**WIP** Simple Cache: reduce seeks on stream 0 read.

net/disk_cache/simple/simple_synchronous_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_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_
 
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 63 matching lines @@
 };
 
 struct SimpleEntryCreationResults {
   explicit SimpleEntryCreationResults(SimpleEntryStat entry_stat);
   ~SimpleEntryCreationResults();
 
   SimpleSynchronousEntry* sync_entry;
   scoped_refptr<net::GrowableIOBuffer> stream_0_data;
   SimpleEntryStat entry_stat;
   uint32_t stream_0_crc32;
+  uint32_t stream_1_crc32;
   int result;
 };
 
 // Worker thread interface to the very simple cache. This interface is not
 // thread safe, and callers must ensure that it is only ever accessed from
 // a single thread between synchronization points.
 class SimpleSynchronousEntry {
  public:
   struct CRCRecord {
     CRCRecord();
@@ skipping 178 matching lines @@
   bool CreateFiles(SimpleEntryStat* out_entry_stat);
   void CloseFile(int index);
   void CloseFiles();
 
   // Read the header and key at the beginning of the file, and validate that
   // they are correct. If this entry was opened with a key, the key is checked
   // for a match. If not, then the |key_| member is set based on the value in
   // this header. Records histograms if any check is failed.
   bool CheckHeaderAndKey(int file_index);
 
+  // Read the 
+  bool ReadStream0Data(SimpleEntryStat* out_entry_stat,
+                       scoped_refptr<net::GrowableIOBuffer>* stream_0_data,
+                       uint32_t* out_stream_0_crc32);
+
   // Returns a net error, i.e. net::OK on success.
   int InitializeForOpen(SimpleEntryStat* out_entry_stat,
                         scoped_refptr<net::GrowableIOBuffer>* stream_0_data,
                         uint32_t* out_stream_0_crc32);
 
   // Writes the header and key to a newly-created stream file. |index| is the
   // index of the stream. Returns true on success; returns false and sets
   // |*out_result| on failure.
   bool InitializeCreatedFile(int index, CreateEntryResult* out_result);
 
@@ skipping 97 matching lines @@
   int64_t sparse_tail_offset_;
 
   // True if the entry was created, or false if it was opened. Used to log
   // SimpleCache.*.EntryCreatedWithStream2Omitted only for created entries.
   bool files_created_;
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_