Make ResourceHandler::OnWillRead able to complete asynchronously.

content/browser/loader/mojo_async_resource_handler.h

 // Copyright 2016 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_LOADER_MOJO_ASYNC_RESOURCE_HANDLER_H_
 #define CONTENT_BROWSER_LOADER_MOJO_ASYNC_RESOURCE_HANDLER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 51 matching lines @@
   // ResourceHandler implementation:
   void OnRequestRedirected(
       const net::RedirectInfo& redirect_info,
       ResourceResponse* response,
       std::unique_ptr<ResourceController> controller) override;
   void OnResponseStarted(
       ResourceResponse* response,
       std::unique_ptr<ResourceController> controller) override;
   void OnWillStart(const GURL& url,
                    std::unique_ptr<ResourceController> controller) override;
-  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;
   void OnDataDownloaded(int bytes_downloaded) override;
 
   // mojom::URLLoader implementation:
   void FollowRedirect() override;
   void SetPriority(net::RequestPriority priority,
@@ skipping 63 matching lines @@
 
   std::unique_ptr<UploadProgressTracker> upload_progress_tracker_;
 
   base::WeakPtrFactory<MojoAsyncResourceHandler> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(MojoAsyncResourceHandler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_MOJO_ASYNC_RESOURCE_HANDLER_H_