LifecycleObserver::contextDestroyed should be explicitly dispatched promptly when a context is dest…

Source/platform/LifecycleContext.h

Index: Source/platform/LifecycleContext.h
diff --git a/Source/platform/LifecycleContext.h b/Source/platform/LifecycleContext.h
index d2eee95e45287eb6a63c2a09c35b9b384d67f8ea..2ffe89fd28fa8b0863a9f33e567bd790e7ff3ef7 100644
--- a/Source/platform/LifecycleContext.h
+++ b/Source/platform/LifecycleContext.h
@@ -44,8 +44,16 @@ public:
     typedef LifecycleNotifier<T> Notifier;
     typedef LifecycleObserver<T> Observer;
 
-    LifecycleContext() { }
-    virtual ~LifecycleContext() { }
+    LifecycleContext()
+#if ENABLE(ASSERT)
+        : m_contextDestroyed(false)
+#endif
+    {
+    }
+    virtual ~LifecycleContext()
+    {
+        ASSERT(m_contextDestroyed);
+    }
 
     virtual bool isContextThread() const { return true; }
 
@@ -59,11 +67,21 @@ public:
 
 protected:
     Notifier& lifecycleNotifier();
+    void contextDestroyed()
+    {
+#if ENABLE(ASSERT)
+        ASSERT(!m_contextDestroyed);
+        m_contextDestroyed = true;
+#endif
+        if (m_lifecycleNotifier)
+            m_lifecycleNotifier->contextDestroyed();
+    }
 
 private:
     PassOwnPtr<Notifier> createLifecycleNotifier();
 
     OwnPtr<Notifier> m_lifecycleNotifier;
+    bool m_contextDestroyed;
 };
 
 template<typename T>