[Sync] Moved tab_node_id tracking to session object and improved foreign session garbage collection.

chrome/browser/sync/glue/session_sync_test_helper.h

Index: chrome/browser/sync/glue/session_sync_test_helper.h
diff --git a/chrome/browser/sync/glue/session_sync_test_helper.h b/chrome/browser/sync/glue/session_sync_test_helper.h
index 64a76c84775ef8ca7c1de2cd57ceebe53e577b69..c3fa6e1aecd4207c6d8edd81aadcd4645e82fc17 100644
--- a/chrome/browser/sync/glue/session_sync_test_helper.h
+++ b/chrome/browser/sync/glue/session_sync_test_helper.h
@@ -42,6 +42,12 @@ class SessionSyncTestHelper {
                          int tab_id,
                          sync_pb::SessionSpecifics* tab_base);
 
+  void BuildTabSpecifics(const std::string& tag,

[Nicolas Zea, 2016/04/12 20:38:03]

This entire file should really have comments, but at least could we add some
distinguishing this method from the one above?

[skym, 2016/04/12 22:12:14]

Done.

+                         int window_id,
+                         int tab_id,
+                         int tab_node_id,
+                         sync_pb::SessionSpecifics* tab_base);
+
   sync_pb::SessionSpecifics BuildForeignSession(
       const std::string& tag,
       const std::vector<SessionID::id_type>& tab_list,