Try again: Check blockfile size before attempting to read the header.

net/disk_cache/block_files.h

 // Copyright (c) 2006-2008 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.
 
 // See net/disk_cache/disk_cache.h for the public interface.
 
 #ifndef NET_DISK_CACHE_BLOCK_FILES_H__
 #define NET_DISK_CACHE_BLOCK_FILES_H__
 
 #include <vector>
 
 #include "net/disk_cache/addr.h"
 #include "net/disk_cache/mapped_file.h"
+#include "testing/gtest/include/gtest/gtest_prod.h"
 
 namespace disk_cache {
 
 class EntryImpl;
 
 // This class handles the set of block-files open by the disk cache.
 class BlockFiles {
  public:
   explicit BlockFiles(const std::wstring& path)
       : init_(false), zero_buffer_(NULL), path_(path) {}
@@ skipping 44 matching lines @@
   bool FixBlockFileHeader(MappedFile* file);
 
   // Returns the filename for a given file index.
   std::wstring Name(int index);
 
   bool init_;
   char* zero_buffer_;  // Buffer to speed-up cleaning deleted entries.
   std::wstring path_;  // Path to the backing folder.
   std::vector<MappedFile*> block_files_;  // The actual files.
 
+  FRIEND_TEST(DiskCacheTest, BlockFiles_ZeroSizeFile);
+
   DISALLOW_EVIL_CONSTRUCTORS(BlockFiles);
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_BLOCK_FILES_H__