Fix SharedWorker leak when script load has failed.

When SharedWorker script load has failed and the |WebSharedWorkerImpl|
was explicit told to terminate, the |WebSharedWorkerImpl| instance
was never deleted.

This CL fixes the issue by invoking "delete this" when a worker thread
instance does not exist in |stopWorkerThread()|.

TEST=fast/workers/worker-crash-with-invalid-location.html doesn't leak when --enable-leak-detection
BUG=364390

Review URL: https://codereview.chromium.org/424653002

git-svn-id: svn://svn.chromium.org/blink/trunk@179011 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/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)