[Sync] Have configuration specify which datatypes are ready to sync

chrome/browser/sync/glue/sync_backend_host.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_SYNC_BACKEND_HOST_H_
 #define CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 115 matching lines @@
   virtual scoped_ptr<base::Thread> Shutdown(syncer::ShutdownReason reason) = 0;
 
   // Removes all current registrations from the backend on the
   // InvalidationService.
   virtual void UnregisterInvalidationIds() = 0;
 
   // Changes the set of data types that are currently being synced.
   // The ready_task will be run when configuration is done with the
   // set of all types that failed configuration (i.e., if its argument
   // is non-empty, then an error was encountered).
-  void ConfigureDataTypes(
+  // Returns the set of types that are ready to start without needing any
+  // further sync activity.
+  // BackendDataTypeConfigurer implementation.
+  syncer::ModelTypeSet ConfigureDataTypes(
       syncer::ConfigureReason reason,
       const DataTypeConfigStateMap& config_state_map,
       const base::Callback<void(syncer::ModelTypeSet, syncer::ModelTypeSet)>&
           ready_task,
       const base::Callback<void()>& retry_callback) override = 0;
 
   // Turns on encryption of all present and future sync data.
   virtual void EnableEncryptEverything() = 0;
 
   // Called on |frontend_loop_| to obtain a handle to the UserShare needed for
@@ skipping 66 matching lines @@
   virtual void DisableDirectoryTypeDebugInfoForwarding() = 0;
 
   virtual base::MessageLoop* GetSyncLoopForTesting() = 0;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHost);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_H_