Worker changes to prepare for lock-free shutdown.

sync/internal_api/public/engine/passive_model_worker.h

Index: sync/internal_api/public/engine/passive_model_worker.h
diff --git a/sync/internal_api/public/engine/passive_model_worker.h b/sync/internal_api/public/engine/passive_model_worker.h
index a6ea011dd71091712e885fe2ecef76a6b70a432d..f834c833c75f1ce5e7bc8c270c84b2ca8eabab7e 100644
--- a/sync/internal_api/public/engine/passive_model_worker.h
+++ b/sync/internal_api/public/engine/passive_model_worker.h
@@ -22,13 +22,17 @@ namespace syncer {
 // thread).
 class SYNC_EXPORT PassiveModelWorker : public ModelSafeWorker {
  public:
-  explicit PassiveModelWorker(const base::MessageLoop* sync_loop);
+  explicit PassiveModelWorker(const base::MessageLoop* sync_loop,
+                              WorkerLoopDestructionObserver* observer);
 
   // ModelSafeWorker implementation. Called on the sync thread.
-  virtual SyncerError DoWorkAndWaitUntilDone(
-      const WorkCallback& work) OVERRIDE;
+  virtual void RegisterForLoopDestruction() OVERRIDE;
   virtual ModelSafeGroup GetModelSafeGroup() OVERRIDE;
 
+ protected:
+  virtual SyncerError DoWorkAndWaitUntilDoneImpl(
+      const WorkCallback& work) OVERRIDE;
+
  private:
   virtual ~PassiveModelWorker();