Remove more feature in product mode

runtime/vm/thread_interrupter.cc

 // 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.
 
 #include "vm/thread_interrupter.h"
 
 #include "vm/flags.h"
 #include "vm/lockers.h"
 #include "vm/os.h"
 #include "vm/simulator.h"
 
 namespace dart {
 
+#ifndef PRODUCT
+
 // Notes:
 //
 // The ThreadInterrupter interrupts all threads actively running isolates once
 // per interrupt period (default is 1 millisecond). While the thread is
 // interrupted, the thread's interrupt callback is invoked. Callbacks cannot
 // rely on being executed on the interrupted thread.
 //
 // There are two mechanisms used to interrupt a thread. The first, used on OSs
 // with pthreads (Android, Linux, and Mac), is thread specific signal delivery.
 // The second, used on Windows, is explicit suspend and resume thread system
@@ skipping 193 matching lines @@
     OS::Print("ThreadInterrupter thread exiting.\n");
   }
   {
     // Signal to main thread we are exiting.
     MonitorLocker shutdown_ml(monitor_);
     thread_running_ = false;
     shutdown_ml.Notify();
   }
 }
 
+#endif  // !PRODUCT
+
 }  // namespace dart