Oilpan: IDBCursor should be detached from IDBRequest when the IDBRequest stops

Source/platform/LifecycleObserver.h

 /*
  * Copyright (C) 2008 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 38 matching lines @@
         , m_observerType(type)
     {
         observeContext(context);
     }
 
     virtual ~LifecycleObserver()
     {
         observeContext(0);
     }
 
+    virtual void contextWillBeDestroyed() { }
     virtual void contextDestroyed() { m_lifecycleContext = 0; }
 
-
     Context* lifecycleContext() const { return m_lifecycleContext; }
     Type observerType() const { return m_observerType; }
 
 protected:
     void observeContext(Context*);
 
     Context* m_lifecycleContext;
     Type m_observerType;
 };
 
@@ skipping 12 matching lines @@
 
     m_lifecycleContext = context;
 
     if (m_lifecycleContext)
         observerContext(m_lifecycleContext, this);
 }
 
 } // namespace WebCore
 
 #endif // LifecycleObserver_h