Have the Worker destructor handle non-started Workers better.

Source/core/workers/Worker.cpp

Index: Source/core/workers/Worker.cpp
diff --git a/Source/core/workers/Worker.cpp b/Source/core/workers/Worker.cpp
index f6056006676c2247d2535440e36e07b9036a83de..fb5bfc796db25238bf50dd77e5cb12c6e215a701 100644
--- a/Source/core/workers/Worker.cpp
+++ b/Source/core/workers/Worker.cpp
@@ -82,9 +82,10 @@ PassRefPtrWillBeRawPtr<Worker> Worker::create(ExecutionContext* context, const S
 Worker::~Worker()
 {
     ASSERT(isMainThread());
+    if (!m_contextProxy)
+        return;
     ASSERT(executionContext()); // The context is protected by worker context proxy, so it cannot be destroyed while a Worker exists.
-    if (m_contextProxy)
-        m_contextProxy->workerObjectDestroyed();
+    m_contextProxy->workerObjectDestroyed();
 }
 
 const AtomicString& Worker::interfaceName() const
@@ -114,7 +115,7 @@ void Worker::stop()
 
 bool Worker::hasPendingActivity() const
 {
-    return m_contextProxy->hasPendingActivity() || ActiveDOMObject::hasPendingActivity();
+    return (m_contextProxy && m_contextProxy->hasPendingActivity()) || ActiveDOMObject::hasPendingActivity();
 }
 
 void Worker::didReceiveResponse(unsigned long identifier, const ResourceResponse&)