Protecting against other possible uses of invalid V8 execution context.

Source/modules/indexeddb/IDBTransaction.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 323 matching lines @@
 }
 
 ExecutionContext* IDBTransaction::executionContext() const
 {
     return ActiveDOMObject::executionContext();
 }
 
 bool IDBTransaction::dispatchEvent(PassRefPtr<Event> event)
 {
     IDB_TRACE("IDBTransaction::dispatchEvent");
+    if (m_contextStopped || !executionContext()) {
+        m_state = Finished;
+        return false;
+    }
     ASSERT(m_state != Finished);
     ASSERT(m_hasPendingActivity);
     ASSERT(executionContext());
     ASSERT(event->target() == this);
     m_state = Finished;
 
     // Break reference cycles.
     for (IDBObjectStoreMap::iterator it = m_objectStoreMap.begin(); it != m_objectStoreMap.end(); ++it)
         it->value->transactionFinished();
     m_objectStoreMap.clear();
@@ skipping 38 matching lines @@
     event->setTarget(this);
     eventQueue->enqueueEvent(event);
 }
 
 blink::WebIDBDatabase* IDBTransaction::backendDB() const
 {
     return m_database->backend();
 }
 
 } // namespace WebCore