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

components/sync/driver/glue/sync_backend_host_impl_unittest.cc

 // 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.
 
 #include "components/sync/driver/glue/sync_backend_host_impl.h"
 
 #include <cstddef>
 #include <utility>
 
 #include "base/files/file_util.h"
@@ skipping 89 matching lines @@
   MOCK_METHOD1(OnActionableError, void(const SyncProtocolError& sync_error));
   MOCK_METHOD0(OnSyncConfigureRetry, void());
   MOCK_METHOD1(OnLocalSetPassphraseEncryption,
                void(const SyncEncryptionHandler::NigoriState& nigori_state));
 };
 
 class FakeSyncManagerFactory : public SyncManagerFactory {
  public:
   explicit FakeSyncManagerFactory(FakeSyncManager** fake_manager)
       : fake_manager_(fake_manager) {
-    *fake_manager_ = NULL;
+    *fake_manager_ = nullptr;
   }
   ~FakeSyncManagerFactory() override {}
 
   // SyncManagerFactory implementation.  Called on the sync thread.
   std::unique_ptr<SyncManager> CreateSyncManager(
       const std::string& /* name */) override {
     *fake_manager_ =
         new FakeSyncManager(initial_sync_ended_types_, progress_marker_types_,
                             configure_fail_types_);
     return std::unique_ptr<SyncManager>(*fake_manager_);
@@ skipping 27 matching lines @@
       case GROUP_PASSIVE:
         return new PassiveModelWorker(observer);
       default:
         return nullptr;
     }
   }
 };
 
 class SyncBackendHostTest : public testing::Test {
  protected:
-  SyncBackendHostTest() : fake_manager_(NULL) {}
+  SyncBackendHostTest() : fake_manager_(nullptr) {}
 
   ~SyncBackendHostTest() override {}
 
   void SetUp() override {
     ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
 
     SyncPrefs::RegisterProfilePrefs(pref_service_.registry());
 
     sync_prefs_ = base::MakeUnique<SyncPrefs>(&pref_service_);
     backend_ = base::MakeUnique<SyncBackendHostImpl>(
@@ skipping 654 matching lines @@
   backend_->StopSyncingForShutdown();
   // Verify that call to DeactivateNonBlockingDataType doesn't assert.
   backend_->DeactivateNonBlockingDataType(AUTOFILL);
   backend_->Shutdown(STOP_SYNC);
   backend_.reset();
 }
 
 }  // namespace
 
 }  // namespace syncer