Worker changes to prepare for lock-free shutdown.

sync/sessions/sync_session_context.h

Index: sync/sessions/sync_session_context.h
diff --git a/sync/sessions/sync_session_context.h b/sync/sessions/sync_session_context.h
index 755e574fcc4d36b6427f7119f100c51821f696ca..a6f693a8bb116c19f962b7c89e977de1c08dd3ac 100644
--- a/sync/sessions/sync_session_context.h
+++ b/sync/sessions/sync_session_context.h
@@ -76,7 +76,7 @@ class SYNC_EXPORT_PRIVATE SyncSessionContext {
     routing_info_ = routing_info;
   }
 
-  const std::vector<ModelSafeWorker*> workers() const {
+  const std::vector<scoped_refptr<ModelSafeWorker> >& workers() const {
     return workers_;
   }
 
@@ -151,7 +151,7 @@ class SYNC_EXPORT_PRIVATE SyncSessionContext {
   ModelSafeRoutingInfo routing_info_;
 
   // The set of ModelSafeWorkers.  Used to execute tasks of various threads.
-  const std::vector<ModelSafeWorker*> workers_;
+  std::vector<scoped_refptr<ModelSafeWorker> > workers_;
 
   // We use this to stuff extensions activity into CommitMessages so the server
   // can correlate commit traffic with extension-related bookmark mutations.