[Sync] Replacing NULL with nullptr/null throughout sync code.

chrome/browser/sync/test/integration/sync_auth_test.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 "base/macros.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
 #include "chrome/browser/signin/profile_oauth2_token_service_factory.h"
 #include "chrome/browser/sync/test/integration/bookmarks_helper.h"
@@ skipping 63 matching lines @@
   SyncAuthTest() : SyncTest(SINGLE_CLIENT), bookmark_index_(0) {}
   ~SyncAuthTest() override {}
 
   // Helper function that adds a bookmark and waits for either an auth error, or
   // for the bookmark to be committed.  Returns true if it detects an auth
   // error, false if the bookmark is committed successfully.
   bool AttemptToTriggerAuthError() {
     int bookmark_index = GetNextBookmarkIndex();
     std::string title = base::StringPrintf("Bookmark %d", bookmark_index);
     GURL url = GURL(base::StringPrintf("http://www.foo%d.com", bookmark_index));
-    EXPECT_TRUE(AddURL(0, title, url) != NULL);
+    EXPECT_TRUE(AddURL(0, title, url) != nullptr);
 
     // Run until the bookmark is committed or an auth error is encountered.
     TestForAuthError(GetSyncService(0)).Wait();
 
     GoogleServiceAuthError oauth_error =
         GetSyncService(0)->GetSyncTokenStatus().last_get_token_error;
 
     return oauth_error.state() != GoogleServiceAuthError::NONE;
   }
 
@@ skipping 195 matching lines @@
   GetFakeServer()->SetAuthenticated();
   SetOAuth2TokenResponse(kValidOAuth2Token,
                          net::HTTP_OK,
                          net::URLRequestStatus::SUCCESS);
 
   // Verify that the next sync cycle is successful, and uses the new auth token.
   ASSERT_TRUE(UpdatedProgressMarkerChecker(GetSyncService(0)).Wait());
   std::string new_token = GetSyncService(0)->GetAccessTokenForTest();
   ASSERT_NE(old_token, new_token);
 }