Fixes shutdown crashes.

runtime/vm/virtual_memory.cc

 // 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.
 
 #include "vm/virtual_memory.h"
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 
 namespace dart {
@@ skipping 15 matching lines @@
   }
   region_.Subregion(region_, 0, new_size);
 }
 
 
 VirtualMemory* VirtualMemory::ForInstructionsSnapshot(void* pointer,
                                                       uword size) {
   // Memory for precompilated instructions was allocated by the embedder, so
   // create a VirtualMemory without allocating.
   MemoryRegion region(pointer, size);
-  return new VirtualMemory(region);
+  VirtualMemory* memory = new VirtualMemory(region);
+  memory->embedder_allocated_ = true;
+  return memory;
 }
 
 }  // namespace dart