[Sync] Replacing NULL with nullptr in code and null in comments for components/sync/

components/sync/engine_impl/cycle/sync_cycle.h

 // Copyright 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.
 
 // A class representing an attempt to synchronize the local syncable data
 // store with a sync server. A SyncCycle instance is passed as a stateful
 // bundle throughout the sync cycle.  The SyncCycle is not reused across
 // sync cycles; each cycle starts with a new one.
 
 #ifndef COMPONENTS_SYNC_ENGINE_IMPL_CYCLE_SYNC_CYCLE_H_
@@ skipping 105 matching lines @@
   StatusController* mutable_status_controller() {
     return status_controller_.get();
   }
 
  private:
   SyncCycle(SyncCycleContext* context, Delegate* delegate);
 
   // The context for this cycle, guaranteed to outlive |this|.
   SyncCycleContext* const context_;
 
-  // The delegate for this cycle, must never be NULL.
+  // The delegate for this cycle, must never be null.
   Delegate* const delegate_;
 
   // Our controller for various status and error counters.
   std::unique_ptr<StatusController> status_controller_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncCycle);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_CYCLE_SYNC_CYCLE_H_