RFC: use some in-memory state in SimpleCache to quickly cache-miss some CantConditionalize cases

net/disk_cache/simple/simple_entry_impl.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_SIMPLE_SIMPLE_ENTRY_IMPL_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_IMPL_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 65 matching lines @@
                   const base::FilePath& path,
                   uint64_t entry_hash,
                   OperationsMode operations_mode,
                   SimpleBackendImpl* backend,
                   net::NetLog* net_log);
 
   void SetActiveEntryProxy(
       std::unique_ptr<ActiveEntryProxy> active_entry_proxy);
 
   // Adds another reader/writer to this entry, if possible, returning |this| to
-  // |entry|.
-  int OpenEntry(Entry** entry, const CompletionCallback& callback);
+  // |entry|.  |oracle| is permitted to be a null callback.
+  int OpenEntry(Entry** entry,
+                const Backend::OracleCallback& oracle,
+                const CompletionCallback& callback);
 
   // Creates this entry, if possible. Returns |this| to |entry|.
   int CreateEntry(Entry** entry, const CompletionCallback& callback);
 
   // Identical to Backend::Doom() except that it accepts a CompletionCallback.
   int DoomEntry(const CompletionCallback& callback);
 
   const std::string& key() const { return key_; }
   uint64_t entry_hash() const { return entry_hash_; }
 
   // The key is not a constructor parameter to the SimpleEntryImpl, because
   // during cache iteration, it's necessary to open entries by their hash
   // alone. In that case, the SimpleSynchronousEntry will read the key from disk
   // and it will be set.
   void SetKey(const std::string& key);
 
   // From Entry:
   void Doom() override;
   void Close() override;
   std::string GetKey() const override;
   base::Time GetLastUsed() const override;
   base::Time GetLastModified() const override;
   int32_t GetDataSize(int index) const override;
+  void SetOracleByte(uint8_t) override;
   int ReadData(int stream_index,
                int offset,
                net::IOBuffer* buf,
                int buf_len,
                const CompletionCallback& callback) override;
   int WriteData(int stream_index,
                 int offset,
                 net::IOBuffer* buf,
                 int buf_len,
                 const CompletionCallback& callback,
@@ skipping 280 matching lines @@
   // 1 on disk, to reduce the number of file descriptors and save disk space.
   // This strategy allows stream 1 to change size easily. Since stream 0 is only
   // used to write HTTP headers, the memory consumption of keeping it in memory
   // is acceptable.
   scoped_refptr<net::GrowableIOBuffer> stream_0_data_;
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_IMPL_H_