Asynchronous initialization in Simple Index.

net/disk_cache/simple/simple_disk_format.h

Index: net/disk_cache/simple/simple_disk_format.h
diff --git a/net/disk_cache/simple/simple_disk_format.h b/net/disk_cache/simple/simple_disk_format.h
index 18dfe9661ad00402c6407254dc58e831d4e48e33..2e69f878cd21913eafaedec9d0011a154bb40eb5 100644
--- a/net/disk_cache/simple/simple_disk_format.h
+++ b/net/disk_cache/simple/simple_disk_format.h
@@ -59,6 +59,9 @@ namespace SimpleIndexFile {
     uint64 cache_size;  // Total cache storage size in bytes.
   };
 
+  // TODO(felipeg): At some point we should consider using a protobuffer.  See
+  // that we are re-implementing most of protobuffer's functionality such as
+  // Serialize and Merge.
   // We must keep this struct a POD.
   struct EntryMetadata {
     EntryMetadata();
@@ -70,12 +73,20 @@ namespace SimpleIndexFile {
     std::string GetHashKey() const;
     void SetLastUsedTime(const base::Time& last_used_time_p);
 
+    // Serialize the data from |in_entry_metadata| and appends the bytes in
+    // |out_buffer|. The serialization is platform dependent since it simply
+    // writes the whole struct from memory into the given buffer.
     static void Serialize(const EntryMetadata& in_entry_metadata,
                           std::string* out_buffer);
 
     static void DeSerialize(const char* in_buffer,
                             EntryMetadata* out_entry_metadata);
 
+    // Merge two EntryMetadata instances.
+    // The existing valid data in |out_entry_metadata| will prevail.
+    static void Merge(const EntryMetadata& entry_metadata,
+                      EntryMetadata* out_entry_metadata);
+
     char hash_key[kEntryHashKeySize];  // Not a c_string, not null terminated.
 
     // This is the serialized format from Time::ToInternalValue().