[Sync] Have SBH tell SyncManager which types to purge

chrome/browser/sync/glue/sync_backend_registrar.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_REGISTRAR_H_
 #define CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_REGISTRAR_H_
 
 #include <map>
 #include <vector>
 
@@ skipping 25 matching lines @@
 // events to the right processors.
 class SyncBackendRegistrar : public syncer::SyncManager::ChangeDelegate,
                              public syncer::WorkerLoopDestructionObserver {
  public:
   // |name| is used for debugging.  Does not take ownership of |profile| or
   // |sync_loop|.  Must be created on the UI thread.
   SyncBackendRegistrar(const std::string& name,
                        Profile* profile,
                        base::MessageLoop* sync_loop);
 
-  // Informs the SyncBackendRegistrar of the currently enabled set of types.
-  // These types will be placed in the passive group.  This function should be
-  // called exactly once during startup.
-  void SetInitialTypes(syncer::ModelTypeSet initial_types);
-
   // SyncBackendRegistrar must be destroyed as follows:
   //
   //   1) On the sync thread, call OnSyncerShutdownComplete() after
   //      the syncer is shutdown.
   //   2) Meanwhile, on the UI thread, call StopOnUIThread(), which
   //      blocks until OnSyncerShutdownComplete() is called.
   //   3) Destroy the SyncBackendRegistrar.
   //
   // This is to handle the complicated shutdown requirements of the
   // UIModelWorker (since the UI thread is both the main thread and a
   // thread which the syncer pushes changes to).
   virtual ~SyncBackendRegistrar();
 
+  // Informs the SyncBackendRegistrar of the currently enabled set of types.
+  // These types will be placed in the passive group.  This function should be
+  // called exactly once during startup.
+  void SetInitialTypes(syncer::ModelTypeSet initial_types);
+
   // Returns whether or not we are currently syncing encryption keys.
   // Must be called on the UI thread.
   bool IsNigoriEnabled() const;
 
   // Removes all types in |types_to_remove| from the routing info and
   // adds all the types in |types_to_add| to the routing info that are
   // not already there (initially put in the passive group).
   // |types_to_remove| and |types_to_add| must be disjoint.  Returns
   // the set of newly-added types.  Must be called on the UI thread.
   syncer::ModelTypeSet ConfigureDataTypes(
       syncer::ModelTypeSet types_to_add,
       syncer::ModelTypeSet types_to_remove);
 
+  // Returns the set of enabled types as of the last configuration. Note that
+  // this might be different from the current types in the routing info due
+  // to DeactiveDataType being called separately from ConfigureDataTypes.
+  syncer::ModelTypeSet GetLastConfiguredTypes() const;
+
   // Must be called from the UI thread. (See destructor comment.)
   void StopOnUIThread();
 
   // Must be called from the sync thread. (See destructor comment.)
   void OnSyncerShutdownComplete();
 
   // Activates the given data type (which should belong to the given
   // group) and starts the given change processor.  Must be called
   // from |group|'s native thread.
   void ActivateDataType(syncer::ModelType type,
@@ skipping 66 matching lines @@
   // case, we'll destroy on demand *after* routing any dependent types
   // to syncer::GROUP_PASSIVE, so that the syncapi doesn't call into garbage.
   // If a key is present, it means at least one ModelType that routes
   // to that model safe group is being synced.
   WorkerMap workers_;
   syncer::ModelSafeRoutingInfo routing_info_;
 
   // The change processors that handle the different data types.
   std::map<syncer::ModelType, ChangeProcessor*> processors_;
 
+  // The types that were enabled as of the last configuration. Updated on each
+  // call to ConfigureDataTypes as well as SetInitialTypes.
+  syncer::ModelTypeSet last_configured_types_;
+
   DISALLOW_COPY_AND_ASSIGN(SyncBackendRegistrar);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_REGISTRAR_H_