Fix failing test on windows. I was accessing a stat too early.

runtime/vm/thread_pool_test.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/os.h"
 #include "vm/thread.h"
 #include "vm/thread_pool.h"
 #include "vm/unit_test.h"
 
 namespace dart {
@@ skipping 45 matching lines @@
     MonitorLocker ml(&sync);
     while (!done) {
       ml.Wait();
     }
   }
   EXPECT(done);
 
   // Do a sanity test on the worker stats.
   EXPECT_EQ(1U, thread_pool.workers_started());
   EXPECT_EQ(0U, thread_pool.workers_stopped());
-  EXPECT_EQ(1U, thread_pool.workers_idle());
-  EXPECT_EQ(0U, thread_pool.workers_running());
 }
 
 
 UNIT_TEST_CASE(ThreadPool_RunMany) {
   const int kTaskCount = 100;
   ThreadPool thread_pool;
   Monitor sync[kTaskCount];
   bool done[kTaskCount];
 
   for (int i = 0; i < kTaskCount; i++) {
@@ skipping 133 matching lines @@
     MonitorLocker ml(&sync);
     while (done < kTotalTasks) {
       ml.Wait();
     }
   }
   EXPECT_EQ(kTotalTasks, done);
 }
 
 
 }  // namespace dart