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

sync/sessions/sync_session_context.h

Index: sync/sessions/sync_session_context.h
diff --git a/sync/sessions/sync_session_context.h b/sync/sessions/sync_session_context.h
index 94129ce9cee033d9b0815e1056b514852f9ece22..8bd00913a467a213411803c14f290e757f12e2d6 100644
--- a/sync/sessions/sync_session_context.h
+++ b/sync/sessions/sync_session_context.h
@@ -20,6 +20,7 @@
 #pragma once
 
 #include <map>
+#include <queue>
 #include <string>
 
 #include "base/gtest_prod_util.h"
@@ -27,6 +28,7 @@
 #include "base/time.h"
 #include "sync/engine/model_safe_worker.h"
 #include "sync/engine/syncer_types.h"
+#include "sync/engine/traffic_logger.h"
 #include "sync/sessions/debug_info_getter.h"
 
 namespace syncable {
@@ -123,6 +125,10 @@ class SyncSessionContext {
   // new throttled types this will remain constant through out the sync cycle.
   syncable::ModelTypeSet GetThrottledTypes() const;
 
+  std::queue<TrafficRecord>* traffic_recorder() {
+    return &traffic_recorder_;
+  }
+
  private:
   typedef std::map<syncable::ModelType, base::TimeTicks> UnthrottleTimes;
 
@@ -177,6 +183,8 @@ class SyncSessionContext {
   // unthrottled.
   UnthrottleTimes unthrottle_times_;
 
+  std::queue<browser_sync::TrafficRecord> traffic_recorder_;
+
   DISALLOW_COPY_AND_ASSIGN(SyncSessionContext);
 };