Use the ThreadPool for all isolates and native ports. Previously,

runtime/vm/thread_pool.cc

 // 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.
 
 #include "vm/thread_pool.h"
 
 namespace dart {
 
 DEFINE_FLAG(int, worker_timeout_millis, 5000,
             "Free workers when they have been idle for this amount of time.");
@@ skipping 210 matching lines @@
 
 
 void ThreadPool::Worker::StartThread() {
 #if defined(DEBUG)
   // Must call SetTask before StartThread.
   { // NOLINT
     MonitorLocker ml(&monitor_);
     ASSERT(task_ != NULL);
   }
 #endif
-  Thread::Start(&Worker::Main, reinterpret_cast<uword>(this));
+  int result = Thread::Start(&Worker::Main, reinterpret_cast<uword>(this));
+  if (result != 0) {
+    FATAL1("Could not start worker thread: result = %d.", result);
+  }
 }
 
 
 void ThreadPool::Worker::SetTask(Task* task) {
   MonitorLocker ml(&monitor_);
   ASSERT(task_ == NULL);
   task_ = task;
   ml.Notify();
 }
 
@@ skipping 77 matching lines @@
   // The exit monitor is only used during testing.
   if (ThreadPool::exit_monitor_) {
     MonitorLocker ml(ThreadPool::exit_monitor_);
     (*ThreadPool::exit_count_)++;
     ml.Notify();
   }
   delete worker;
 }
 
 }  // namespace dart