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

components/sync/engine_impl/syncer_unittest.cc

 // 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.
 //
 // Syncer unit tests. Unfortunately a lot of these tests
 // are outdated and need to be reworked and updated.
 
 #include "components/sync/engine_impl/syncer.h"
 
 #include <stddef.h>
@@ skipping 163 matching lines @@
 }
 
 }  // namespace
 
 class SyncerTest : public testing::Test,
                    public SyncCycle::Delegate,
                    public SyncEngineEventListener {
  protected:
   SyncerTest()
       : extensions_activity_(new ExtensionsActivity),
-        syncer_(NULL),
+        syncer_(nullptr),
         last_client_invalidation_hint_buffer_size_(10) {}
 
   // SyncCycle::Delegate implementation.
   void OnThrottled(const base::TimeDelta& throttle_duration) override {
     FAIL() << "Should not get silenced.";
   }
   void OnTypesThrottled(ModelTypeSet types,
                         const base::TimeDelta& throttle_duration) override {
     scheduler_->OnTypesThrottled(types, throttle_duration);
   }
@@ skipping 5645 matching lines @@
     EXPECT_EQ("xyz", final_monitor_records["xyz"].extension_id);
     EXPECT_EQ(2049U, final_monitor_records["ABC"].bookmark_write_count);
     EXPECT_EQ(4U, final_monitor_records["xyz"].bookmark_write_count);
   } else {
     EXPECT_TRUE(final_monitor_records.empty())
         << "Should not restore records after successful bookmark commit.";
   }
 }
 
 }  // namespace syncer