes in VM isolate shutdown.

runtime/vm/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_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 514 matching lines @@
     return unhandled_exception_class_;
   }
   static RawClass* unwind_error_class() { return unwind_error_class_; }
   static RawClass* icdata_class() { return icdata_class_; }
   static RawClass* megamorphic_cache_class() {
     return megamorphic_cache_class_;
   }
   static RawClass* subtypetestcache_class() { return subtypetestcache_class_; }
 
   // Initialize the VM isolate.
+  static void InitNull(Isolate* isolate);
   static void InitOnce(Isolate* isolate);
   static void FinalizeVMIsolate(Isolate* isolate);
 
   // Initialize a new isolate either from source or from a snapshot.
   static RawError* Init(Isolate* isolate);
 
   static void MakeUnusedSpaceTraversable(const Object& obj,
                                          intptr_t original_size,
                                          intptr_t used_size);
 
@@ skipping 7309 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_