Enables clean VM shutdown.

runtime/vm/dart.cc

Index: runtime/vm/dart.cc
diff --git a/runtime/vm/dart.cc b/runtime/vm/dart.cc
index 4fd93cb190ae0d0ee5759ad7fbce3e6a8a8c1890..d4a984a1bdec9b7606c2d4d9646e4c2ca5a2c4d8 100644
--- a/runtime/vm/dart.cc
+++ b/runtime/vm/dart.cc
@@ -114,8 +114,6 @@ const char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
   ASSERT(predefined_handles_ == NULL);
   predefined_handles_ = new ReadOnlyHandles();
   // Create the VM isolate and finish the VM initialization.
-  ASSERT(thread_pool_ == NULL);
-  thread_pool_ = new ThreadPool();
   {
     ASSERT(vm_isolate_ == NULL);
     ASSERT(Flags::Initialized());
@@ -198,34 +196,25 @@ const char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
 
 
 const char* Dart::Cleanup() {
-  // Shutdown the service isolate before shutting down the thread pool.
-  ServiceIsolate::Shutdown();
-#if 0
-  // Ideally we should shutdown the VM isolate here, but the thread pool
-  // shutdown does not seem to ensure that all the threads have stopped
-  // execution before it terminates, this results in racing isolates.
+  ASSERT(Isolate::Current() == NULL);
   if (vm_isolate_ == NULL) {
     return "VM already terminated.";
   }
 
-  ASSERT(Isolate::Current() == NULL);
+  // Shutdown the service isolate before shutting down the thread pool.
+  ServiceIsolate::Shutdown();
 
-  delete thread_pool_;
-  thread_pool_ = NULL;
+  // Shutdown the thread pool. On return, all thread pool threads have exited.
+  ThreadPool::Shutdown();
 
   // Set the VM isolate as current isolate.
   Thread::EnsureInit();
   Thread::EnterIsolate(vm_isolate_);
 
-  // There is a planned and known asymmetry here: We exit one scope for the VM
-  // isolate to account for the scope that was entered in Dart_InitOnce.
-  Dart_ExitScope();
-
   ShutdownIsolate();
   vm_isolate_ = NULL;
 
   TargetCPUFeatures::Cleanup();
-#endif
 
   Profiler::Shutdown();
   CodeObservers::DeleteAll();