OS: All

What steps will reproduce the problem?
(1) Start using //components/leveldb_proto

What is the expected result?
It works fine.

What happens instead?
It works fine, but there is some overhead related to storing data in LevelDB, particularly for things that only write out once or read once, etc.

Notes:
It should be possible to provide the same public interface as //components/leveldb_proto/proto_database.h but instead of being backed by LevelDB, it should be backed by something simple.

A)
One idea would be for a database with the proto message Foo have something like:
###
message FooDB {
  map<string, Foo> foos;
}
###

and serialize that to disk as a single file. (Note, if we would need backwards compatibility, we could use:

###
message FooEntry {
  // Required.
  optional string key;
  // Required.
  optional Foo foo;
}

message FooDB {
  repeated FooEntry foos;
}
###

However, that is already what will happen on the wire with the new format in proto3, so I think we don't have to deal with that.

Reading would require reading all fields, and writing would require writing the whole file.

B)
For databases with known few items, another solution could be to have a single file per unique key.