Factor out dependncy on download throttling from core download code.

content/browser/renderer_host/resource_dispatcher_host.h

Index: content/browser/renderer_host/resource_dispatcher_host.h
===================================================================
--- content/browser/renderer_host/resource_dispatcher_host.h	(revision 96872)
+++ content/browser/renderer_host/resource_dispatcher_host.h	(working copy)
@@ -31,7 +31,6 @@
 
 class CrossSiteResourceHandler;
 class DownloadFileManager;
-class DownloadRequestLimiter;
 class LoginHandler;
 class NotificationDetails;
 class PluginService;
@@ -147,10 +146,6 @@
     return download_file_manager_;
   }
 
-  DownloadRequestLimiter* download_request_limiter() const {
-    return download_request_limiter_.get();
-  }
-
   SaveFileManager* save_file_manager() const {
     return save_file_manager_;
   }
@@ -463,9 +458,6 @@
   // We own the download file writing thread and manager
   scoped_refptr<DownloadFileManager> download_file_manager_;
 
-  // Determines whether a download is allowed.
-  scoped_refptr<DownloadRequestLimiter> download_request_limiter_;
-
   // We own the save file manager.
   scoped_refptr<SaveFileManager> save_file_manager_;