ServiceWorker: Fix data race in shutdown sequence

Source/core/workers/WorkerThread.cpp

Index: Source/core/workers/WorkerThread.cpp
diff --git a/Source/core/workers/WorkerThread.cpp b/Source/core/workers/WorkerThread.cpp
index 4afc1f86c0dd84d85880c9f0ca1d31ee3f73c104..f67780dcb86c32f9727af46c2364d148e18eaa8c 100644
--- a/Source/core/workers/WorkerThread.cpp
+++ b/Source/core/workers/WorkerThread.cpp
@@ -415,6 +415,12 @@ void WorkerThread::stopInShutdownSequence()
     stopInternal();
 }
 
+void WorkerThread::terminateAndWait()
+{
+    stop();

[horo, 2014/10/30 08:14:47]

I think we don't need to call stop() from the destructor of
WebEmbeddedWorkerImpl.

WebEmbeddedWorkerImpl is deleted after
ServiceWorkerGlobalScopeProxy::workerThreadTerminated() is called.
So when deleting WebEmbeddedWorkerImpl, m_workerThread->terminated() must be
true.

Adding "ASSERT(m_workerThread->terminated())" in the destructor of
WebEmbeddedWorkerImpl is better.

[Kunihiko Sakamoto, 2014/10/30 08:31:29]

Done.

+    terminationEvent()->wait();
+}
+
 bool WorkerThread::terminated()
 {
     MutexLocker lock(m_threadCreationMutex);