[Sync] Add logic to reassociate tab nodes after restart.

chrome/browser/sync/glue/session_model_associator.h

Index: chrome/browser/sync/glue/session_model_associator.h
diff --git a/chrome/browser/sync/glue/session_model_associator.h b/chrome/browser/sync/glue/session_model_associator.h
index 615a1d1d7d505f4a428999d6c0ba8c033681b3dd..47626de4967754bcc0755764c5a6c73b0b94cfe6 100644
--- a/chrome/browser/sync/glue/session_model_associator.h
+++ b/chrome/browser/sync/glue/session_model_associator.h
@@ -108,10 +108,10 @@ class SessionModelAssociator
   // Reassociates a single tab with the sync model. Will check if the tab
   // already is associated with a sync node and allocate one if necessary.
   // |error| gets set if any association error occurred.
+  // |tab| will be updated with sync id if necessary.
   // Returns: false if the local session's sync nodes were deleted and
   // reassociation is necessary, true otherwise.
-  bool AssociateTab(const SyncedTabDelegate& tab,
-                    syncer::SyncError* error);
+  bool AssociateTab(SyncedTabDelegate* const tab, syncer::SyncError* error);
 
   // Load any foreign session info stored in sync db and update the sync db
   // with local client data. Processes/reuses any sync nodes owned by this
@@ -329,6 +329,9 @@ class SessionModelAssociator
   // invalid url's.
   bool TabHasValidEntry(const SyncedTabDelegate& tab) const;
 
+  // Update the tab id of the node associated with |sync_id| to |new_tab_id|.
+  void UpdateTabIdIfNecessary(int64 sync_id, SessionID::id_type new_tab_id);
+
   // For testing only.
   void QuitLoopForSubtleTesting();