Race Create vs SendRequest on cache misses.

net/disk_cache/pending_create_entry.h

+// Copyright (c) 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 NET_DISK_CACHE_PENDING_CREATE_ENTRY_H_
+#define NET_DISK_CACHE_PENDING_CREATE_ENTRY_H_
+
+#include <string>
+
+#include "base/memory/weak_ptr.h"
+#include "net/base/completion_callback.h"
+
+namespace disk_cache {
+
+class Backend;
+class Entry;
+
+// Create an entry representing a create that is in flight, without blocking.
+// When the entry pointer is no longer needed, its Close or Doom method should
+// be called. If operations are performed on this entry before the real entry
+// has been created, operations may return net::ERR_CACHE_CREATE_RACE_FAILED.

[rvargas (doing something else), 2013/01/23 22:04:09]

If we return an "entry" synchronously, the caller should be able to use it
immediately no matter what. Returning a delayed error because some work has not
been done is not nice.

Again, I don't think we should be "racing" the operations this way. It changes
behavior from what should be currently a rare event (a real error after the
transaction has started) to a common event (whoops, I didn't finish in time).

+int PendingCreateEntry(Backend* backend, const std::string& key, Entry** entry);
+
+}  // namespace disk_cache
+
+#endif  // NET_DISK_CACHE_PENDING_CREATE_ENTRY_H_