sync: Implement disabling of non blocking types

sync/internal_api/public/sync_core_proxy.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_PROXY_H_
 #define SYNC_INTERNAL_API_PUBLIC_SYNC_CORE_PROXY_H_
 
 #include "base/memory/weak_ptr.h"
 #include "sync/internal_api/public/base/model_type.h"
 
 namespace syncer {
 
 class NonBlockingTypeProcessor;
 
 // Interface for the datatype integration logic from non-sync threads.
 //
 // See SyncCoreProxyImpl for an actual implementation.
 class SYNC_EXPORT_PRIVATE SyncCoreProxy {
  public:
   SyncCoreProxy();
   virtual ~SyncCoreProxy();
 
   // Attempts to connect a non-blocking type to the sync core.
   //
   // Must be called from the thread where the data type lives.
   virtual void ConnectTypeToCore(
       syncer::ModelType type,
       base::WeakPtr<NonBlockingTypeProcessor> type_processor) = 0;
 
+  // Tells the syncer that we're no longer interested in syncing this type.
+  //
+  // Once this takes effect, the syncer can assume that it will no longer
+  // receive commit requests for this type.  It should also stop requesting
+  // and applying updates for this type, too.
+  virtual void Disconnect(syncer::ModelType type) = 0;
+
   // Creates a clone of this SyncCoreProxy.
   virtual scoped_ptr<SyncCoreProxy> Clone() const = 0;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_SYNC_CORE_PROXY_H_