A crude cut at incorporating stream 1 footer read into stream 0 read.

net/disk_cache/simple/simple_entry_impl.cc

 // 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.
 
 #include "net/disk_cache/simple/simple_entry_impl.h"
 
 #include <algorithm>
 #include <cstring>
 #include <limits>
 #include <utility>
@@ skipping 1466 matching lines @@
                                     bool truncate) {
   // Currently, stream 0 is only used for HTTP headers, and always writes them
   // with a single, truncating write. Detect these writes and record the size
   // changes of the headers. Also, support writes to stream 0 that have
   // different access patterns, as required by the API contract.
   // All other clients of the Simple Cache are encouraged to use stream 1.
   have_written_[0] = true;
   int data_size = GetDataSize(0);
   if (offset == 0 && truncate) {
     RecordHeaderSizeChange(cache_type_, data_size, buf_len);
+    // Undo some of the offset weirdness from SimpleSynchronousEntry
+    stream_0_data_->set_offset(0);
     stream_0_data_->SetCapacity(buf_len);
     memcpy(stream_0_data_->data(), buf->data(), buf_len);
     data_size_[0] = buf_len;
   } else {
     RecordUnexpectedStream0Write(cache_type_);
     const int buffer_size =
         truncate ? offset + buf_len : std::max(offset + buf_len, data_size);
-    stream_0_data_->SetCapacity(buffer_size);
+    stream_0_data_->SetCapacity(buffer_size + stream_0_data_->offset());
     // If |stream_0_data_| was extended, the extension until offset needs to be
     // zero-filled.
     const int fill_size = offset <= data_size ? 0 : offset - data_size;
     if (fill_size > 0)
       memset(stream_0_data_->data() + data_size, 0, fill_size);
     if (buf)
       memcpy(stream_0_data_->data() + offset, buf->data(), buf_len);
     data_size_[0] = buffer_size;
   }
   base::Time modification_time = base::Time::Now();
@@ skipping 23 matching lines @@
     }
     crc32s_end_offset_[stream_index] = offset + length;
   } else if (offset < crc32s_end_offset_[stream_index]) {
     // If a range for which the crc32 was already computed is rewritten, the
     // computation of the crc32 need to start from 0 again.
     crc32s_end_offset_[stream_index] = 0;
   }
 }
 
 }  // namespace disk_cache