[Sync] Store the past 10 traffic records in memory.

sync/engine/syncer_proto_util.cc

Index: sync/engine/syncer_proto_util.cc
diff --git a/sync/engine/syncer_proto_util.cc b/sync/engine/syncer_proto_util.cc
index b1ed209c7fc473c0400d1563d3262aedd51bc829..1ab227bc233b8458cb972759786a1e7d22b2cc72 100644
--- a/sync/engine/syncer_proto_util.cc
+++ b/sync/engine/syncer_proto_util.cc
@@ -10,6 +10,7 @@
 #include "sync/engine/syncer.h"
 #include "sync/engine/syncer_types.h"
 #include "sync/engine/traffic_logger.h"
+#include "sync/engine/traffic_recorder.h"
 #include "sync/protocol/service_constants.h"
 #include "sync/protocol/sync.pb.h"
 #include "sync/protocol/sync_enums.pb.h"
@@ -339,6 +340,7 @@ SyncerError SyncerProtoUtil::PostClientToServerMessage(
   syncable::Directory* dir = session->context()->directory();
 
   LogClientToServerMessage(msg);
+  session->context()->traffic_recorder()->RecordClientToServerMessage(msg);
   if (!PostAndProcessHeaders(session->context()->connection_manager(), session,
                              msg, response)) {
     // There was an error establishing communication with the server.
@@ -353,6 +355,8 @@ SyncerError SyncerProtoUtil::PostClientToServerMessage(
   }
 
   LogClientToServerResponse(*response);
+  session->context()->traffic_recorder()->RecordClientToServerResponse(
+      *response);
 
   browser_sync::SyncProtocolError sync_protocol_error;