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

components/sync/engine_impl/commit.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.
 
 #include "components/sync/engine_impl/commit.h"
 
 #include <utility>
 
 #include "base/metrics/sparse_histogram.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 30 matching lines @@
                      CommitProcessor* commit_processor,
                      ExtensionsActivity* extensions_activity) {
   // Gather per-type contributions.
   ContributionMap contributions;
   commit_processor->GatherCommitContributions(requested_types, max_entries,
                                               cookie_jar_mismatch,
                                               cookie_jar_empty, &contributions);
 
   // Give up if no one had anything to commit.
   if (contributions.empty())
-    return NULL;
+    return nullptr;
 
   sync_pb::ClientToServerMessage message;
   message.set_message_contents(sync_pb::ClientToServerMessage::COMMIT);
   message.set_share(account_name);
 
   sync_pb::CommitMessage* commit_message = message.mutable_commit();
   commit_message->set_cache_guid(cache_guid);
 
   // Set extensions activity if bookmark commits are present.
   ExtensionsActivity::Records extensions_activity_buffer;
@@ skipping 46 matching lines @@
 
   DVLOG(1) << "Sending commit message.";
 
   CommitRequestEvent request_event(base::Time::Now(),
                                    message_.commit().entries_size(),
                                    request_types, message_);
   cycle->SendProtocolEvent(request_event);
 
   TRACE_EVENT_BEGIN0("sync", "PostCommit");
   const SyncerError post_result = SyncerProtoUtil::PostClientToServerMessage(
-      &message_, &response_, cycle, NULL);
+      &message_, &response_, cycle, nullptr);
   TRACE_EVENT_END0("sync", "PostCommit");
 
   // TODO(rlarocque): Use result that includes errors captured later?
   CommitResponseEvent response_event(base::Time::Now(), post_result, response_);
   cycle->SendProtocolEvent(response_event);
 
   if (post_result != SYNCER_OK) {
     LOG(WARNING) << "Post commit failed";
     return post_result;
   }
@@ skipping 46 matching lines @@
 
 void Commit::CleanUp() {
   for (ContributionMap::const_iterator it = contributions_.begin();
        it != contributions_.end(); ++it) {
     it->second->CleanUp();
   }
   cleaned_up_ = true;
 }
 
 }  // namespace syncer