sync: Implement disabling of non blocking types

sync/internal_api/sync_core.h

 // Copyright 2014 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 SYNC_INTERNAL_API_PUBLIC_SYNC_CORE_H_
 #define SYNC_INTERNAL_API_PUBLIC_SYNC_CORE_H_
 
 #include "base/basictypes.h"
 #include "base/memory/weak_ptr.h"
 #include "base/sequenced_task_runner.h"
@@ skipping 18 matching lines @@
   explicit SyncCore(ModelTypeRegistry* model_type_registry);
   ~SyncCore();
 
   // Initializes the connection between the sync core and its delegate on the
   // sync client's thread.
   void ConnectSyncTypeToCore(
     syncer::ModelType type,
     scoped_refptr<base::SequencedTaskRunner> datatype_task_runner,
     base::WeakPtr<NonBlockingTypeProcessor> sync_client);
 
+  // Disconnects the syncer from the model and stops syncing the type.
+  //
+  // By the time this is called, the model thread should have already
+  // invalidated the WeakPtr it sent to us in the connect request.  Any
+  // messages sent to that NonBlockingTypeProcessor will not be recived.
+  //
+  // This is the sync thread's chance to clear state associated with the type.
+  // It also causes the syncer to stop requesting updates for this type, and to
+  // abort any in-progress commit requests.
+  void Disconnect(ModelType type);
+
   base::WeakPtr<SyncCore> AsWeakPtr();
 
  private:
   ModelTypeRegistry* model_type_registry_;
   base::WeakPtrFactory<SyncCore> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncCore);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_SYNC_CORE_H_