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

chrome/renderer/extensions/extension_dispatcher.cc

 // 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.
 
 #include "chrome/renderer/extensions/extension_dispatcher.h"
 
 #include "base/command_line.h"
 #include "chrome/common/child_process_logging.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/extensions/extension.h"
@@ skipping 136 matching lines @@
   v8_context_set_.DispatchChromeHiddenMethod(
       extension_id, function_name, args, NULL, event_url);
 
   // Reset the idle handler each time there's any activity like event or message
   // dispatch, for which Invoke is the chokepoint.
   if (is_extension_process_) {
     RenderThread::Get()->ScheduleIdleHandler(
         kInitialExtensionIdleHandlerDelayS);
   }
 
-  // Tell the browser process that we're idle.
+  // Tell the browser process that the event is dispatched and we're idle.
   if (CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kEnableLazyBackgroundPages) &&
-      function_name == "Event.dispatchJSON")  // may always be true
+      function_name == "Event.dispatchJSON") { // may always be true
+    RenderThread::Get()->Send(
+        new ExtensionHostMsg_ExtensionEventAck(extension_id));
+    CheckIdleStatus(extension_id);
+  }
+}
+
+void ExtensionDispatcher::CheckIdleStatus(const std::string& extension_id) {
+  if (!ExtensionProcessBindings::HasPendingRequests(extension_id))
     RenderThread::Get()->Send(new ExtensionHostMsg_ExtensionIdle(extension_id));
 }
 
 void ExtensionDispatcher::OnDeliverMessage(int target_port_id,
                                            const std::string& message) {
   RendererExtensionBindings::DeliverMessage(
       v8_context_set_.GetAll(),
       target_port_id,
       message,
       NULL);  // All render views.
@@ skipping 228 matching lines @@
 
   RenderThread::Get()->RegisterExtension(extension);
 }
 
 void ExtensionDispatcher::OnUsingWebRequestAPI(
     bool adblock, bool adblock_plus, bool other) {
   webrequest_adblock_ = adblock;
   webrequest_adblock_plus_ = adblock_plus;
   webrequest_other_ = other;
 }