Quick fix for racy shutdown issues in VmStats.

runtime/bin/vmstats_impl.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 BIN_VMSTATS_IMPL_H_
 #define BIN_VMSTATS_IMPL_H_
 
 #include "bin/vmstats.h"
 
 #include <map>
@@ skipping 25 matching lines @@
   char* IsolatesStatus();
 
   typedef std::map<IsolateData*, Dart_Isolate> IsolateTable;
 
   std::string root_directory_;
   IsolateTable isolate_table_;
   bool running_;
   int64_t bind_address_;
 
   static VmStats* instance_;
-  static dart::Monitor instance_monitor_;
+  static dart::Monitor* instance_monitor_;
 
   // Disallow copy constructor.
   DISALLOW_COPY_AND_ASSIGN(VmStats);
 };
 
 
 // Status plug-in and linked-list node.
 class VmStatusPlugin {
  public:
   explicit VmStatusPlugin(Dart_VmStatusCallback callback)
@@ skipping 25 matching lines @@
   // Returns VM status for a specified request. The caller is responsible
   // for releasing the heap memory after use.
   static char* GetVmStatus(const char* request);
 
   static void InitOnce();
 
  private:
   VmStatusService() : registered_plugin_list_(NULL) {}
 
   static VmStatusService* instance_;
-  static dart::Mutex mutex_;
+  static dart::Mutex* mutex_;
 
   VmStatusPlugin* registered_plugin_list_;
 
   DISALLOW_COPY_AND_ASSIGN(VmStatusService);
 };
 
 #endif  // BIN_VMSTATS_IMPL_H_