I *my* opinion, yes. Since this would be consistent.
I believe that the reason for using indenting with four spaces is that those lines continues from the ones above (since the code doesn't fit on one line), an example: https://github.com/biggert/pdf.js/blob/94ce3533075bf36ef3d94cd488ee48f5fbe48648/src/core/pdf_manager.js#L195.