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

components/sync/driver/sync_api_component_factory.h

Index: components/sync/driver/sync_api_component_factory.h
diff --git a/components/sync/driver/sync_api_component_factory.h b/components/sync/driver/sync_api_component_factory.h
index f55e55979c6c9495b0c3d422a82000b5e4b74ae3..d6ee81589c08d2aab0299d2b462df4bc1a21e7b2 100644
--- a/components/sync/driver/sync_api_component_factory.h
+++ b/components/sync/driver/sync_api_component_factory.h
@@ -118,7 +118,7 @@ class SyncApiComponentFactory {
   // |model_type| is the model type this AttachmentService will be used with.
   //
   // |delegate| is optional delegate for AttachmentService to notify about
-  // asynchronous events (AttachmentUploaded). Pass NULL if delegate is not
+  // asynchronous events (AttachmentUploaded). Pass null if delegate is not
   // provided. AttachmentService doesn't take ownership of delegate, the pointer
   // must be valid throughout AttachmentService lifetime.
   virtual std::unique_ptr<AttachmentService> CreateAttachmentService(