[Sync] Handle reassociation of tabs where the old tab is already mapped.

components/sync_sessions/sessions_sync_manager.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/sync_sessions/sessions_sync_manager.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/format_macros.h"
@@ skipping 846 matching lines @@
                    << new_tab_id;
 
           // The specifics from the SyncData are immutable. Create a mutable
           // copy to hold the rewritten ids.
           sync_pb::SessionSpecifics rewritten_specifics(specifics);
           rewritten_specifics.mutable_tab()->set_tab_id(new_tab_id);
           session_tracker_.ReassociateLocalTab(
               rewritten_specifics.tab_node_id(), new_tab_id);
           UpdateTrackerWithSpecifics(rewritten_specifics,
                                      remote.GetModifiedTime());
-
-          session_tracker_.ReassociateLocalTab(
-              rewritten_specifics.tab_node_id(), new_tab_id);
         }
       }
     }
   }
 
   // Cleanup all foreign sessions, since orphaned tabs may have been added after
   // the header.
   std::vector<const SyncedSession*> sessions;
   session_tracker_.LookupAllForeignSessions(&sessions,
                                             SyncedSessionTracker::RAW);
@@ skipping 410 matching lines @@
 }
 
 // static
 std::string SessionsSyncManager::TagHashFromSpecifics(
     const sync_pb::SessionSpecifics& specifics) {
   return syncer::GenerateSyncableHash(syncer::SESSIONS,
                                       TagFromSpecifics(specifics));
 }
 
 };  // namespace sync_sessions