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

components/sync/driver/generic_change_processor_unittest.cc

 // Copyright 2014 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/driver/generic_change_processor.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 107 matching lines @@
 };
 
 class SyncGenericChangeProcessorTest : public testing::Test {
  public:
   // Most test cases will use this type.  For those that need a
   // GenericChangeProcessor for a different type, use |InitializeForType|.
   static const ModelType kType = PREFERENCES;
 
   SyncGenericChangeProcessorTest()
       : syncable_service_ptr_factory_(&fake_syncable_service_),
-        mock_attachment_service_(NULL),
+        mock_attachment_service_(nullptr),
         sync_client_(&sync_factory_) {}
 
   void SetUp() override {
     // Use kType by default, but allow test cases to re-initialize with whatever
     // type they choose.  Therefore, it's important that all type dependent
     // initialization occurs in InitializeForType.
     InitializeForType(kType);
   }
 
   void TearDown() override {
-    mock_attachment_service_ = NULL;
+    mock_attachment_service_ = nullptr;
     if (test_user_share_) {
       test_user_share_->TearDown();
     }
   }
 
   // Initialize GenericChangeProcessor and related classes for testing with
   // model type |type|.
   void InitializeForType(ModelType type) {
     TearDown();
     test_user_share_ = base::MakeUnique<TestUserShare>();
@@ skipping 352 matching lines @@
   SyncDataList sync_data = change_processor()->GetAllSyncData(SESSIONS);
   ASSERT_EQ(sync_data.size(), 1U);
   ASSERT_EQ("session tag 2",
             sync_data[0].GetSpecifics().session().session_tag());
   EXPECT_FALSE(SyncDataRemote(sync_data[0]).GetClientTagHash().empty());
 }
 
 }  // namespace
 
 }  // namespace syncer