Make Notification override hasPendingActivity() to prolong its lifetime while async op is running

Source/modules/notifications/Notification.h

Index: Source/modules/notifications/Notification.h
diff --git a/Source/modules/notifications/Notification.h b/Source/modules/notifications/Notification.h
index ef50d83910a20677612ccfdb64cb926ae896e205..31ad6f36d06ebbad7a99b9c42318a39fb42ca587 100644
--- a/Source/modules/notifications/Notification.h
+++ b/Source/modules/notifications/Notification.h
@@ -71,6 +71,11 @@ public:
 
     virtual ~Notification();
 
+    // Calling show() may start asynchronous operation. If this object has
+    // a V8 wrapper, hasPendingActivity() prevents the wrapper from being
+    // collected while m_state is Showing, and so this instance stays alive
+    // until the operation completes. Otherwise, you need to hold a ref on this
+    // instance until the operation completes.
     void show();
 #if ENABLE(LEGACY_NOTIFICATIONS)
     void cancel() { close(); }
@@ -116,6 +121,8 @@ public:
     virtual bool dispatchEvent(PassRefPtr<Event>) OVERRIDE;
 
     // ActiveDOMObject interface
+    // Override to prevent this from being collected when in Showing state.
+    virtual bool hasPendingActivity() const OVERRIDE;
     virtual void stop() OVERRIDE;
 
     static const String& permission(ExecutionContext*);
@@ -128,8 +135,6 @@ private:
 #endif
     Notification(ExecutionContext*, const String& title);
 
-    void finalize();
-
     void setLang(const String& lang) { m_lang = lang; }
     void setBody(const String& body) { m_body = body; }
     void setIcon(const KURL& url) { m_icon = url; }