Fix SharedWorker leak when script load has failed.

Source/web/WebSharedWorkerImpl.cpp

Index: Source/web/WebSharedWorkerImpl.cpp
diff --git a/Source/web/WebSharedWorkerImpl.cpp b/Source/web/WebSharedWorkerImpl.cpp
index 1d7d6881361626e888c845e4315715faa8fb596a..af0cc99ccfb7bdb6e037df616f553c8c30e70963 100644
--- a/Source/web/WebSharedWorkerImpl.cpp
+++ b/Source/web/WebSharedWorkerImpl.cpp
@@ -178,12 +178,23 @@ void WebSharedWorkerImpl::stopWorkerThread()
     if (m_askedToTerminate)
         return;
     m_askedToTerminate = true;
+
+    bool hasPendingActivity = false;
     if (m_mainScriptLoader) {
         m_mainScriptLoader->cancel();
         m_mainScriptLoader.clear();
+        hasPendingActivity = true;
     }
-    if (m_workerThread)
+    if (m_workerThread) {
         m_workerThread->stop();
+        hasPendingActivity = true;
+    }
+
+    if (!hasPendingActivity) {
+        // If there are no active WorkerThread, |workerGlobalScopeClosed()|
+        // callback to delete this is never called, so we should clean up here.
+        delete this;
+    }
 }
 
 void WebSharedWorkerImpl::initializeLoader(const WebURL& url)