Don't close background pages if there is a pending response (callback).

chrome/browser/extensions/extension_event_router.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_EVENT_ROUTER_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_EVENT_ROUTER_H_
 #pragma once
 
 #include <map>
 #include <set>
@@ skipping 70 matching lines @@
   // If |cross_incognito_profile| is non-NULL and different from
   // restrict_to_profile, send the event with cross_incognito_args to the
   // extensions in that profile that can't cross incognito.
   void DispatchEventsToRenderersAcrossIncognito(
       const std::string& event_name,
       const std::string& event_args,
       Profile* restrict_to_profile,
       const std::string& cross_incognito_args,
       const GURL& event_url);
 
+  // Record the Event Ack from the renderer. (One less event in-flight.)
+  void OnExtensionEventAck(const std::string& extension_id);
+
+  // Check if there are any Extension Events that have not yet been acked by
+  // the renderer.
+  bool HasInFlightEvents(const std::string& extension_id);
+
  protected:
   // The details of an event to be dispatched.
   struct ExtensionEvent;
 
   // Shared by DispatchEvent*. If |extension_id| is empty, the event is
   // broadcast.
   // An event that just came off the pending list may not be delayed again.
   void DispatchEventImpl(const linked_ptr<ExtensionEvent>& event,
                          bool was_pending);
 
@@ skipping 24 matching lines @@
   typedef std::map<std::string, std::set<EventListener> > ListenerMap;
   ListenerMap listeners_;
 
   // A map between an extension id and the queue of events pending
   // the load of it's background page.
   typedef std::vector<linked_ptr<ExtensionEvent> > PendingEventsList;
   typedef std::map<std::string,
                    linked_ptr<PendingEventsList> > PendingEventsPerExtMap;
   PendingEventsPerExtMap pending_events_;
 
+  // Track of the number of dispatched events that have not yet sent an
+  // ACK from the renderer.
+  void IncrementInFlightEvents(const std::string& extension_id);
+  std::map<std::string, int> in_flight_events_;
+
   DISALLOW_COPY_AND_ASSIGN(ExtensionEventRouter);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_EVENT_ROUTER_H_