[Sync] Add sync api support for context changes

chrome/browser/sync/glue/generic_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_GENERIC_CHANGE_PROCESSOR_H_
 #define CHROME_BROWSER_SYNC_GLUE_GENERIC_CHANGE_PROCESSOR_H_
 
 #include <vector>
 
 #include "base/compiler_specific.h"
@@ skipping 48 matching lines @@
       int64 version,
       const syncer::ImmutableChangeRecordList& changes) OVERRIDE;
   // Passes |syncer_changes_|, built in ApplyChangesFromSyncModel, onto
   // |local_service_| by way of its ProcessSyncChanges method.
   virtual void CommitChangesFromSyncModel() OVERRIDE;
 
   // syncer::SyncChangeProcessor implementation.
   virtual syncer::SyncError ProcessSyncChanges(
       const tracked_objects::Location& from_here,
       const syncer::SyncChangeList& change_list) OVERRIDE;
-
-  // Fills a list of SyncData. This should create an up to date representation
-  // of all the data known to the ChangeProcessor for |datatype|, and
-  // should match/be a subset of the server's view of that datatype.
   virtual syncer::SyncDataList GetAllSyncData(syncer::ModelType type)
       const OVERRIDE;
+  virtual syncer::SyncError UpdateDataTypeContext(
+      syncer::ModelType type,
+      const std::string& context) OVERRIDE;
 
   // Similar to above, but returns a SyncError for use by direct clients
   // of GenericChangeProcessor that may need more error visibility.
   virtual syncer::SyncError GetAllSyncDataReturnError(
       syncer::ModelType type,
       syncer::SyncDataList* data) const;
 
   // Returns the number of items for this type.
   virtual int GetSyncCountForType(syncer::ModelType type);
 
@@ skipping 50 matching lines @@
   base::WeakPtrFactory<syncer::AttachmentService>
       attachment_service_weak_ptr_factory_;
   syncer::AttachmentServiceProxy attachment_service_proxy_;
 
   DISALLOW_COPY_AND_ASSIGN(GenericChangeProcessor);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_GENERIC_CHANGE_PROCESSOR_H_