Implement safepointing of threads

runtime/vm/lockers.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_LOCKERS_H_
 #define VM_LOCKERS_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/globals.h"
@@ skipping 32 matching lines @@
 
   virtual ~MonitorLocker() {
     monitor_->Exit();
     // TODO(iposva): Consider decrementing the no GC scope here.
   }
 
   Monitor::WaitResult Wait(int64_t millis = Monitor::kNoTimeout) {
     return monitor_->Wait(millis);
   }
 
+  Monitor::WaitResult WaitWithSafepointCheck(
+      Thread* thread, int64_t millis = Monitor::kNoTimeout);
+
   Monitor::WaitResult WaitMicros(int64_t micros = Monitor::kNoTimeout) {
     return monitor_->WaitMicros(micros);
   }
 
   void Notify() {
     monitor_->Notify();
   }
 
   void NotifyAll() {
     monitor_->NotifyAll();
   }
 
  private:
   Monitor* const monitor_;
 
   DISALLOW_COPY_AND_ASSIGN(MonitorLocker);
 };
 
 }  // namespace dart
 
 
 #endif  // VM_LOCKERS_H_