Delay DownloadManager creation by adding a callback queue to DownloadService

chrome/browser/download/download_service.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_DOWNLOAD_DOWNLOAD_SERVICE_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_SERVICE_H_
 #pragma once
 
+#include <vector>
+
 #include "base/basictypes.h"
+#include "base/callback_forward.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 
 class ChromeDownloadManagerDelegate;
 class DownloadManager;
 class Profile;
 class DownloadIdFactory;
 
 // Owning class for DownloadManager (content) and
 // ChromeDownloadManagerDelegate (chrome)
 class DownloadService : public ProfileKeyedService {
  public:
   explicit DownloadService(Profile* profile);
   virtual ~DownloadService();
 
   DownloadIdFactory* GetDownloadIdFactory() const;
 
+  // Register a callback to be called whenever the DownloadManager is created.
+  typedef base::Callback<void(DownloadManager*)> OnManagerCreatedCallback;
+  void OnManagerCreated(const OnManagerCreatedCallback& cb);
+
   // Get the download manager.  Creates the download manager if
   // it does not already exist.
   DownloadManager* GetDownloadManager();
 
   // Has a download manager been created?  (By calling above function.)
   bool HasCreatedDownloadManager();
 
   // Number of downloads associated with this instance of the service.
   int DownloadCount() const;
 
@@ skipping 19 matching lines @@
   // Both of these objects are owned by this class.
   // DownloadManager is RefCountedThreadSafe because of references
   // from DownloadFile objects on the FILE thread, and may need to be
   // kept alive until those objects are deleted.
   // ChromeDownloadManagerDelegate may be the target of callbacks from
   // the history service/DB thread and must be kept alive for those
   // callbacks.
   scoped_refptr<DownloadManager> manager_;
   scoped_refptr<ChromeDownloadManagerDelegate> manager_delegate_;
 
+  std::vector<OnManagerCreatedCallback> on_manager_created_callbacks_;
+
   DISALLOW_COPY_AND_ASSIGN(DownloadService);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_SERVICE_H_