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

chrome/renderer/extensions/extension_process_bindings.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.
 
 // Exposes extension APIs into the extension process.
 
 #ifndef CHROME_RENDERER_EXTENSIONS_EXTENSION_PROCESS_BINDINGS_H_
 #define CHROME_RENDERER_EXTENSIONS_EXTENSION_PROCESS_BINDINGS_H_
 #pragma once
 
 #include <string>
 
 class ExtensionDispatcher;
 class ChromeV8ContextSet;
 class GURL;
 class URLPattern;
 
 namespace WebKit {
 class WebView;
 }
 
 namespace v8 {
 class Extension;
 }
 
 class ExtensionProcessBindings {
  public:
   static v8::Extension* Get(ExtensionDispatcher* extension_dispatcher);
 
-  // Handles a response to an API request.
+  // Handles a response to an API request.  Sets |extension_id|.
   static void HandleResponse(const ChromeV8ContextSet& contexts,
                              int request_id,
                              bool success,
                              const std::string& response,
-                             const std::string& error);
+                             const std::string& error,
+                             std::string* extension_id);
+
+  static bool HasPendingRequests(const std::string& extension_id);
 };
 
 #endif  // CHROME_RENDERER_EXTENSIONS_EXTENSION_PROCESS_BINDINGS_H_