sync: Support non-blocking initial sync in proto

sync/sessions/nudge_tracker.h

 // Copyright 2013 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.
 //
 // A class to track the outstanding work required to bring the client back into
 // sync with the server.
 #ifndef SYNC_SESSIONS_NUDGE_TRACKER_H_
 #define SYNC_SESSIONS_NUDGE_TRACKER_H_
 
 #include <list>
@@ skipping 44 matching lines @@
   // Takes note of a local change.
   void RecordLocalChange(ModelTypeSet types);
 
   // Takes note of a locally issued request to refresh a data type.
   void RecordLocalRefreshRequest(ModelTypeSet types);
 
   // Takes note of the receipt of an invalidation notice from the server.
   void RecordRemoteInvalidation(syncer::ModelType type,
                                 scoped_ptr<InvalidationInterface> invalidation);
 
+  // Take note that an initial sync is pending for this type.
+  void RecordInitialSyncRequired(syncer::ModelType type);
+
   // These functions should be called to keep this class informed of the status
   // of the connection to the invalidations server.
   void OnInvalidationsEnabled();
   void OnInvalidationsDisabled();
 
   // Marks |types| as being throttled from |now| until |now| + |length|.
   void SetTypesThrottledUntil(ModelTypeSet types,
                               base::TimeDelta length,
                               base::TimeTicks now);
 
@@ skipping 108 matching lines @@
   // currently in a sync cycle.
   base::TimeTicks sync_cycle_start_time_;
 
   DISALLOW_COPY_AND_ASSIGN(NudgeTracker);
 };
 
 }  // namespace sessions
 }  // namespace syncer
 
 #endif  // SYNC_SESSIONS_NUDGE_TRACKER_H_