It's shown by SaveLoadChooserDialog when files are downloaded and some
save slots are locked. One can hide that dialog to interact with
non-locked slots or cancel saves sync completely. Dialog's label shows
current sync progress.
Dialog automatically hides itself when all files are downloaded.
WARNING: right now that results in a crash!
It has its own GoogleDriveTokenRefresher and knows how to do info().
This commit also contains JSON int -> long long int fix and
CurlJsonRequest '\n' -> ' ' fix.
Alexander Tkachev