Make ResourceHandler::OnWillRead able to complete asynchronously.

content/browser/download/download_resource_handler.cc

 // 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.
 
 #include "content/browser/download/download_resource_handler.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
@@ skipping 153 matching lines @@
 }
 
 void DownloadResourceHandler::OnWillStart(
     const GURL& url,
     std::unique_ptr<ResourceController> controller) {
   controller->Resume();
 }
 
 // Create a new buffer, which will be handed to the download thread for file
 // writing and deletion.
-bool DownloadResourceHandler::OnWillRead(scoped_refptr<net::IOBuffer>* buf,
-                                         int* buf_size) {
-  return core_.OnWillRead(buf, buf_size);
+void DownloadResourceHandler::OnWillRead(
+    scoped_refptr<net::IOBuffer>* buf,
+    int* buf_size,
+    std::unique_ptr<ResourceController> controller) {
+  if (!core_.OnWillRead(buf, buf_size)) {
+    controller->Cancel();
+    return;
+  }
+
+  controller->Resume();
 }
 
 // Pass the buffer to the download file writer.
 void DownloadResourceHandler::OnReadCompleted(
     int bytes_read,
     std::unique_ptr<ResourceController> controller) {
   DCHECK(!has_controller());
 
   bool defer = false;
   if (!core_.OnReadCompleted(bytes_read, &defer)) {
@@ skipping 88 matching lines @@
                             " }",
                             request() ?
                                 request()->url().spec().c_str() :
                                 "<NULL request>",
                             info->GetChildID(),
                             info->GetRequestID(),
                             info->GetRouteID());
 }
 
 }  // namespace content