[Sync] Add sync api support for context changes

chrome/browser/sync/glue/shared_change_processor.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_SHARED_CHANGE_PROCESSOR_H_
 #define CHROME_BROWSER_SYNC_GLUE_SHARED_CHANGE_PROCESSOR_H_
 
 #include "base/location.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 69 matching lines @@
   // GenericChangeProcessor stubs (with disconnect support).
   // Should only be called on the same thread the datatype resides.
   virtual int GetSyncCount();
   virtual syncer::SyncError ProcessSyncChanges(
       const tracked_objects::Location& from_here,
       const syncer::SyncChangeList& change_list);
   virtual syncer::SyncDataList GetAllSyncData(syncer::ModelType type) const;
   virtual syncer::SyncError GetAllSyncDataReturnError(
       syncer::ModelType type,
       syncer::SyncDataList* data) const;
+  virtual syncer::SyncError UpdateDataTypeContext(syncer::ModelType type,
+                                                  const std::string& context);
   virtual bool SyncModelHasUserCreatedNodes(bool* has_nodes);
   virtual bool CryptoReadyIfNecessary();
 
   // Register |generic_change_processor_| as the change processor for the
   // current type on |model_safe_group|.
   // Does nothing if |disconnected_| is true.
   virtual void ActivateDataType(syncer::ModelSafeGroup model_safe_group);
 
   virtual syncer::SyncError CreateAndUploadError(
       const tracked_objects::Location& location,
@@ skipping 26 matching lines @@
   GenericChangeProcessor* generic_change_processor_;
 
   DataTypeErrorHandler* error_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(SharedChangeProcessor);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_SHARED_CHANGE_PROCESSOR_H_