Do not reload isolates if we are in the process of shutting down the VM

runtime/vm/isolate.h

 // Copyright (c) 2013, 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_ISOLATE_H_
 #define VM_ISOLATE_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/atomic.h"
@@ skipping 613 matching lines @@
   bool asserts() const { return asserts_; }
   bool error_on_bad_type() const { return error_on_bad_type_; }
   bool error_on_bad_override() const { return error_on_bad_override_; }
 #endif  // defined(PRODUCT)
 
   static void KillAllIsolates(LibMsgId msg_id);
   static void KillIfExists(Isolate* isolate, LibMsgId msg_id);
 
   static void DisableIsolateCreation();
   static void EnableIsolateCreation();
+  static bool IsolateCreationEnabled();
 
   void StopBackgroundCompiler();
 
   intptr_t reload_every_n_stack_overflow_checks() const {
     return reload_every_n_stack_overflow_checks_;
   }
 
   void MaybeIncreaseReloadEveryNStackOverflowChecks();
 
  private:
@@ skipping 345 matching lines @@
   intptr_t* spawn_count_;
 
   Dart_IsolateFlags isolate_flags_;
   bool paused_;
   bool errors_are_fatal_;
 };
 
 }  // namespace dart
 
 #endif  // VM_ISOLATE_H_