Make ResourceHandler::OnWillRead able to complete asynchronously.

content/browser/loader/detachable_resource_handler.h

 // Copyright 2013 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_DETACHABLE_RESOURCE_HANDLER_H_
 #define CONTENT_BROWSER_LOADER_DETACHABLE_RESOURCE_HANDLER_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "content/browser/loader/resource_controller.h"
 #include "content/browser/loader/resource_handler.h"
+#include "content/common/content_export.h"
 
 namespace net {
 class IOBuffer;
 class URLRequest;
 }  // namespace net
 
 namespace content {
 
 class ResourceController;
 
 // A ResourceHandler which delegates all calls to the next handler, unless
 // detached. Once detached, it drives the request to completion itself. This is
 // used for requests which outlive the owning renderer, such as <link
 // rel=prefetch> and <a ping>. Requests do not start out detached so, e.g.,
 // prefetches appear in DevTools and get placed in the renderer's local
 // cache. If the request does not complete after a timeout on detach, it is
 // cancelled.
 //
 // Note that, once detached, the request continues without the original next
 // handler, so any policy decisions in that handler are skipped.
-class DetachableResourceHandler : public ResourceHandler {
+class CONTENT_EXPORT DetachableResourceHandler : public ResourceHandler {
  public:
   DetachableResourceHandler(net::URLRequest* request,
                             base::TimeDelta cancel_delay,
                             std::unique_ptr<ResourceHandler> next_handler);
   ~DetachableResourceHandler() override;
 
   void SetDelegate(Delegate* delegate) override;
 
   bool is_detached() const { return next_handler_ == NULL; }
   void Detach();
 
   void set_cancel_delay(base::TimeDelta cancel_delay) {
     cancel_delay_ = cancel_delay;
   }
 
   // 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;
 
  private:
   class Controller;
 
+  void ResumeInternal();
   void OnTimedOut();
 
   std::unique_ptr<ResourceHandler> next_handler_;
   scoped_refptr<net::IOBuffer> read_buffer_;
 
   std::unique_ptr<base::OneShotTimer> detached_timer_;
   base::TimeDelta cancel_delay_;
 
+  // Only non-NULL between a call to |next_handler_|'s OnWillRead and it
+  // resuming the request.  Needed so that if detached during that time, can
+  // complete the call.
+  scoped_refptr<net::IOBuffer>* parent_read_buffer_;
+  int* parent_read_buffer_size_;
+
   bool is_finished_;
 
   DISALLOW_COPY_AND_ASSIGN(DetachableResourceHandler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_DETACHABLE_RESOURCE_HANDLER_H_