Remove some uninitialized reads from simple cache metadata serializer.

net/disk_cache/simple/simple_disk_format.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_DISK_FORMAT_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_DISK_FORMAT_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 35 matching lines @@
 // -------------------------
 //    Repeated |size| times {
 //       struct EntryMetadata;
 //    }
 // -------------------------
 //    struct Footer;
 // -------------------------
 namespace SimpleIndexFile {
   // Simple Index File metadata is defined here.
   struct Header {
+    Header();
     uint64 initial_magic_number;
     uint32 version;
     uint64 number_of_entries;
     uint64 cache_size;  // Total cache storage size in bytes.
   };
 
   // We must keep this struct a POD.
   struct EntryMetadata {
     EntryMetadata();
     EntryMetadata(const std::string& hash_key_p,
@@ skipping 16 matching lines @@
     // If you want to make calculations/comparisons, you should use the
     // base::Time() class. Use the GetLastUsedTime() method above.
     int64 last_used_time;
 
     uint64 entry_size;  // Storage size in bytes.
   };
 
   const size_t kEntryMetadataSize = sizeof(EntryMetadata);
 
   struct Footer {
+    Footer();
     uint32 crc;
   };
 
 }  // namespace SimpleIndexFile
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_DISK_FORMAT_H_