Substitute ResourceHandlers with dummy ResourceHandler while request is transferred

content/browser/renderer_host/doomed_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_RENDERER_HOST_DOOMED_RESOURCE_HANDLER_H_
+#define CONTENT_BROWSER_RENDERER_HOST_DOOMED_RESOURCE_HANDLER_H_
+#pragma once
+
+#include "base/memory/ref_counted.h"
+#include "content/browser/renderer_host/resource_handler.h"
+
+// ResourceHandler that DCHECKs on all events but canceling and failing of
+// requests while activated for a URLRequest. This is used for requests that

[darin (slow to review), 2012/01/12 06:22:52]

this second sentence is particular to the way you are using this class, but as
discussed before, this class could be used for other applications too.  i would
delete this comment.

[battre, 2012/01/13 15:52:22]

Done.

+// are paused to be transferred to a new renderer.
+class DoomedResourceHandler : public ResourceHandler {
+ public:
+  // As the DoomedResourceHandler is constructed and subsituted from code

[darin (slow to review), 2012/01/12 06:22:52]

nit: subsituted -> substituted

[battre, 2012/01/13 15:52:22]

Done.

+  // of another ResourceHandler, we need to make sure that this other handler
+  // does not lose its last reference and gets destroyed by being substituted.
+  // Therefore, we retain a reference to |old_handler| that prevents the
+  // destruction.
+  DoomedResourceHandler(ResourceHandler* old_handler);

[darin (slow to review), 2012/01/12 06:22:52]

nit: mark this "explicit"

[battre, 2012/01/13 15:52:22]

Done.

+
+  // ResourceHandler implementation:
+  virtual bool OnUploadProgress(int request_id,
+                                uint64 position,
+                                uint64 size) OVERRIDE;
+  virtual bool OnRequestRedirected(int request_id,
+                                   const GURL& new_url,
+                                   content::ResourceResponse* response,
+                                   bool* defer) OVERRIDE;
+  virtual bool OnResponseStarted(int request_id,
+                                 content::ResourceResponse* response) OVERRIDE;
+  virtual bool OnWillStart(int request_id,
+                           const GURL& url,
+                           bool* defer) OVERRIDE;
+  virtual bool OnWillRead(int request_id,
+                          net::IOBuffer** buf,
+                          int* buf_size,
+                          int min_size) OVERRIDE;
+  virtual bool OnReadCompleted(int request_id,
+                               int* bytes_read) OVERRIDE;
+  virtual bool OnResponseCompleted(int request_id,
+                                   const net::URLRequestStatus& status,
+                                   const std::string& security_info) OVERRIDE;
+  virtual void OnRequestClosed() OVERRIDE;
+  virtual void OnDataDownloaded(int request_id,
+                                int bytes_downloaded) OVERRIDE;
+
+ private:
+  virtual ~DoomedResourceHandler();
+

[darin (slow to review), 2012/01/12 06:22:52]

this comment is redundant.  don't you say the same thing above?  perhaps it is
better to keep the public one.

[battre, 2012/01/13 15:52:22]

Done.

+  // Reference to the old ResourceHandlers that were active before this one
+  // replaced them. We need to retain a reference here because we replace
+  // the old handlers while they are being executed. Replacing them without
+  // retaining the reference might delete the last reference and destroy them.
+  scoped_refptr<ResourceHandler> old_handler_;
+
+  DISALLOW_COPY_AND_ASSIGN(DoomedResourceHandler);
+};
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_DOOMED_RESOURCE_HANDLER_H_