[Sync] Avoid unregistering object IDs on shutdown

sync/notifier/sync_notifier_helper.h

Index: sync/notifier/sync_notifier_helper.h
diff --git a/sync/notifier/sync_notifier_helper.h b/sync/notifier/sync_notifier_helper.h
index 28ff187e6798228ec63f046a9176a02e49b9479e..0628528e94fef8427b69366b200e89e1329e44d4 100644
--- a/sync/notifier/sync_notifier_helper.h
+++ b/sync/notifier/sync_notifier_helper.h
@@ -6,32 +6,49 @@
 #define SYNC_NOTIFIER_SYNC_NOTIFIER_HELPER_H_
 
 #include <map>
+#include <string>
 
 #include "base/basictypes.h"
 #include "base/observer_list.h"
+#include "base/threading/thread_checker.h"
 #include "sync/notifier/invalidation_util.h"
 #include "sync/notifier/object_id_payload_map.h"
 #include "sync/notifier/sync_notifier_observer.h"
 
+namespace invalidation {
+class ObjectId;
+}  // namespace invalidation
+
 namespace syncer {
 
-// A helper class for classes that want to implement the SyncNotifier interface.
-// It helps keep track of registered handlers and which object ID registrations
-// are associated with which handlers, so implementors can just reuse the logic
-// here to dispatch invalidations and other interesting notifications.
+// A helper class for classes that want to implement the SyncNotifier
+// interface.  It helps keep track of registered handlers and which object ID
+// registrations are associated with which handlers, so implementors can just
+// reuse the logic here to dispatch invalidations and other interesting
+// notifications.
 class SyncNotifierHelper {
  public:
   SyncNotifierHelper();
   ~SyncNotifierHelper();
 
-  // Updates the set of ObjectIds associated with a given |handler|. Passing an
-  // empty ObjectIdSet will unregister |handler|. The return value is an
-  // ObjectIdSet containing values for all existing handlers.
-  ObjectIdSet UpdateRegisteredIds(SyncNotifierObserver* handler,
-                                  const ObjectIdSet& ids);
+  // Sets the handler for the given name.  Pass in NULL for |handler| if you
+  // want to remove the handler for the given name.  (This doesn't unregister
+  // the IDs for the given name, though.)  A handler must be set for at most
+  // one name.
+  void SetHandler(const std::string& handler_name,
+                  SyncNotifierObserver* handler);
+
+  // Updates the set of ObjectIds associated with a given handler (via
+  // its name).  An ID must be registered for at most one handler.
+  void UpdateRegisteredIds(const std::string& handler_name,
+                           const ObjectIdSet& ids);
+
+  // Returns the set of IDs that are registered to a handler.
+  ObjectIdSet GetAllRegisteredIds() const;
 
   // Helper that sorts incoming invalidations into a bucket for each handler
-  // and then dispatches the batched invalidations to the corresponding handler.
+  // and then dispatches the batched invalidations to the corresponding
+  // handler.
   void DispatchInvalidationsToHandlers(const ObjectIdPayloadMap& id_payloads,
                                        IncomingNotificationSource source);
 
@@ -39,13 +56,24 @@ class SyncNotifierHelper {
   void EmitOnNotificationsEnabled();
   void EmitOnNotificationsDisabled(NotificationsDisabledReason reason);
 
+  // Needed for death tests.
+  void DetachFromThreadForTest();
+
  private:
-  typedef std::map<invalidation::ObjectId,
-                   SyncNotifierObserver*,
-                   ObjectIdLessThan> ObjectIdHandlerMap;
+  typedef std::map<invalidation::ObjectId, std::string, ObjectIdLessThan>
+      ObjectIdNameMap;
+  typedef std::map<std::string, SyncNotifierObserver*> NameHandlerMap;
+
+  SyncNotifierObserver* HandlerNameToHandler(
+      const std::string& handler_name) const;
+
+  SyncNotifierObserver* ObjectIdToHandler(
+      const invalidation::ObjectId& id) const;
 
+  base::ThreadChecker thread_checker_;
   ObserverList<SyncNotifierObserver> handlers_;
-  ObjectIdHandlerMap id_to_handler_map_;
+  ObjectIdNameMap id_to_name_map_;
+  NameHandlerMap name_to_handler_map_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncNotifierHelper);
 };