[Sync] Add histograms for cookie jar state on Sessions commit

sync/sessions/sync_session_context.cc

Index: sync/sessions/sync_session_context.cc
diff --git a/sync/sessions/sync_session_context.cc b/sync/sessions/sync_session_context.cc
index 7cef3dfcd1f142becf97b009d4d87cb9f74777cb..d9d30983b2d57055ff6a17cf1648dab5a83e29d8 100644
--- a/sync/sessions/sync_session_context.cc
+++ b/sync/sessions/sync_session_context.cc
@@ -32,7 +32,8 @@ SyncSessionContext::SyncSessionContext(
       server_enabled_pre_commit_update_avoidance_(false),
       client_enabled_pre_commit_update_avoidance_(
           client_enabled_pre_commit_update_avoidance),
-      cookie_jar_mismatch_(false) {
+      cookie_jar_mismatch_(false),
+      cookie_jar_empty_(false) {
   std::vector<SyncEngineEventListener*>::const_iterator it;
   for (it = listeners.begin(); it != listeners.end(); ++it)
     listeners_.AddObserver(*it);