Make ResourceHandler::OnWillRead able to complete asynchronously.

content/browser/download/download_resource_handler.h

 // Copyright (c) 2012 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 CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_RESOURCE_HANDLER_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_RESOURCE_HANDLER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 48 matching lines @@
   void OnResponseStarted(
       ResourceResponse* response,
       std::unique_ptr<ResourceController> controller) override;
 
   // Pass-through implementation.
   void OnWillStart(const GURL& url,
                    std::unique_ptr<ResourceController> controller) override;
 
   // Create a new buffer, which will be handed to the download thread for file
   // writing and deletion.
-  bool OnWillRead(scoped_refptr<net::IOBuffer>* buf,
-                  int* buf_size) override;
+  void OnWillRead(scoped_refptr<net::IOBuffer>* buf,
+                  int* buf_size,
+                  std::unique_ptr<ResourceController> controller) override;
 
   void OnReadCompleted(int bytes_read,
                        std::unique_ptr<ResourceController> controller) override;
 
   void OnResponseCompleted(
       const net::URLRequestStatus& status,
       std::unique_ptr<ResourceController> controller) override;
 
   // N/A to this flavor of DownloadHandler.
   void OnDataDownloaded(int bytes_downloaded) override;
@@ skipping 25 matching lines @@
   std::unique_ptr<DownloadTabInfo> tab_info_;
 
   DownloadRequestCore core_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadResourceHandler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_RESOURCE_HANDLER_H_