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

components/sync/engine_impl/sync_scheduler_impl.cc

 // 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.
 
 #include "components/sync/engine_impl/sync_scheduler_impl.h"
 
 #include <algorithm>
 #include <cstring>
 #include <utility>
 
@@ skipping 500 matching lines @@
       AdjustPolling(UPDATE_INTERVAL);
     }
   } else {
     HandleFailure(cycle->status_controller().model_neutral_state());
   }
 }
 
 void SyncSchedulerImpl::DoConfigurationSyncCycleJob(JobPriority priority) {
   DCHECK(CalledOnValidThread());
   DCHECK_EQ(mode_, CONFIGURATION_MODE);
-  DCHECK(pending_configure_params_ != NULL);
+  DCHECK(pending_configure_params_ != nullptr);
 
   if (!CanRunJobNow(priority)) {
     SDVLOG(2) << "Unable to run configure job right now.";
     RunAndReset(&pending_configure_params_->retry_task);
     return;
   }
 
   SDVLOG(2) << "Will run configure SyncShare with types "
             << ModelTypeSetToString(cycle_context_->GetEnabledTypes());
   std::unique_ptr<SyncCycle> cycle(SyncCycle::Build(cycle_context_, this));
@@ skipping 430 matching lines @@
 
 #undef SDVLOG_LOC
 
 #undef SDVLOG
 
 #undef SLOG
 
 #undef ENUM_CASE
 
 }  // namespace syncer