Fix crash walking call stack on Linux.

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/simulator.h"
 #include "vm/thread_interrupter.h"
 
 namespace dart {
 
 // Notes:
@@ skipping 334 matching lines @@
   // Pop.
   threads_size_--;
   return state;
 }
 
 
 void ThreadInterruptNoOp(const InterruptedThreadState& state, void* data) {
   // NoOp.
 }
 
+
 void ThreadInterrupter::ThreadMain(uword parameters) {
   ASSERT(initialized_);
   InstallSignalHandler();
   if (FLAG_trace_thread_interrupter) {
     OS::Print("ThreadInterrupter thread running.\n");
   }
   {
     // Signal to main thread we are ready.
     MonitorLocker startup_ml(monitor_);
     thread_running_ = true;
@@ skipping 13 matching lines @@
   }
   {
     // Signal to main thread we are exiting.
     MonitorLocker shutdown_ml(monitor_);
     thread_running_ = false;
     shutdown_ml.Notify();
   }
 }
 
 }  // namespace dart