Worker: Introduce an observation mechanism for WorkerThread termination

third_party/WebKit/Source/core/workers/WorkerThread.cpp

Index: third_party/WebKit/Source/core/workers/WorkerThread.cpp
diff --git a/third_party/WebKit/Source/core/workers/WorkerThread.cpp b/third_party/WebKit/Source/core/workers/WorkerThread.cpp
index d470e8e2ae8eb902d49d06c57b54888fed418dac..37c77d3b6f633184bff0e95685da6bb0d76c0519 100644
--- a/third_party/WebKit/Source/core/workers/WorkerThread.cpp
+++ b/third_party/WebKit/Source/core/workers/WorkerThread.cpp
@@ -154,6 +154,24 @@ static HashSet<WorkerThread*>& workerThreads()
     return threads;
 }
 
+WorkerThreadContext::WorkerThreadContext()
+{
+    DCHECK(isMainThread());
+}
+
+WorkerThreadContext::~WorkerThreadContext()
+{
+    DCHECK(isMainThread());
+}
+
+void WorkerThreadContext::notifyContextDestroyed()
+{
+    DCHECK(isMainThread());
+    DCHECK(!m_wasContextDestroyed);
+    m_wasContextDestroyed = true;
+    LifecycleNotifier::notifyContextDestroyed();
+}
+
 WorkerThread::~WorkerThread()
 {
     DCHECK(isMainThread());
@@ -307,7 +325,9 @@ WorkerThread::WorkerThread(PassRefPtr<WorkerLoaderProxy> workerLoaderProxy, Work
     , m_shutdownEvent(adoptPtr(new WaitableEvent(
         WaitableEvent::ResetPolicy::Manual,
         WaitableEvent::InitialState::NonSignaled)))
+    , m_workerThreadContext(new WorkerThreadContext)
 {
+    DCHECK(isMainThread());
     MutexLocker lock(threadSetMutex());
     workerThreads().add(this);
 }
@@ -354,6 +374,8 @@ void WorkerThread::terminateInternal(TerminationMode mode)
     if (m_terminationEvent)
         m_terminationEvent->signal();
 
+    m_workerThreadContext->notifyContextDestroyed();
+
     // If the worker thread was never initialized, don't start another
     // shutdown, but still wait for the thread to signal when shutdown has
     // completed on initializeOnWorkerThread().