content::ResourceDispatcherHostImpl changes for stale-while-revalidate

content/browser/loader/async_revalidation_driver.h

Index: content/browser/loader/async_revalidation_driver.h
diff --git a/content/browser/loader/async_revalidation_driver.h b/content/browser/loader/async_revalidation_driver.h
new file mode 100644
index 0000000000000000000000000000000000000000..5be7af548171c48c9856f015bac2f946b2842d13
--- /dev/null
+++ b/content/browser/loader/async_revalidation_driver.h
@@ -0,0 +1,97 @@
+// Copyright 2015 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_ASYNC_REVALIDATION_DRIVER_H_
+#define CONTENT_BROWSER_LOADER_ASYNC_REVALIDATION_DRIVER_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/timer/timer.h"
+#include "content/common/content_export.h"
+#include "content/public/browser/resource_controller.h"
+#include "content/public/browser/resource_throttle.h"
+#include "net/base/io_buffer.h"
+#include "net/url_request/url_request.h"
+
+namespace net {
+class HttpCache;
+}
+
+namespace content {
+
+// This class is responsible for driving the URLRequest for an async
+// revalidation. It is passed an instance of ResourceThrottle created by
+// content::ResourceScheduler to perform throttling on the request.
+class CONTENT_EXPORT AsyncRevalidationDriver : public net::URLRequest::Delegate,
+                                               public ResourceController {
+ public:
+  // |completion_callback| is guaranteed to be called on completion,
+  // regardless of success or failure.
+  AsyncRevalidationDriver(scoped_ptr<net::URLRequest> request,
+                          scoped_ptr<ResourceThrottle> throttle,
+                          const base::Closure& completion_callback);
+  ~AsyncRevalidationDriver() override;
+
+  void StartRequest();
+  void CancelRequest();

[davidben, 2015/12/07 23:56:03]

What need is there to make CancelRequest() a distinct API from the destructor?
When you can avoid it, just using the destructor makes a lot of questions
simpler as you no longer have distinct states for things.

It's especially confusing because CancelRequest will call completion_callback,
but only if you don't destroy the driver first.

(Same comment from previous iteration. Might have missed it.)

[Adam Rice, 2015/12/08 18:05:35]

Sorry I missed this. I have removed CancelRequest(). Many things are now
simpler.

+
+ private:
+  enum TimeoutType {
+    RESPONSE_TIMEOUT,
+    READ_TIMEOUT
+  };
+
+  // net::URLRequest::Delegate implementation:
+  void OnReceivedRedirect(net::URLRequest* request,
+                          const net::RedirectInfo& redirect_info,
+                          bool* defer) override;
+  void OnAuthRequired(net::URLRequest* request,
+                      net::AuthChallengeInfo* info) override;
+  void OnBeforeNetworkStart(net::URLRequest* request, bool* defer) override;
+  void OnResponseStarted(net::URLRequest* request) override;
+  void OnReadCompleted(net::URLRequest* request, int bytes_read) override;
+
+  // ResourceController implementation:
+  void Resume() override;
+
+  // For simplicity, this class assumes that ResourceScheduler never cancels
+  // requests, and so these three methods are never called.
+  void Cancel() override;
+  void CancelAndIgnore() override;
+  void CancelWithError(int error_code) override;
+
+  // Internal methods.
+  void StartRequestInternal();
+  void CancelRequestInternal(int error);
+  void StartReading(bool is_continuation);
+  void ResumeReading();
+  void ReadMore(int* bytes_read);
+  // Calls |completion_callback_| and clears it.
+  void ResponseCompleted();
+  void OnTimeout(TimeoutType type);
+  void RecordDefer();
+
+  bool is_deferred_ = false;
+
+  scoped_refptr<net::IOBuffer> read_buffer_;
+  base::OneShotTimer timer_;
+
+  const scoped_ptr<net::URLRequest> request_;
+  scoped_ptr<ResourceThrottle> throttle_;
+
+  base::Closure completion_callback_;
+
+  base::WeakPtrFactory<AsyncRevalidationDriver> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(AsyncRevalidationDriver);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_LOADER_ASYNC_REVALIDATION_DRIVER_H_