Delay DownloadManager creation by adding a callback queue to DownloadService

chrome/browser/download/download_service.h

Index: chrome/browser/download/download_service.h
diff --git a/chrome/browser/download/download_service.h b/chrome/browser/download/download_service.h
index 2317de1a92bf7b374874c72e6d641b02575f3455..41f659b8c09841780477b5270e80efacf1b8f3c0 100644
--- a/chrome/browser/download/download_service.h
+++ b/chrome/browser/download/download_service.h
@@ -6,7 +6,10 @@
 #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"
@@ -25,6 +28,10 @@ class DownloadService : public ProfileKeyedService {
 
   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();
@@ -64,6 +71,8 @@ class DownloadService : public ProfileKeyedService {
   scoped_refptr<DownloadManager> manager_;
   scoped_refptr<ChromeDownloadManagerDelegate> manager_delegate_;
 
+  std::vector<OnManagerCreatedCallback> on_manager_created_callbacks_;
+
   DISALLOW_COPY_AND_ASSIGN(DownloadService);
 };