[Sync] Remove CleanupDisabledTypes command and move purge logic into SyncManager.

sync/internal_api/sync_manager_impl.h

Index: sync/internal_api/sync_manager_impl.h
diff --git a/sync/internal_api/sync_manager_impl.h b/sync/internal_api/sync_manager_impl.h
index 75f9c337f7a24a5ca0acb78a412fa5c2f3efceaa..c6da9f3012d897d5e45c95d544a1f6ff169633ac 100644
--- a/sync/internal_api/sync_manager_impl.h
+++ b/sync/internal_api/sync_manager_impl.h
@@ -194,6 +194,7 @@ class SyncManagerImpl : public SyncManager,
   FRIEND_TEST_ALL_PREFIXES(SyncManagerTest, NudgeDelayTest);
   FRIEND_TEST_ALL_PREFIXES(SyncManagerTest, OnNotificationStateChange);
   FRIEND_TEST_ALL_PREFIXES(SyncManagerTest, OnIncomingNotification);
+  FRIEND_TEST_ALL_PREFIXES(SyncManagerTest, PurgeDisabledTypes);
 
   struct NotificationInfo {
     NotificationInfo();
@@ -241,6 +242,11 @@ class SyncManagerImpl : public SyncManager,
   // went wrong.
   bool SignIn(const SyncCredentials& credentials);
 
+  // Purge those types from |previously_enabled_types| that are no longer
+  // enabled in |currently_enabled_types|.
+  bool PurgeDisabledTypes(ModelTypeSet previously_enabled_types,
+                          ModelTypeSet currently_enabled_types);
+
   void RequestNudgeForDataTypes(
       const tracked_objects::Location& nudge_location,
       ModelTypeSet type);