Refactor Thread lifecycle interface, add Thread::Enter/ExitIsolate.

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"
 
 #include "vm/flags.h"
 #include "vm/lockers.h"
 
 namespace dart {
@@ skipping 256 matching lines @@
 void ThreadPool::Worker::Loop() {
   MonitorLocker ml(&monitor_);
   int64_t idle_start;
   while (true) {
     ASSERT(task_ != NULL);
     Task* task = task_;
     task_ = NULL;
 
     // Release monitor while handling the task.
     monitor_.Exit();
+    Thread::EnsureInit();
     task->Run();
+    ASSERT(Isolate::Current() == NULL);
+    // Prevent unintended sharing of state between tasks.
+    Thread::CleanUp();
     delete task;
     monitor_.Enter();
 
     ASSERT(task_ == NULL);
     if (IsDone()) {
       return;
     }
     ASSERT(pool_ != NULL);
     pool_->SetIdle(this);
     idle_start = OS::GetCurrentTimeMillis();
@@ skipping 37 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