Gentle introduction of log backend

The goal is to be able to write short logs to the pre-allocated
memory. To do that, we want to decouple file operations from logs
behind light abstraction.

There are a couple of TODO added. I hope to fix them with next iteration
where actual memory log backend will be implemented.

Change-Id: I65e80825b1e080375efc54f35b270df1ceb17a0d
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/aos/events/logging/log_edit.cc b/aos/events/logging/log_edit.cc
index dca56bb..55b7666 100644
--- a/aos/events/logging/log_edit.cc
+++ b/aos/events/logging/log_edit.cc
@@ -48,7 +48,7 @@
     aos::logger::SpanReader span_reader(orig_path);
     CHECK(!span_reader.ReadMessage().empty()) << ": Empty header, aborting";
 
-    aos::logger::DetachedBufferWriter buffer_writer(
+    aos::logger::DetachedBufferFileWriter buffer_writer(
         FLAGS_logfile,
         std::make_unique<aos::logger::DummyEncoder>(FLAGS_max_message_size));
     {