Issue
When using upload_from_file and download_to_file to manipulate large files, it's hard to tell whether any progress is being made and whether the functions are suited for such a case. Both reference google-resumable-media as an option for more fine-grain control, but aren't clear about when this fine-grained control may be needed.

Suggestions

• Documentation for _do_upload mentions use of resumable media requests over a size threshold. Including this in upload_from_file and download_to_file would make it clear that these functions are suited for large file upload/download
• Alternatively, explicitly state that functions will not timeout or run into OOM issues due to large file size.